INTERNATIONAL SCHOOL

2013 2 September 14 September

INTERNATIONAL SCHOOL OF OXIDE ELECTRONICS 2013

Manuel BIBES Frédéric PETROFF CNRS/Thales 91767 Palaiseau, France Tel +33 (0) 1 69 41 58 49 [email protected]

Direction scientifique : Giovanna Chimini Contact : Dominique Donzella tél : 04 95 26 80 40

www.iesc.univ-corse.fr

Monday 2 8h30 8h45 9h00 9h15 9h30 9h45 10h00 10h15 10h30 10h45 11h00 11h15 11h30 11h45 12h00 12h15 12h30 12H45 14h00 14h15 14h30 14h45 15h00 15h15 15h30 15h45 16h00 16h15 16h30 16h45 17h00 17h15 17h30 17h45 18h00 18h15 18h30 18h45 19h00

Tuesday 3

Wednesday 4

Thursday 5

Friday 6

Saturday 7

Theory of

BiFeO3

semiconductor

Oxide interfaces

ferroelectricity

(1,5h)

physics and devices

(theory)

(1h)

(1.5h)

B. Dkhil

Introduction to Registration Welcome and orga. details

L. Bellaiche

COFFEE

COFFEE

Sunday 8

Monday 9

Tuesday 10

Wednesday 11

Thursday 12

Basics of (ferro)-elasticity I

Novel phenomena

XPS, PES

Raman spectro.

Mossbauer

at oxide

and ARPES

for physicists II

spectroscopy

interfaces

(1h)

(1h)

(1h)

(1,5h)

(1,5h)

E. Salje

(1.5h)

O. Karis

M. Cazayous

J. Juraszek

M. Alexe

R. Pentcheva

Flexoelectric

J. Santamaria

XAS and

Superconducting

Electric-field effects

XMCD

devices

in oxides

COFFEE

COFFEE

(1h)

(1h)

(1h)

(1h)

Interfacial effects in

J. Scott

S. Valencia

J.E. Villegas

J.E. Villegas

spectroscopy COFFEE

Friday 13

Basics of

COFFEE

Symmetry and

ferroelectricity :

Electron transport

Spin transport

novel oxide

COFFEE

Oxide

COFFEE

COFFEE

COFFEE

topology I

experimental aspects

in oxide materials

(1,5h)

heterostructures

High Tc

spintronics

TEM for local

Advanced

The spin torque

M. Viret

(1,5h)

superconductors

(1.5h)

structure & chemistry

TEM techniques

Lego

J.M. Triscone

(1h)

M. Bibes

(1h)

(1h)

(1h)

B. Warot

B. Warot

J. Grollier

LUNCH

LUNCH

LUNCH

(1,5h)

(1,5h)

(1,5h)

M. Mostovoy

J.M. Triscone

S. Gariglio

J. Santamaria LUNCH

LUNCH

LUNCH

LUNCH

LUNCH

LUNCH

LUNCH

Correlations, Charge, orbital and spin ordering (1,5h)

COFFEE

COFFEE

R. Pentcheva COFFEE

Arrival

COFFEE

COFFEE

COFFEE

COFFEE

Poster

COFFEE

COFFEE

Poster

COFFEE

PFM and

Superconductivity

Polarized light for

Session

Transparent

Raman spectro.

Session

Resistive

#1

#2

switching

Symmetry and

Magnetic

MFM

background

spectro. and imaging

conducting oxides

for physicists I

topology II

oxides

(1h)

(1h)

(1h)

(1h)

(1h)

(1h)

(1,5h)

(1,5h)

P. Paruch

S. Gariglio

G. Herranz

D. Lenoble

M. Cazayous

H. Kohlstedt

M. Mostovoy

M. Viret

Ferroelectric

SrTiO3

Defects

Solar cellls

Effect of pressure on

vortices

(1h)

in oxides

Basics of

(1h)

structural properties

(1h)

G. Herranz

(1h)

(ferro)-elasticity II

A. Klein

A. Klein

(1h)

END

BREAK

of

L. Bellaiche

Ferroelectric PEEM

tunnel junctions

(1h)

(1h)

(1h)

J. Kreisel

S. Valencia

V. Garcia Memristors

Introduction to

BREAK

BREAK

BREAK

E. Salje

BREAK

BREAK

multiferroics

Symmetry and

Rare earth

CTAFM

Domain wall

Ferroelectric

Quantum critical

Inside

(1,5h)

topology III

nickelates

(1h)

transport

photovoltaics

phenomena

Nature Materials

(1h)

M. Lezaic

(1h)

(1h)

V. Garcia

(1h)

(1h)

(1h)

(1h)

J. Grollier

M. Mostovoy

M. Lezaic

P. Paruch

M. Alexe

J. Scott

A. Taroni

END

END

END

END

END

BBQ

participants END

END

BREAK

END

Saturday 14

Departure

of

participants

Institut d’Etudes Scientifiques de Cargèse 20130 Cargèse, Corse (France) - http://www.iesc.univ-corse.fr

ISOE2013 International School of Oxide Electronics Cargèse, France – September 2-14, 2013 http://sites.google.com/site/orgaisoe [email protected]

Organizing Committee Manuel Bibes (UMPhi CNRS/Thales, Palaiseau, France), co-chair Brahim Dkhil (Ecole Centrale Paris, France), co-chair Jens Kreisel (Centre de Recherche Publique Lippmann, Luxembourg) Frédéric Petroff (UMPhi CNRS/Thales, Palaiseau, France) Anne Dussart (UMPhi CNRS/Thales, Palaiseau, France))

Initiated by the progress in thin film growth since the discovery of high TC superconductors, the field of Oxide Electronics took off at the end of the 1990’s and is now growing at an exponential pace. Major breakthroughs over the last 7 or 8 years include the advent of multiferroics and the discovery of several unexpected phases at oxide interfaces, epitomized by the high-mobility two-dimensional electron gas found at the interface between two band insulators, LaAlO3 and SrTiO3. Novel physical phenomena have also been revealed in ultrathin films of ferroelectric or correlated electron systems, as well as giant responses and phase transitions induced by light or electric field, with potential for innovative devices. After ISOE2011, the 2nd Edition of the International School of Oxide Electronics aims at gathering PhD students, post-docs, young scientists and senior researchers working in Oxide Electronics for almost two weeks in the peaceful and scenic Cargèse Scientific Institute, to build up the future Oxide Electronics scientific community. Basic notions of solid-state physics (superconductivity, ferroelectricity, magnetism, optics, correlations, etc) will be recalled, but the school will also give an extended overview of the field, covering topics such as multiferroics, oxide interfaces, domain walls or manganese and nickel perovskites. Oxide-based devices (tunnel junctions, field-effect devices, memristors) will also be presented in detail, as well as key advanced characterization and computational techniques. It is our pleasure to welcome you at IESC in Cargèse for 12 days of exciting science in this exceptional location. We hope you will make the best of the technical program and of your stay here.

The organizing committee

Manuel Bibes (UMPhi CNRS/Thales, Palaiseau, France), co-chair Brahim Dkhil (Ecole Centrale Paris, France), co-chair Jens Kreisel (Centre de Recherche Publique Lippmann, Luxembourg) Frédéric Petroff (UMPhi CNRS/Thales, Palaiseau, France) Anne Dussart (UMPhi CNRS/Thales, Palaiseau, France)

The International School of Oxide Electronics 2013 is sponsored by :  CNRS  Centre de Recherche Public Gabriel Lippmann  Université de Genève  Ecole Centrale Paris  Agence Nationale de Recherche  Université Paris 7 – Denis Diderot  Bruker  Surface Technology  Crystec  Triangle de la Physique  Thales We would like to thank them all for their support.

Lecturers :  Marin Alexe (Max Planck Institute, Halle, Germany)  Laurent Bellaiche (University of Arkansas, USA)  Manuel Bibes (UMPhi CNRS/Thales, Palaiseau, France)  Maximilien Cazayous (Université Paris 7 Denis Diderot, France)  Brahim Dkhil (Ecole Centrale Paris, France)  Vincent Garcia (UMPhi CNRS/Thales, Palaiseau, France)  Stefano Gariglio (Université de Genève, Switzerland)  Julie Grollier (UMPhi CNRS/Thales, Palaiseau, France)  Gervasi Herranz (ICMAB-CSIC, Barcelona, Spain)  Jean Juraszek (Université de Rouen, France)  Olof Karis (University of Uppsala, Sweden)  Hermann Kohlstedt (University of Kiel, Germany)  Andreas Klein (University of Darmstadt, Germany)  Damien Lenoble (Centre de Recherche Lippmann, Luxemburg)  Marjana Lezaic (Institut für Festkörperforschung Jülich, Germany)  Maksym Mostovoy (University of Gröningen, the Netherlands)  Patrycja Paruch (Université de Genève, Switzerland)  Rossitza Pentcheva (University of Munich, Germany)  Eckhard Salje (University of Cambridge, UK)  Jacobo Santamaria (Universidad Complutense de Madrid, Spain)  James F. Scott (University of Cambridge, UK)  Andrea Taroni (Nature Publishing Group)  Jean-Marc Triscone (Université de Genève, Switzerland)  Sergio Valencia (Helmholtz Zentrum Bessy, Berlin, Germany)  Javier Villegas (UMPhi CNRS/Thales, Palaiseau, France)  Michel Viret (CEA SPEC, Gif-sur-Yvette, France)  Bénédicte Warot (CEMES-CNRS, Toulouse, France)

Abstracts of lectures

! Effects!of!broken!symmetry!and!nontrivial!topology!in!magnets! !! !

Maxim!Mostovoy!! ! Zernike!Institute!for!Advanced!Materials,!University!of!Groningen,!! Nijenborgh!4,!9747!AG,!Groningen,!The!Netherlands!! ! ! ! I! will! give! a! pedagogical! introduction! to! symmetry! analysis! of! physical! phenomena! in! solids.! There! is! a! deep! relation! between! macroscopic! properties! of! solids,! such! as! piezoelectricity,!! natural!optical!activity,!magnetoelectric!response!and!weak!ferromagnetism,!and!crystal!lattice! symmetry.! New! physical! effects! often! emerge! at! phase! transitions! as! a! result! of! spontaneous! symmetry! breaking! by! a! charge! or! spin! ordering.! I! will! discuss! Landau! theory! of! second"order! phase! transitions! and! its! use! for! deducing! physical! consequences! of! spontaneous! symmetry! breaking,! focusing! in! particular! on! multiferroic! and! magnetoelectric! effects! in! magnets! with! unconventional! spin! orders.! I! will! also! consider! unusual! properties! of! topological! defects! in! magnetic!orders,!such!as!domain!walls!and!skyrmions.!Remarkably,!non"trivial!topology!of!spin! textures!gives!rise!to!effective!electromagnetic!fields!responsible!for!the!fascinating!dynamics!of! charges!and!spins.!!! ! !! ! ! ! !!

!

Correlations,!charge,!spin!and!orbital!ordering! ! Rossitza!Pentcheva! ! Ludwig!Maximilians!University!Munich,!Germany!! ! ! ! Transition!metal!oxides!(TMO)!with!their!correlated!electrons!exhibit!a!set!of!fascinating!properties!such! as! magnetism,! ferroelectricity,! high! Tc! superconductivity.! This! lecture! will! address! the! challenges! in! theoretical! modelling! of! bulk! TMO.! A! central! aspect! will! be! the! interplay! of! charge,! spin! and! orbital! degrees!of!freedom!and!how!these!affect!the!ground!state!of!the!system.!As!an!example!for!an!eg!system! I! will! discuss! the! rich! phase! diagram! of! the! manganites! and! in! particular! the! role! of! electron"lattice! interactions,! doping! and! strain! to! control! the! electronic! and! magnetic! ground! state.! Furthermore,! the! orbital!and!magnetic!order!in!vanadates!and!titanates!as!t2g!systems!will!be!assessed.! Unlike! spin! and! orbital! order,! charge! order,! which! is! considered! to! be! the! origin! of! several! important! cases! of! metal"to"insulator! transition,! is! not! directly! measurable.! This! lecture! will! address! the! current! controversy!regarding!the!concept!and!definition!of!charge!order!in!TMO!systems.! ! !

!

Theory!of!Ferroelectricity! ! Laurent!Bellaiche! ! University!of!Arkansas! ! ! ! Here,! we! will! focus! on! effective! Hamiltonian! techniques,! in! order! to! understand! ferroelectricity! at! a! microscopic! level.! The! first! microscopic,! effective! Hamiltonian! approach! of! ferroelectric! materials! was! developed! in! the! mid"nineties.! Since! then,! it! has! achieved! great! successes! in! describing! various! ferroelectric! materials.! In! a! nutshell,! effective! Hamiltonian! methods! first! identify! the! most! important! degrees!of!freedom!in!a!ferroelectric!material,!and!then,!based!on!symmetry!arguments,!constructs!the! internal! energy! of! the! system! as! a! function! of! these! degrees! of! freedom! and! their! interactions.! The! coefficients! entering! the! effective! Hamiltonian! energy! are! typically! obtained! from! ab!initio! computations.!!These!techniques!are!then!used!into!Monte"Carlo!and!!molecular!dynamics!simulation!to! determine!static!and!dynamical!properties!at!finite!temperature,!respectively.! ! !Initially,!only!the!so"called!local!modes!and!strains!of!simple!bulk!systems!were!included!into!effective! Hamiltonian!schemes.!However,!later!on,!alloy!effects,!oxygen!octahedral!tiltings!and!magnetic!degrees! of! freedom! were! added! into! effective! Hamiltonian! approaches,! and! nanostructures! were! also! investigated!thanks!to!these!techniques.! ! Technical! details! about! effective! Hamiltonians! will! be! discussed.! The! understanding! of! complex! properties! and! the! discoveries! of! novel! effects! arising! from! the! use! of! these! Hamiltonians! will! also! be! discussed.! ! These! works! are! supported! and! ONR! Grants! No.! N00014"11"1"0384! and! N00014"12"1"1034,! NSF! grant! DMR"1066158,!the!Department!of!Energy,!Office!of!Basic!Energy!Sciences,!under!contract!ER"46612,!and! ARO!Grant!W911NF"12"1"0085.! ! ! ! ! ! !!

Basics of Ferroelectricity – Experimental Aspects Jean-Marc Triscone DPMC, University of Geneva, 24 quai E.-Ansermet, CH-1211 Geneva 4, Switzerland In this lecture, I will start by a general introduction on ferroelectrics describing their basic properties and some possible applications of these exciting materials. I will mention how one can probe the basic electrical properties of ferroelectric materials. I will then discuss more in detail ferroelectric thin films and heterostructures and show how strain can be used to tune the physical properties of the materials. I will briefly explain how ferroelectric domains can be probed using atomic force microscopy before to discuss the possible functional properties of domain walls and the growing interest in this new field of research. I will then move to oxide heterostructures and to the study of PbTiO3 / SrTiO3 epitaxial ferroelectric / paraelectric superlattices. Those have proven to be an exciting system. Over most of the compositional range, the structural and electrical properties can be well described by a simple Landau-theory-based electrostatic model with bulk PbTiO3 and SrTiO3 parameters [1,2]. However, as the individual layers get thinner and the number of interfaces increases, an unusual coupling between oxygen octahedral rotations and the polar mode is found leading to improper ferroelectricity [3]. Such a coupling was shown to be a possible path to the development of novel multiferroic materials [4]. These superlattices have also proven to be an ideal system to study ferroelectric domains and the role of the depolarizing field [5-7]. The results obtained in superlattices will be compared to recent investigations of the domain structure in single layers of PbTiO3. [1] M. Dawber, C. Lichtensteiger, M. Cantoni, M. Veithen, P. Ghosez, K. Johnston, K.M. Rabe, and J.-M. Triscone, Physical Review Letters 95, 177601 (2005). [2] M. Dawber, N. Stucki, C. Lichtensteiger, S. Gariglio, Ph. Ghosez, and J.-M. Triscone, Advanced Materials 19, 4153 (2007). [3] E. Bousquet, M. Dawber, N. Stucki, C. Lichtensteiger, P. Hermet, J.-M. Triscone, and Ph. Ghosez, Nature 452, 732 (2008). [4] N.A. Benedek and C.J. Fennie, Phys. Rev. Lett. 106, 107204 (2011). [5] P. Zubko, N. Stucki, C. Lichtensteiger and J.-M. Triscone, Physical Review Letters 104, 187601 (2010). [6] A. Torres-Pardo, A. Gloter, P. Zubko, N. Jecklin, C. Lichtensteiger, J.-M. Triscone and O. Stéphan, Physical Review B84, 220102(R) 2011. [7] P. Zubko, N. Jecklin, A. Torres-Pardo, P. Aguado-Puente, A. Gloter, C. Lichtensteiger, J. Junquera, O. Stéphan, and J.-M. Triscone, Nanoletters 12, 2846 (2012).

!

Magnetic!Oxides! !

Michel!Viret! ! Service!de!Physique!de!l’Etat!Condensé,!DSM/IRAMIS/SPEC,!CEA!Saclay,!France! ! ! In!this!lecture,!I!will!review!the!general!magnetic!properties!of!oxide!materials.!I!will!recall!the!basic!rules! for! magnetic! ordering! and! in! particular! the! indirect! exchange! interactions! through! the! oxygen.! I! shall! underline!the! role!of! lattice! distortions! and! charge! and! orbital! ordering.! I! will! illustrate! the! basic! rules! taking! as! two! examples! the! manganites! and! the! multiferroics.! In! the! first! family,! I! will! present! the! correlation! between! magnetic! properties! and! electrical! transport! introducing! the! colossal! magnetoresistance! effect.! Transport! properties! will! be! illustrated! through! the! models! of! magnetic! localization.! The! problem! of! phase! separation! in! these! materials! will! be! surveyed! with! a! critical! eye.! I! shall!then!illustrate!the!revival!of!the!multiferroics!through!the!example!of!BiFeO3.!A!particular!emphasis! will!be!given!to!its!magnetic!properties!and!their!correlation!to!ferroelectricity.!Finally,!I!will!underline! the!relevance!of!both!materials’!families!to!the!field!of!Spintronics.! ! !

!

Introduction!to!multiferroics! !

Marjana!Ležai"! ! Peter!Grünberg!Institut,!Forschungszentrum!Jülich,!D#52425!Jülich,!Germany! ! ! Multiferroic!materials!display!a!simultaneous!ferroelectric!and!magnetic!order!and!are!currently!one!of! the! spots! of! high! interest! in! spintronics! investigations.! The! reason! are! numerous! possible! applications! such! as! 4#bit! memory! and! possibility! of! electric! field! controlled! magnetization! (or! magnetic! field! controlled!electric!polarization).!! Designing!novel!multiferroics!with!predefined!desired!properties!is!not!an!easy!task,!due!to!an!essential!! incopatibility!of!the!physics!driving!ferroelectricity!and!that!which!drives!magnetism.!This!lecture!will!be! dedicated! to! understanding! the! difficulties! and! to! possible! ways! of! circumventing! them! within! a! framework!of!ab!initio!multiferroics!design.!Furthermore,!we!will!discuss!some!applications!of!both!bulk! and!of!multicomponent!layered!multiferroic!systems.!! !!

BiFeO3 : a driving force in the world of ferroics Brahim Dkhil Laboratoire SPMS, Ecole Centrale Paris, Chatenay-Malabry, FRANCE

Since 2003, when high quality epitaxial thin films of BiFeO3 (BFO) have been successfully made by the Ramesh group in Berkeley, the field of multiferroics has known a rapid progress punctuated by the (re-)discovery of many new physical phenomena. Indeed, because of its rich ferroic properties (elastic, electric and magnetic) existing simultaneously at room temperature, BFO has attracted a lot of attention and is currently considered as a model multiferroic. Basically, its large polarization, its antiferromagnetic order, its long period cycloidal spin modulation, its original elastic distortions arising from the coexistence of oxygen tiltings with the polar shifts and its rather low bandgap insulator (or high bandgap semiconductor) character make BFO a fantastic multifunctional system for studying interactions/couplings between these various properties. More specifically, below the Curie temperature TC|1100 K, BFO becomes ferroelectric and is described by the rhombohedral R3c space group, which allows antiphase octahedral tilting and ionic displacements from the centrosymmetric positions about and along the same cubic-like directions. Below the Néel temperature TN|640 K, it exhibits a G-type antiferromagnetic order, where the Fe magnetic moments are coupled ferromagnetically within the pseudocubic {111} planes and antiferromagnetically between neighbouring planes. In the bulk, an additional long-range cycloidal magnetic modulation is superimposed on this antiferromagnetic order, resulting in a rotation of the spin axis through the crystal with a long period O|62nm. As a result, BFO has shown promising potential applications in various fields as ferroelectric memory, energy harvesting, magnetoelectric, magnonic or spintronic devices. Moreover, BFO has a small bandgap (in contrast to normal ferroelectrics) of 2.7eV allowing charges separation resembling that occurring in p-n semiconductor junctions. Therefore, properties such as visible-light photovoltaic effect, photostriction properties, waves generation by laser illumination, electrochromism or even photocatalysis have been recently explored. Despite tremendous effort devoted to the study of BFO as film form, I will start this lecture by focusing on the bulk form by showing temperature and pressure dependences of BFO properties, highlighting the difficulties to study such system because of the effect of Bi volatility and the close energies of the pure BFO with some parasitic phases, the existence of a skin-layer which has its own phase diagram and the instabilities induced by pressure showing its potential for strain-engineering. Then, because of the strong coupling between ferroic orders (elastic, electric and magnetic) and the various structural degrees of freedom (polar and antiferrodistortive which are usually antagonist features) I will show that BFO actually exhibits a rich and highly tunable multifunctional character. More specifically I will present how misfit strain can 1) affect BFO phases allowing original mixed-phase state; 2) tune the critical temperatures of antiferromagnetic and ferroelectric transitions until bringing both close together; 3) modify the ferroelectric, dielectric and piezoelectric properties; and 4) control the magnetic properties and spin arrangements. Finally I will briefly discuss recent conductive and optical properties related to the low bandgap of BFO by showing how the physics of domain walls, as well as of ionic defects enrich the potentialities of BFO and offer novel and challenging areas of research in the world of ferroics.


         
 

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PFM and MFM From basic measurements to cutting edge applications Patrycja Paruch DPMC-MaNEP, Université de Genève, Switzerland

Scanned probe microscopy (SPM) techniques have become some of the most powerful tools available to us for the study of the fundamental and functional properties of material systems at nanoscale resolution. Based on sensitive measurements of the interaction between a sample surface and a nanofabricated, appropriately functionalized probe tip, this technique is particularly useful for locally exploring ferroelectric behaviour via piezoresponse force microscopy, and magnetic properties via magnetic force microscopy, spatially limited essentially only by the tip size. In this course, I will introduce the key aspects of image formation and analysis in each techniqe, and briefly discuss possible sources of noise and artefacts, illustrating these with examples from recent research on ferroelectric, multiferroic and spin nanostructures. I will then show the results of ongoing studies to further improve the resolution and application domain of these techniques, in particular by optimization of the probe tips with functionalized carbon nanotubes, and by accessing a wider range of frequencies via “band excitation” in both PFM and MFM imaging.

Spin transport Michel Viret Service de Physique de l’Etat Condensé, DSM/IRAMIS/SPEC, CEA Saclay, France

In this lecture, I will introduce the field of Spintronics with its recent evolution towards spin transfer and the interplay between magnetic dynamical properties and spin currents. Traditionally the field has relied on a basic device called a ‘spin valve’ composed of two ferromagnetic layers separated by a nonferromagnetic one. Depending on the relative magnetic orientation of the ferromagnetic layers, the resistance of the stack switches between low and high values, thus demonstrating the influence of charge carriers’ spins (controlled via the magnetization) on the electrical properties of the device. The non magnetic spacer layer can also be a tunneling barrier which leads to very large magnetoresistance (over 500% effects are obtained in Fe/MgO/Fe). These have been commercialized as magnetic fields sensors and memory elements where the information is stored in the magnetization. This has triggered an impressive increase in the density of data storage which largely contributed to the revolution of information technologies. 1 A more recent advance relies on the effect of a spin polarized current on ferromagnetic layers . It has indeed been demonstrated that the angular momentum lost by spin carriers as their polarization changes direction passing through differently magnetized layers is given to the local magnetization and is able to switch it. This is an important new addition to spintronics as it opens the way to a pure electrical control of magnetization in spin valves. Furthermore, spin currents can also affect the magnetization dynamics and even induce ferromagnetic resonance. Specially designed spin valves can therefore be used as integrable and agile and nano radio-frequency sources (a clear dependence of the emitted frequency with the input current intensity) much in demand for 2 applications. The early prediction and subsequent confirmation that domain walls, the regions separating different magnetic domains, can also be moved by (spin-polarized) electrical currents offers an attractive alternative in designing novel devices such as sensors and magnetic random-access memories. Indeed, domain walls are now considered as possible objects for high-speed logic, where each wall represents a single bit. In IBM’s racetrack 3 memory project, the walls can be moved with a current and the information read, either with optical techniques or electrically. Driven by these enormous prospects for technological applications, active studies of domain walls are underway worldwide. In this lecture, the different spin-transfer torques, often studied independently will be addressed. I will cover theory and experiments on magnetization reversal, domain-wall displacement and nano-oscillators. Indeed, since the first theoretical proposal on spin-transfer torque—reported by Berger and Slonczewski independently—spintransfer torque has been experimentally demonstrated in vertical magnetoresistive nano-pillars and lateral ferromagnetic nano-wires. In the former structures, an electrical current flowing vertically in the nano-pillar exerts spin torque onto the thinner ferromagnetic layer, which can be used to either reverse magnetization or generate radio-frequency. In the latter structures, an electrical current flowing laterally in the nano-wire exerts torque onto a domain wall and moves its position by rotating local magnetic moments within the wall, i.e., domain wall displacement. The theoretical understanding of magnetization dynamics during reversal as well as domain wall displacement can be understood using the conventional Landau--Lifshitz–Gilbert (LLG) equation, adding a spintorque term. Basic analytical models will be introduced which can explain the details of the spin current induced magnetization dynamics and domain wall motion mechanisms. A short overview on materials, in particular oxides, as well as potential applications will conclude the lecture.

1 2

L. Berger, Phys. Rev. B 54, 9353 (1996); J. Slonczewki, J. Magn. Magn. Mater. 159, L1 (1996).

L. Berger, J. Appl. Phys. 49, 2156 (1978) and J. Appl. Phys. 55, 1954 (1984). 3 S.S.P. Parkin, “Shiftable magnetic shift register and method of using the same,” U.S. Patent 6,834,005 (2004).

!

Ferroelectric!vortices! ! Laurent!Bellaiche! ! University!of!Arkansas! !

In 2004, the use of a first-principles-based effective Hamiltonian [1] led to the prediction of a novel structure in zero-dimensional ferroelectrics, in which the electric dipoles organize themselves to form a vortex [2]. Such structure exhibits the so-called spontaneous toroidal moment, rather than the spontaneous polarization, as its order parameter [2]. Subsequently, various original phenomena, all related to vortices, were predicted in ferroelectric nanostructures. Examples of such phenomena are: (i) that inhomogeneous static electric fields allow to efficiently control and switch the direction of the spontaneous toroidal moment [3]; (ii) the existence of a new order parameter, denoted as the hypertoroidal moment, that is associated with many complex dipolar structures (such as double-vortex states) [4]; (iii) the possible control of single and double vortex states by homogeneous electric fields, via the formation of original intermediate states [5,6]; (iv) the discovery of a new class of quantum materials (denoted as incipient ferrotoroidics), for which zero-point vibrations wash out the vortex state and yield a complex local structure [7]; (v) the existence of chiral patterns of oxygen octahedral tiltings that originate from the coupling of these tiltings with the ferroelectric vortices [8]. The purpose of this talk is to discuss some of these striking phenomena, as well as, to reveal others (if time allows). In particular, ferroelectric vortices can give rise to a novel control of magnetism in multiferroic nanodots, and the existence of spontaneous optical activity. These! works! are! supported! NSF! grant! DMR"1066158,! ARO! Grant! W911NF"12"1"0085,! the! Department!of! Energy,! Office! of! Basic! Energy! Sciences,! under! contract! ER"46612,! and! ONR! Grants! No.! N00014"11"1"0384!and!N00014"12"1"1034.!! ! [1] ``Finite-temperature properties of Pb(Zr1-xTix)O3 alloys from first-principles,'' L. Bellaiche, A. Garcia and D. Vanderbilt, Phys. Rev. Lett. 84, 5427 (2000). [2] ``Unusual phase transitions in ferroelectric nanodisks and nanorods,'' Ivan I. Naumov, L. Bellaiche and Huaxiang Fu, Nature (London) 432, 737 (2004). [3] ``Controlling Toroidal Moment by Means of an Inhomogeneous Static Field: An Ab Initio Study,'' S. Prosandeev, I. Ponomareva, I. Kornev, I. Naumov and L. Bellaiche, Phys. Rev. Lett. 96, 237601 (2006). [4]! ``Order! parameter! in! complex! dipolar! structures:! Microscopic! modeling,''! S.! Prosandeev! and! L.! Bellaiche,!Phys.!Rev.!B!77,!060101(R)!(2008).! [5]! ``Control! of! vortices! by! homogeneous! fields! in! asymmetric! low"dimensional! dipolar! systems,''! S.! Prosandeev,!!I.!Ponomareva,!I.!Kornev,!and!L.!Bellaiche,!Phys.!Rev.!Lett.!100,!047201!(2008).!! [6]! ``Controlling! double! vortex! states! in! low"dimensional! dipolar! systems,''! S.! Prosandeev! and! L.! Bellaiche,!Phys.!Rev.!Lett.!101,!097203!(2008).! [7]! ``Discovery! of! incipient! ferrotoroidics! from! atomistic! simulations,''! S.! Prosandeev,! A.! R.!Akbarzadeh! and!L.!Bellaiche,!Phys.!Rev.!Lett.!102,!257601(2009).!! [8]!``Chiral!patterns!of!tilting!of!oxygen!octahedra!in!zero"dimensional!ferroelectrics!and!multiferroics:!A! first!principle"based!study,''!David!Sichuga,!Wei!Ren,!Sergey!Prosandeev,!and!L.!Bellaiche,!Phys.!Rev.!Lett.! 104,!207603!(2010).!!

!

Introduction!in!semiconductor!physics!and!devices! !

Marin!Alexe! ! Max!Planck!Institute!of!Microstructure!Physics,!Halle,!Germany!and! University!of!Warwick,!Coventry,!UK!!! ! ! ! Historically,! ferroelectric! materials! have! been! considered! perfect! insulators! possessing! spontaneous! polarization!which!can!be!switched!with!an!external!electric!field!between!minimum!two!stable!states.! Very! seldom! ferroelectrics! have! been! regarded! as! useful! semiconductors! mostly! due! to! high! level! of! structural! and! electronic! complexity,! as! well! as! notorious! low! mobility! of! free! carriers.! Nevertheless,! interaction!between! free!carriers,!i.e.! transport!phenomena,!and! ferroelectric! polarization!has!been!at! the! core! of! new! effects! such! as! resistive! switching,! tunnel! electroresistance,! abnormal! photovoltaic! effect,!etc.! The!present!lecture!will!address!briefly!the!basics!of!semiconductor!physics,!transport!phenomena,!and! device!physics!of!ferroelectric!structures.!Basic!devices!such!as!metal"semiconductor!(Schottky)!junction,! or!field!effect!transistors!will!be!also!discussed.!! ! ! ! !!


   


 

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Electronic!Structure!of!SrTiO3! Gervasi!Herranz! Institute!of!Materials!Science!of!Barcelona!ICMAB"CSIC! Campus!de!la!UAB,!08193!Bellaterra,!Catalonia,!Spain! Email:[email protected]! Phone:!+34!93!580!18!53!(ext.!357)! ! ! SrTiO3!is!considered!to!be!the!cornerstone!material!for!the!would"be!oxide!electronics,!playing!a!similar! role!as!silicon!does!in!the!actual!conventional!semiconductor!electronics.!Such!an!interest!for!SrTiO3!is! founded! by!the! diversity!of! its! physical! properties.! For! instance,! while! in! its!stoichiometric! form! it! is! a! wide"bangap!insulator,!upon!slight!off"stoichiometry!or!by!subtle!concentrations!of!extrinsic!dopants!it! undergoes!an!insulator"to"metal!transition,!reaching!high!electron!mobilities!at!low!temperatures!(up!to! above! 105! cm2/Vs).! Interestingly,! for! a! wide! range! of! doping! amounts,! the! metallic! state! transits! to! superconductivity.!Additionally,!strain!plays!also!a!fundamental!role!in!modulating!its!properties!by,!e.g.,! driving! the! ground"state! paraelectric! state! to! polar! and! ferroelectric! behaviour.! This! remarkable! flexibility! and! ability! to! tune! its! functional! properties! makes! of! SrTiO3! one! of! the! basis! for! the! future! advance!of!oxide!electronic!applications.! ! The!purpose!of!this!lecture!is!to!provide!an!insightful!introduction!to!the!electronic!structure!of!SrTiO3,! starting!from!the!most!basic!concepts!linking!its!symmetry!properties!to!the!crystal!structure.!The!effect! on! the! electronic! properties! of! the! deviations! of! the! perfect! bulk! crystal,! either! by! surface! intrinsic! effects!or!by!extrinsic!doping!with!foreign!atoms!will!be!discussed.!!The!main!mechanisms!of!electronic! transport! and!optical! properties!–e.g.,!electron!scattering!mechanisms!and! photoluminescence–will!be! described!in!the!framework!of!point"like!defects!–vacancies!or!substitutional!ions!in!the!lattice!–!.!!!An! overview! of! experimental! approaches! will! be! presented! allowing! unraveling! the! specificities! of! the! electronic! band! structure! at! surfaces! (e.g.,! via! photoemission! spectroscopy)! and! at! the! bulk! of! the! crystals! (e.g.,! via! strain"dependence! of! the! electronic! transport).! The! deep! fundamental! knowledge! of! SrTiO3! provided! by! all! these! tools! afford! the! basic! ground! for! the! understanding! of! the! intriguing! electronic!properties!of!SrTiO3!heterointerfaces!involving!other!perovskites!such!as!LaAlO3!or!LaTiO3.! ! Recommended!bibliography:! (1)!T.!Wolfram!&!S.!Ellialtioglu,!Electronic!and!Optical!Properties!of!d"Band!PerovskitesMagneto"Optics,! Cambridge!University!Press,!2006;!(2)!S.!Maekawa,!T.!Tohyama,!S.!E.!Barnes,!S.!Ishihara,!W.!Koshibae,!G.! Khaliullin,!Physics!of!Transition!Metal!Oxides!(Springer!Series!in!Solid"State!Sciences),!2004.! ! ! !!

!

Rare!earth"nickelates" !

Marjana!Ležai"! ! Peter!Grünberg!Institut,!Forschungszentrum!Jülich,!D#52425!Jülich,!Germany!! ! ! ! Rare#earth! nickelates! RNiO3! (where! R! is! a! rare! earth! from! Pr! to! Lu)! display! a! sharp! metal! to! insulator! transition!at!the!temperature!TMI!which!strongly!depends!on!the!size!of!the!particular!rare#earth!cation.! Furthermore,!a!transition!from!a!paramagnetic!phase!to!an!antiferromagnetic!phase!occurrs!at!the!Néel! temperature! TN! that! is! lower! or! equal! to! the! metal#insulator! transition! temperature.! The! low! temperature! insulating! state! is! characterized! by! the! presence! of! two! nonequivalent! Ni! sites! with! different!oxygen!surroundings,!possibly!accompanied!by!charge!disproportionation!effects.!The!richness! of!the!physics!of!these!compounds!allows!for!their!tunability!by!e.g.!strain,!doping!or!external!fields!and! offers!potential!for!novel!oxide!electronics!devices.!In!this!lecture!we!will!discuss!rare#earth!nickelates! with!a!special!emphasis!on!their!properties!in!thin!films.!

!

Oxide!Interfaces!(theory)! !

Rossitza!Pentcheva! ! Ludwig!Maximilians!University!Munich,!Germany!! ! ! ! Oxide!interfaces!have!attracted!continued!interest!over!the!past!years!due!to!the!novel!properties!and! functionalities! they! exhibit! that! are! not! available! in! the! bulk! compounds.! In! this! lecture! I! will! give! an! overview!on!the!progress!in!understanding!these!novel!phenomena!based!on!first!principles!calculations.! After! a! brief! introduction! of! the! methods,! I! will! address! the! concepts! of! polarity! and! mechanisms! of! compensation!and!their!implications!for!the!stabilization!of!novel!electronic!and!magnetic!states!at!oxide! interfaces.! Further! topics! include! the! effect! of! strain,! finite! size! and! confinement! effects! in! triggering! electronic! transitions! and! orbital! reconstruction! in! these! systems.! Examples! will! include! perovskite! interfaces!such!as!the!LaAlO3/SrTiO3!system!(see!related!experimental!lecture!by!M.!Triscone),!nickelates! as!well!as!other!interfaces!based!on!spinel!or!corundum!lattices.!! ! ! ! !!

Interfacial Effects in Novel Oxide Heterostructures Jean-Marc Triscone DPMC, University of Geneva, 24 quai E.-Ansermet, CH-1211 Geneva 4, Switzerland Oxide materials display within the same family of compounds a variety of exciting electronic properties ranging from ferroelectricity to ferromagnetism and superconductivity. These systems are often characterized by strong electronic correlations, complex phase diagrams and competing ground states. This competition makes these materials very sensitive to external parameters such as pressure or magnetic field. An interface, which naturally breaks inversion symmetry, is a major perturbation and one may thus expect that electronic systems with unusual properties can be generated at oxide interfaces [1,2]. A striking example is the interface between LaAlO3 and SrTiO3, two good band insulators, which was found in 2004 to be conducting [3], and, in some doping range, superconducting with a maximum critical temperature of about 200 mK [4]. In this lecture, I will motivate the search for novel properties at oxide interfaces. I will first mention some results obtained at oxide surfaces before to focus on the LaAlO3/SrTiO3 system. In this latter interfacial system, the thickness of the electron gas is found to be a few nanometers at low temperatures. This electron gas with low electronic density, typically 5 1013 electrons/cm2, and naturally sandwiched between two insulators is ideal for performing electric field effect experiments allowing the carrier density to be tuned. I will discuss the origin of the electron gas [5]; superconductivity [4,6]; field effect experiments and the phase diagram of the system [6]; the role of spin orbit [7,8]; and the physics of high mobility samples that display Shubnikov de Haas oscillations [9]. I will also talk about nickelate-based heterostructures that may be a way to realize new superconductors and that are attracting a lot of attention [10]. In such structures, charge transfer and charge ordering phenomena may induce novel properties as recently observed in (111) LaNiO3/LaMnO3 (LNO/LMO) superlattices where evidences for exchange bias were found. In this particular case, it indicates that a magnetic order is induced within the paramagnetic LNO material when embedded between ferromagnetic LMO layers [11]. [1] J. Mannhart and D. Schlom, Science 327, 1607 (2010). [2] P. Zubko, S. Gariglio, M. Gabay, P. Ghosez, and J.-M. Triscone, Annual Review : Condensed Matter Physics 2, 141 (2011). [3] A. Ohtomo, H. Y. Hwang, Nature 427, 423 (2004). [4] N. Reyren, S. Thiel, A. D. Caviglia, L. Fitting Kourkoutis, G. Hammerl, C. Richter, C. W. Schneider, T. Kopp, A.-S. Ruetschi, D. Jaccard, M. Gabay, D. A. Muller, J.-M. Triscone and J. Mannhart, Science 317, 1196 (2007). [5] M.L. Reinle-Schmitt, C. Cancellieri, D. Li, D. Fontaine, S. Gariglio, M. Medarde, E. Pomjakushina, C.W. Schneider, Ph. Ghosez, J.-M. Triscone, and P.R. Willmott, Nature Communications, 3, 932 (2012). [6] A. Caviglia, S. Gariglio, N. Reyren, D. Jaccard, T. Schneider, M. Gabay, S. Thiel, G. Hammerl, J. Mannhart, and J.-M. Triscone, Nature 456, 624 (2008). [7] A.D. Caviglia, M. Gabay, S. Gariglio, N. Reyren, C. Cancellieri, and J.-M. Triscone, Physical Review 104, 126803 (2010). [8] A. Fête, S. Gariglio, A. D. Caviglia, M. Gabay, J.-M. Triscone, Physical Review B (RC) 86, 201105 (2012). [9] A.D. Caviglia, S. Gariglio, C. Cancellieri, B. Sacépé, A.Fête, N. Reyren, M. Gabay, A.F. Morpurgo, J.M. Triscone, Physical Review Letters 105, 236802 (2010). [10] J. Chaloupka, G. Khaliullin, Physical Review Letters 100, 016404 (2008). [11] M. Gibert, P. Zubko, R. Scherwitzl, J. Iniguez, and J.-M. Triscone, Nature Materials 11, 195 (2012)

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Polarized!Light!for!Spectroscopy!and!Domain!Imaging! Gervasi!Herranz! Institute!of!Materials!Science!of!Barcelona!ICMAB"CSIC! Campus!de!la!UAB,!08193!Bellaterra,!Catalonia,!Spain! Email:[email protected]! Phone:!+34!93!580!18!53!(ext.!357)! ! ! As!light!is!transmitted!through!or!reflected!from!a!material,!its!polarization!state!undergoes!changes!that! can! be! traced! back! to! the! materials! properties.! In! particular,! light"matter! interaction! results! in! phenomena!–such!as!birefringence!or!dichroism–!that!emerge!when!some!kind!of!symmetry!is!broken.! An!example!is!given!by!the!anisotropic!crystals!in!which!the!refractive!index!depends!on!the!propagation! direction! of! light! with! respect! to! the! crystal! axes.! This! gives! way! to! birefringence! resulting! from! the! rotation! of! the! plane! of! polarization! with! respect! to! the! initial! incoming! light.! Alternatively,! dichroism! appears! when! light! becomes! elliptically! polarized! when! the! absorption! in! the! material! is! changed! for! different!polarized!states.! ! Interestingly,!mechanisms!other!than!crystal!anisotropy!may!also!generate!birefringence!or!dichroism.!In! piezoelectric!systems,!the!application!of!electric!fields!induces!strain!that,!in!turn,!leads!to!birefringence! in!linearly!polarized!light!because!the!material!is!stretched!and/or!bent,!resulting!in!deformations!that! induce! extra! anisotropy! along! specific! orientations.! In! addition,! ferroelectric! materials! also! exhibit! birefringence! induced! by! the! electro"optic! effect! because! of! the! lack! of! space! inversion! symmetry,! resulting!in!birefringence!that!is!linear!with!electric!field.!Finally,!for!magnetic!materials,!the!presence!of! a! net! magnetization! induces! birefringence! and! dichroism! when! circularly! polarized! light! is! transmitted! through! the! magnetic! medium! (Faraday! rotation/ellipticity)! or! reflected! from! a! magnetic! surface! (Kerr! rotation/ellipticity).! ! Thus,! whereas! circular! magnetic! birefringence/dichroism! is! a! well! known! method! for! magnetic! characterization,!linear!birefringence!is!a!suitable!probe!for!piezoelectric/ferroelectric!characterization.! This!makes!the!optical!characterization!based!on!optical!polarization!contrast!a!powerful!tool!to!analyze! multiferroic! systems.! The! lecture! will! give! an! overview! on! the! fundamentals! and! basic! concepts! of! birefringence!and!dichroism.!Experimental!approaches!will!be!presented!for!the!optical!characterization! and! domain! imaging! of! multiferroic! systems! based! in! ferromagnetic/ferroelectric! bilayers.! Combined! with! confocal! microscopy,! optical! polarization! contrast! via! electric"! or! magnetic"driven! birefringence/dichroism!allows!ferroelectric!and!domain!imaging!with!lateral!spatial!resolution!down!to! a!few!hundreds!of!nanometer.!At!the!same!time,!optical!measurements!combined!with!in"situ!applied! electric! and/or! magnetic! fields! will! be! presented,! allowing! the! dynamic! evolution! of! domains! with! external!fields.! ! Recommended!bibliography:! Magneto"Optics:!A.!Zvezdin!and!V.!Kotov,!Modern!Magnetooptics!and!Magnetooptical,!Materials!Taylor! &!Francis,!London,!1997;!J.!Ferré!and!G.A.!Gehring!Linear!optical!birefringence!of!magnetic!crystals!Rep.! Prog.! Phys.! 47! 513! (1984);! Robert! E.! Newnham,! Properties! of! Materials:! Anisotropy,! Symmetry,! Structure,!Oxford!University!Press,!2005.! !!

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Point!defects!in!semiconducting!oxides!! ! Andreas!Klein! ! Technische!Universität!Darmstadt,!Institute!of!Materials!Science,!Surface!Science!Division,! Petersenstrasse!32,!64287!Darmstadt,!Germany!! ! ! ! Point!defects!are!abundant!in!ionic!materials!and!can!significantly!influence!their!functional!properties.! Depending!on!ionicity,!Schottky!and!Frenkel!defect!pairs,!vacancies!and!interstitials,!and!antisites!are!the! dominant!defect!species!in!halides,!chalcogenides!and!pnictides,!respectively.!For!materials!having!not! too!large!energy!gaps,!also!free!electrons!and!holes!have!to!be!taken!into!account.!The!defect!concen" trations!in!equilibrium!are!determined!by!the!defect!formation!enthalpies!and!charge!neutrality.!There! are! two! distinct! approaches! treating! defect! properties! in! semiconducting! oxides.! Defect! chemistry! considers!defect!reactions!and!obtains!defect!concentrations!via!mass!action!laws.!This!leads!to!a!set!of! non"linear!equations,!which!is!typically!solved!within!the!Brouwer!approximation,!which!considers!only! the!dominant!defect!reaction!in!dependence!on!oxygen!partial!pressure.!Basic!dependencies!of!defect! concentrations!as!a!function!of!oxygen!partial!pressure!and!doping!can!be!derived!using!this!approach.! The!second!approach!emerged!from!ab"initio!calculations!of!defect!formation!energies.!In!this!approach! each! defect! is! treated! as! an! independent!entity,! which! formation!energy! is!a! function! of! the! chemical! potential! of! the! species.! In! oxides,! the! chemical! potentials! are! directly! related! to! the! oxygen! partial! pressure.!For!charged!defects,!the!chemical!potential!of!electrons!contributes!to!the!formation!enthalpy.! In!other!words,!the!defect!formation!enthalpy!of!a!charged!defect!depends!on!the!Fermi!energy.!Using! this!approach,!the!phenomenon!of!self"compensation!emerges!as!a!natural!consequence!of!the!defect! properties.! Self"compensation! limits! the! concentration! of! free! carriers,! which! determines! whether! a! material!with!an!energy!gap!can!be!made!electronically!conducting!by!doping!(either!n"type,!p"type,!or! ambipolar)! or! will! be! an! insulator.! Moreover,! self"compensation! defines! a! region! of! thermodynamic! stability!of!materials.!! ! The!lecture!will!introduce!the!basic!properties!of!defects!in!semiconducting!oxides!and!explain!the!two! different!approaches!for!describing!defect!properties.!The!concepts!will!be!exemplified!using!transparent! conducting!oxides!and!perovskites.!! !

!

Conductive!tip"atomic"force"microscopy" !

Vincent!Garcia! ! Unité!Mixte!de!Physique!CNRS/Thales,!Palaiseau,!France! ! ! ! Conductive"tip! atomic! force! microscopy! (CT"AFM)! is! a! powerful! tool! to! investigate! the! electronic! transport! properties! of! thin! films! and! heterostructures! at! the! nanoscale.! In! the! basic! operation! of! CT" AFM,! the! conductive! probe! is! scanning! in! contact! mode! across! the! sample,! while! a! DC! bias! is! applied! between!the!sample!and!the!tip.!The!resulting!current!is!measured!using!a!current!amplifier,!mapping! the!local!resistance!of!the!sample!at!the!nanoscale.!Various!applications!of!CT"AFM!will!be!illustrated!on! specific! examples! with! oxide! materials! including! the! observation! of! parasitic! phases! in! thin! films,! the! characterization!of!tunnel!barriers,!the!LAO/STO!interface,!the!conduction!at!ferroelectric!domain!walls…! In!this!lecture,!I!will!try!to!untangle!some!of!the!surprises!encountered!in!everyday!life!of!oxide!research! when!having!a!look!at!“real”!samples.!

!

Basics!of!(ferro")!Elasticity! !

Ekhard!Salje! ! University!of!Cambridge,!Department!of!Earth!Sciences!Downing!Street,!Cambridge!CB2!3EQ!! ! ! ! Intrinsic! elastic! softening! during! phase! transitions! is! well! understood:! this! softening! is! related! to! the! coupling! between! the! order"parameter! susceptibility! and! strain! variables.! Such! intrinsic! effects! can! be! observed! at! high! frequencies! (e.g.! Brillouin! scattering)! or! in! samples! without! any! microstructure.! A! complete! review! of! intrinsic! elastic! instabilities! is! given! in! (1).! Current! research! focuses! on! the! much! more! complex! question! of! extrinsic! elastic! softening.! These! softening! effects! relate! to! relaxations! of! microstructures! and! mirror! the! properties! of! mircostructural! boundaries.! The! key! microstructure! in! elasticity!is!twinning;!mobile!twin!boundaries!are!the!hallmark!of!ferroelasticity!and!any!elastic!hysteresis! behaviour.!Their!mobility!determines!the!collapse!of!the!elastic!moduli!at!a!ferroelastic!phase!transition.! The!experimental! determination! of!effective! moduli! uses!today! mainly! DMA! (2)! and! RUS! (3)! methods.! Functional! twin! boundaries! can! be! excited! by! conjugated! fields! which! are! neither! strain! nor! stress.! A! typical!example!is!CaTiO3!which!contains!polar!twin!boundaries!(while!the!matrix!is!strictly!non"polar).!In! this!case! we!apply!electric! fields!to!generate!elastic!waves! (RPS=!resonant!piezoelectric!spectroscopy).! Such!‘piezoelectric!coupling’!in!the!twin!boundary!is!symmetry!forbidden!in!the!bulk!so!that!excitations! relate! exclusively! to! mobile! microstructures.! Recent! results! on! SrTiO3! show! clear! indications! that! wall! polarity! in! non"polar! crystals! occur! at! temperatures! well! below! the! ferroelastic! phase! transition.! The! elastic!wall!instabilities!are!simulated!in!large"scale!MD!computer!models,!the!results!of!such!models!will! be!presented!(4).! ! (1)Carpenter,! MA;! Salje,! EKH! (1998)! Elastic! anomalies! in! minerals! due! to! structural! phase! transitions! EUROPEAN!JOURNAL!OF!MINERALOGY!10,693.! (2)! Salje! EKH,! Schranz! W! (2011)! Low! amplitude,! low! frequency! elastic! measurements! using! Dynamic! Mechanical!Analyzer!(DMA)!spectroscopy!ZEITSCHRIFT!FUR!KRISTALLOGRAPHIE!!226,!1.! (3)! Salje! EKH,! Carpenter! MA,! Nataf! GF! et! al! (2013)! Elastic! excitations! in! BaTiO3! single! crystals! and! ceramics:! Mobile! domain! boundaries! and! polar! nanoregions! observed! by! resonant! ultrasonic! spectroscopy!PHYSICAL!REVIEW!B!87,!014106.! (4)!Salje!EKH,!Ding!X!et!al.!2011!Thermally!activated!avalanches:!Jamming!and!the!progression!of!needle! domains!PHYSICAL!REVIEW!B!83,!104109.!!!! ! ! ! !!

!

Flexoelectric!Spectroscopy! !

J.!F.!Scott! ! Cavendish!Laboratory,!Dept.!Physics! Cambridge!University! !! ! ! ! Flexoelectricity!is!the!production!of!a!voltage!via!application!of!an!inhomogeneous!stress!or!its!converse! effect.!Discovered!by!Kagan!in!1964,!it!was!subsequently!studied!in!some!detail!by!Scott!(March!1968)! and! Biursian!(October! 1968),! and!has! been! reviewed! by! Tagantsev! (1986)! and! very! recently! by! Zubko,! Catalan,! and! Tagantsev! (2013).! In! bulk! ceramics! or! single! crystals! it! is! usually! a! small! effect,! but! since! inhomogeneous!strain!usually!varies!as!reciprocal!thickness,!it!can!be!very!large!in!thin!films.!It!may!have! commercial!application!in!push"button!on"off!switches,!for!example.!In!the!present!lecture!I!emphasize!a! relatively! unexplored! area! of! study! "! flexoelectric! spectroscopy,! whereby! "silent"! vibrational! modes! (neither!Raman"!nor!infrared"active)!become!strong!under!inhomogeneous!stress,!with!details!given!for! tetragonal! scheelite! structures!epitomized!by! CaWO4,! and! for!pseudo"cubic! structures! such! as! SrTiO3.! This!new!flexoelectric!spectroscopy!permits!quantitative!study!of!flexoelectricity!in!very!thin!films,!nano" devices,!or!objects!in!inaccessible!or!hazardous!environments.! ! ! ! !!

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Physics!of!High!Tc!Superconductors!!! ! Jacobo!Santamaría!! ! ! GFMC,!Departamento!de!Física!Aplicada!III,!Universidad!Complutense!de!Madrid,!28040!Madrid,!Spain!!! !! ! ! ! More!than!twenty!years!after!the!discovery!of!the!High!Tc!Superconductivity!there!are!still!many!open! questions!regarding!the!origin!and!mechanism!of!the!phenomenon.!In!particular!the!so!called!pseudo" gap!state!and!its!relation!to!the!superconductivity!or!the!intermediate!particle!in!the!pairing!interaction! are!subjects!of!intense!debate!in!the!literature.!In!the!mean!time,!on!the!other!hand,!quite!significant! process!has!been!achieved!in!the!understanding!of!the!vortex!matter!in!this!system,!which!has!been!key! to!advance!in!the!development!of!wires!and!tapes!to!the!level!of!making!applications!feasible.!!In!this! lecture!I!will!review!a!number!of!basic!problems!in!the!physics!of!the!cuprates!with!special!emphasis!on! the!description!of!the!pseudogap!state,!phase!separation!phenomena!and!the!importance!of!magnetic! excitations!in!the!reconstruction!of!the!Fermi!surface.!I!will!describe!the!basic!phenomenology!of!the!of! the!vortex!physics!in!the!High!Tc!superconductivity!focusing!on!pinning!and!their!!!mechanisms.!Finally!I! will!describe!recent!progress!in!experiments!of!tunnelling!phenomena!and!proximity!mechanisms!made! with!thin!films!which!have!been!of!significance!in!exploring!the!pairing!mechanism.! ! !

Domain wall transport: the key role of oxygen vacancies in ferroelectric domain wall conduction Patrycja Paruch DPMC-MaNEP, Université de Genève, Switzerland

In ferroelectric materials, regions with different orientation of electric polarization are separated by thin elastic interfaces known as domain walls. At domain walls, intrinsic effects such as the change/breaking of crystal symmetry or modification of the electronic structure, as well as extrinsic effects such as charge/defect segregation can lead to novel functional properties, quite different from those of their parent materials. The extreme localisation of such properties at the intrinsically nanoscale domain walls could make them potentially useful as active components in future miniaturized electronic devices [1]. It also poses a unique challenge for experimenters working to understand the mechanisms at the origin of the observed behaviour.

In this course, I will focus in particular on the recently discovered electric conductivity, shown first at domain walls in multiferroic BiFeO3 [2], and subsequently generalized to the simpler, canonical ferroelectric Pb(Zr,Ti)O3 [3], and multiple other systems [4]. I will disuss the multiple different microscopic mechanisms which have been proposed to explain the observed domain walls currents, and how these have been tested experimentally, differentiating between displacive and conductive contributions [5]. I will highlight the emerging consensus about the key role of oxygen vacancies and charged domain walls in this observed conduction [6], and compare the conductive behaviour to previously observed conductivity/resistivy enhancement in twin walls of doped ferroelastic materials [7]. 1. Bea et al, Nat. Mat. 8, 168 (2009); Salje, ChemPhysChem 11, 940 (2010); Catalan et al, Rev. Mod. Phys. 84, 119 (2012) 2. Seidel et al, Nat. Mat. 8, 229 (2009); Farokhipoor et al, PRL 107, 127601 (2011) 3. Guyonnet et al, Adv. Mat. 23, 5377 (2011) 4. Wu et al. PRL 108, 077203 (2012), Meier et al. Nat. Mat. 11, 284 (2012); Schröder et al. Adv. Fun. Mat. (2012) 5. Eliseev et al., PRB 83, 235313 (2011); Maksymovych et al., NanoLett. 8, 229 (2011) 6. Seidel et al., PRL. 105, 197603 (2010); Farokhipoor et al, JAP 112, 052003 (2012) 7. Aird et al, JPCM 10, 377 (1998); Bartels et al, JPCM 15, 957 (2003)

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Novel!phenomena!at!oxide!interfaces!! ! Jacobo!Santamaría!! ! ! GFMC,!Departamento!de!Física!Aplicada!III,!Universidad!Complutense!de!Madrid,!28040!Madrid,!Spain!!! !! ! ! ! The!discoveries!of!unexpected!properties!at!the!interfaces!between!complex!oxides!have!triggered!the! launch!of!a!novel!field!of!research!which!has!rapidly!expanded!in!recent!years.!!Modified!bonding!at!the! interface!may!be!at!the!bottom!of!the!appearance!of!interesting!novel!behaviours!not!appearing!in!the! bulk! constituents.! The! possibility! of! tailoring! the! electronic! structure! of! interfaces! has! driven! an! important!effort!towards!the!design!of!interfaces!with!specific!functionalities.!In!this!talk!I!will!focus!on! the!possibility!of!creating!novel!interfacial!magnetic!states!in!oxide!heterostructures.!They!originate!at! the! modification! of! the! orbital! occupancy! resulting! from! the! modified! bonding! at! the! interface.! I! will! discuss! the! effect! of! these! low! dimensional! magnetic! states! in! determining! the! macroscopic! magnetic! response!of!magnetic! tunnel! junctions.!In!particular,!I!will!discuss! the!possibility! of! reversible,! voltage" driven! magnetization! switching! of! a! manganite! layer! at! the! interface! with! a! (non! superconducting)! cuprate!in!the!absence!of!a!magnetic!field.!!Orbital!reconstruction!at!the!interface!yields!a!novel!form!of! magnetoelectric!coupling!between!interfacial!Mn!spins!and!localized!electron!states!in!the!CuO2!planes,! which!mediates!a!ferromagnetic!coupling!between!manganite!layers!sandwiching!the!cuprate!and!can!be! controlled! by! the! electric! field.! ! This! allows! switching! between! bistable! magnetization! states! (and! corresponding! ! spin"dependent! resistance! states! in! magnetic! tunnel! junctions)! in! the! absence! of! a! magnetic!field.! ! ! Work!done!in!collaboration!with!F.!A.!Cuellar1,!J.!Garcia"Barriocanal1,!D.!Arias1,!Z.!Sefrioui1,!C.!Leon1!,!N.! Nemes1,! ! M.! Bibes2,! and! A.! Barthélémy2,! M.! Garcia! Hernandez3,! Y.! H.! Liu4,! S.! G.! E.! te! Velthuis4,! M.! R.! Fitzsimmons5,!!M.!Varela6,!!S.!J.!Pennycook6! ! 1

GFMC,!Depto.!Física!Aplicada!III,!Universidad!Complutense!de!Madrid,!28040!Madrid,!Spain!! Unité!Mixte!de!Physique!CNRS/Thales,!Campus!de!Polytechnique,!1,!Avenue!A.!Fresnel,!91767!Palaiseau! (France)!and!Université!Paris"Sud,!91045!Orsay!(France)! 3 Instituto!de!Ciencia!de!Materiales!de!Madrid!(ICMM"CSIC).!28049!Cantoblanco.!Madrid.! 4 Materials!Science!Division,!Argonne!National!Laboratory,!Argonne,!Illinois!60439,!USA! 5! Los!Alamos!National!Laboratory,!Los!Alamos!NM!87545!USA! 6 Condensed!Matter!Sciences!Division,!Oak!Ridge!National!Laboratory,!Oak!Ridge,!Tennessee!37831"6031,! USA!! ! ! ! ! ! !! 2!

Oxide spintronics Manuel Bibes* Unité Mixte de Physique CNRS/Thales Palaiseau, France

Spintronics is a branch of electronics in which transport phenomena are dependent on the electron spin. Future spintronics devices will be built from elemental blocks allowing the electrical injection, propagation, manipulation and detection of spin-based information. Owing to their remarkable multi-functional and strongly correlated character, oxide materials already provide building blocks for charge-based devices such as ferroelectric field effect transistors (FETs), as well as for spin-based twoterminal devices such as magnetic tunnel junctions. In this lecture, I will first present results obtained on such oxide based tunnel junctions using half-metallic electrodes of e.g. manganese perovskites. Then, I will discuss the spin-filtering effect by which highly spin-polarized currents can be generated through tunneling across a thin ferromagnetic or ferrimagnetic insulator (EuO, BiMnO3, spinel ferrites), useable to obtain tunnel magnetoresistance. In a second part, I will review how oxide heterostructures can be designed to control magnetic and spin properties by an electric field, with a view towards spintronics architectures fully controlled by electrical means. Finally, I will discuss perspectives for spin injection and spin transport into non-magnetic oxide channels such as the LaAlO3-SrTiO3 interface system.

References : M. Bibes and A. Barthélémy, Oxide spintronics IEEE Trans. Electron. Dev. 54, 1003 (2007) (cf. ArXiv/ 0706.3015v1)

M. Bibes, J.E. Villegas and A. Barthélémy, Ultrathin oxide films and interfaces for electronics and spintronics Adv. Mater. 60, 5 (2011)

* [email protected]

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Wide Band-gap Oxide Semiconductors for Transparent Electronics Technologies! ! Dr.!D.!Lenoble! ! Centre!de!Recherche!Public!–!Gabriel!Lippmann,!Luxemburg! ! [email protected]! ! ! Transparent! Conducting! Oxides! (TCOs)! are! wide! band"gap! semiconductors! that! exhibit! both! (visible)! transparency!and!electronic!conductivity!simultaneously.!They!are!mainly!used!in!displays,!photovoltaics,! low"emissivity! windows,! flexible! electronics! as! transparent! contacts.! New! needs,! beyond! the! combination! of! conductivity! and! transparency,! that! include! work! function! tuning,! morphology,! processing!and!patterning!requirements,!long!term!stability,!lower!cost!and!elemental!abundance/green! materials,! have! emerged! over! the! past! decade! to! push! forward! the! manufacturing! of! transparent! transistor!with!higher!performance!and!true!oxide!based!p/n!junctions!to!realize!active!devices.!This!has! stimulated,! in! the! past! decade,! a! strong! resurgence! of! research! in! the! field! of! transparent! conductive! oxides.!! ! This!lecture!reviews!the!explosion!of!the!field!of!TCOs!over!the!past!10!years!that!includes!a!vast!number! of!n"type!materials!and!the!emerging!investigation!of!new!p"type!materials.!After!introducing!TCOs,!their! properties! and! their! historical! development,! the! emergent! materials! requirements! are! presented! into! their!technological!context.!The!key!properties!of!TCOs!are!discussed!based!on!their!electronic!structures! and! the! Moss"Burstein! shift! is! introduced.! The! theoretical! basis! to! apprehend! the! various! transport! mechanisms,!including!polarons,!is!detailled!and!the!influence!of!critical!parameters!such!as!carrier!type,! mobility,!scattering!mechanisms!in!multinary!oxides!is!discussed.!Because!of!its!important!applications!in! the! field! of! transparent! contacts! and! active! optoelectronics! devices,! ZnO! is! thoroughly! detailed! to! introduce! the! physics! and! the! theoretical! framework! underlying! the! complementary! doping! of! transparent! oxide! semiconductors! (TOS).! This! fundamental! background! provides! the! basis! for! the! discovery!of!new!high!performance!transparent!conducting!materials!to!elaborate!active!devices!that!are! fully!based!on!TCO/TOS!materials.!A!particular!focus!on!ternary!and!multinary!oxides!is!thus!presented!to! provide! the! relevant! insights! linking! the! crystal/defect! structures! of! these! materials! with! their! key! properties.!In!last,!the!paradigm!of!transparent!amorphous!oxide!semiconductors!(TAOS)!is!introduced! to!appraise!the!unique!features!of!TAOS"TFTs!that!are!used!for!novel!display!structure.!! !

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Solar!cells!! ! Andreas!Klein! ! Technische!Universität!Darmstadt,!Institute!of!Materials!Science,!Surface!Science!Division,! Petersenstrasse!32,!64287!Darmstadt,!Germany!! ! ! ! In! the! last! ten! years,! solar! cells! became! a! significant! technology! for! renewable! electricity! generation.! Today,!most!solar!cells!are!made!from!p/n!homojunction!diodes!of!crystalline!Si.!Due!to!its!indirect!band! gap,!Si!solar!cells!have!to!be!made!with!200!–!300!µm!thick!wafers!in!order!to!fully!absorb!the!accessible! portion!of!the!solar!spectrum.!Due!to!the!large!cell!thickness,!a!high!minority!carrier!diffusion!length!is! required!for!high!efficiencies!of!up!to!25%.!This!can!only!be!achieved!with!very!pure!material,!generating! high! production! costs.! Thin! film! solar! cells! are! an! alternative! technology! with! huge! potential! for! reduction!of!production!costs.!Available!technologies!are!based!on!p/n"heterodiodes!with!Cu(In,Ga)Se2! or! CdTe! as! absorber! materials! or! on! multijunction! p"i"n! diodes! made! with! nanocrystalline! and! amorphous!silicon.!Thin!film!solar!cells!are!deposited!on!square!meter!sized!glass!substrates!and!have! reached! record! efficiencies! above! 20%.! Dye! sensitized! and! organic! solar! cells! have! been! studied! intensively!but!not!reached!maturity!for!large!scale!manufacturing.!! ! The!lecture!will!describe!the!basic!physics!and!parameters!of!solar!cells!including!the!elementary!steps!of! carrier! generation,! separation,! transport,! and! recombination.! In! addition,! the! different! solar! cell! technologies! will! be! introduced.! Aspects! of! preparation,! materials,! and! interface! related! issues! will! be! discussed.!!!!!! !

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Ferroelectric!photovoltaics! !

Marin!Alexe! ! Max!Planck!Institute!of!Microstructure!Physics,!Halle,!Germany!and! University!of!Warwick,!Coventry,!UK!!! ! ! ! In! the! recent! past,! the! entire! field! of! photo"ferroelectrics! has! been! revitalized! by! the! reports! of! photovoltaic!(PV)!effect!in!BiFeO3!(BFO).!!Unlike!traditional!semiconductors!the!open!circuit!voltages!in! non"centrosymmetric!materials!such!as!BFO!are!not!limited!by!band!gap,!they!can!exceed!the!band!gap! of!the!material!by!orders!of!magnitude.!The!microscopic!origins!of!this!effect!are!still!under!debate.!For! instance! initial! investigations! on! BFO! films! assumed! that! the! PV! effect! in! BFO! is! primarily! due! to! the! presence! of! a! potential! step! at! the! domain! wall! which! enables! a! more! efficient! separation! of! charge! carriers.!However,!in!our!recent!work!it!was!observed!that!the!generation!and!recombination!of!photo" generated! non"equilibrium! carriers! in! a! BFO! single! crystal! are! primarily! affected! by! the! presence! of! shallow!energy!levels!and!the!domain!walls!might!not!playing!a!major!in!the!corresponding!PV!effect,!as! initially!proposed.!! This! lecture!will! address!fundamentals!of!photo"ferroelectrics! and!anomalous!bulk! photovoltaic!effect.! Besides! of! that! newly! characterization! methods! based! on! local! photoelectric! measurement! such! as! photo"induced! transient! spectroscopy! (PITS)! which! bring! valuable! data! regarding! generation! and! recombination! of! the! photo"excited! carriers! will! be! tackled.! We! will! also! discuss! complementary! characterization!methods!such!as!thermally!stimulated!current!and!variable!temperature!PV!effect!and! show!that!these!can!provide!information!on!details!regarding!the!electronic!structure!of!material!under! investigation,!respectively!shallow!or!deep!levels!in!the!band!gap,!which!may!affect!the!dark!and!photo" conduction!mechanism.! ! ! ! !!

What can we learn from electron spectroscopies with new light sources? Olof Karis Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden

The progress of materials science depends critically on the access to advanced characterization methods. During the last decades there has been an almost revolutionary development of modern X-ray-based tools. Electron spectroscopies are among the most important techniques for the advancement of materials science. Photoelectron spectroscopy, and related techniques like angular resolved photoelectron spectroscopy (ARPES), is evolving parallel to the development of a new generation of light sources like synchrotron radiation (SR) facilities and in in-house high harmonic generation (HHG) XUV/Xray sources. Today we have instruments that allow electron spectroscopy to move into new domains of time, spatial, energy and angular resolution. Current state of the art instruments provide energy resolution down to the micro-eV range with a simultaneous increase of the transmission of almost three orders of magnitude, compared to the earlier instruments allowing almost real-time studies of modifications of the electronic structure. In my presentation I will outline the governing principles for photoelectron spectroscopy and discuss some experimental aspects. I will provide examples of both didactical character and state-of-the-art to illustrate what is achievable today with modern instrumentation. In particular I will show how photoelectron spectroscopy performed with hard x-rays can be particularly valuable as the muchincreased mean free path of the emitted electron allow for studies of true bulk properties and buried interfaces. I will also show recent results that obtained with modern ARPES spectrometers relying on time-of-flight for energy analysis rather than a dispersive component.

X-ray absorption spectroscopy and magneto-optical techniques within the soft x-ray region S. Valencia Helmholtz-Zentrum-Berlin

In 1845, Michael Faraday probed that light could be magnetically affected. This was the first observation of a magneto-optical effect, i.e. the state of light was modified after travelling through a magnetized material. Nowadays this and other magneto-optical effects are commonly used for the characterization of magnetic materials as predicted by Faraday himself. The advent of synchrotron radiation sources allowed the transfer of these techniques, mostly used within the visible range, to the soft x-ray range (200-2000 eV) where among others the 2p->3d transitions of 3d transition metals are accessible. This opened up the possibility for a magnetic characterization of thin films, multilayers and buried interfaces in an element selective way. Within this talk we will describe the main achievements which led to the use of X-ray absorption spectroscopy and magneto-optical techniques within the soft xray region. The potential of these techniques for the qualitative and quantitative characterization of magnetic thin films will be shown by describing some recent results. In particular we will show how to extract chemical, magnetic and orbital information by means of X-ray absorption spectroscopy (XAS), X-ray magnetic circular dichroism (XMCD) and X-ray linear dichroism (XLD).

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X-ray Photoelectron emission microscopy (X-PEEM) S. Valencia Helmholtz-Zentrum-Berlin

This talk is a continuation of the talk “X-ray absorption spectroscopy and magnetooptical techniques within the soft x-ray region”.

Here we will show how the combination of X-ray absorption spectroscopy and magneto-optical techniques with the microscopy capabilities of photoelectron emission microscopy (PEEM) allows for a 2D space resolved magnetic and element selective characterization of buried thin films and nanostructures. After briefly describing the different parts of a PEEM microscope we will see different examples showing how X-PEEM can be used for surface and bulk characterization, depth dependent studies and static and dynamic measurements (with picosecond resolution) of chemical and magnetic properties. Finally we will show recent X-PEEM results on the investigation of the magnetic properties of individual nanocubes being 18 nm in lateral size.

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Inside!Nature!Materials! !

Andrea!Taroni! ! Nature!Publishing!Group,!4!Crinan!Street,!London,!N1!9XW,!UK.! ! ! ! Since! its! launch! in! 1869,! Nature! has! seen! its! mission! as! two"fold:! facilitating! the! prompt! communication! of! the! most! important! scientific! developments! to! the! relevant! research! communities,! while! at! the! same! time! fostering! a! greater! appreciation! of! these! great! works! of! science! amongst! the! wider!public.!Although!the!publishing!landscape!for!scientific!research!is!currently!undergoing!a!period!of! unprecedented!change,!these!core!principles!remain!largely!unchanged.!In!this!talk,!I!will!endeavour!to! shed!light!on!how!Nature!editors!–!in!particular!those!based!at!Nature!Materials!–!apply!these!principles! in! practice,! and! so! determine! which! few! of! the! many! excellent! research! submissions! that! we! receive! make!it!through!to!publication.! !

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Mössbauer!spectrometry! ! J.!Juraszek! ! Groupe!de!Physique!des!Matériaux,!UMR!6634!CNRS!–!Université!et!INSA!de!Rouen,!! Avenue!de!l’Université,!BP12,!76801,!Saint!Etienne!du!Rouvray!cedex,!France! ! ! ! Mössbauer!spectrometry!is!based!on!the!recoilless!nuclear!resonance!fluorescence!of!gamma!radiation! discovered! by! Rudolf! Mössbauer! during! his! PhD! thesis! in! 1958! [1].! The! so! called! “Mossbauer! effect”! opens!the!way!to!a!new!spectroscopic!technique!for!the!non!destructive!characterization!of!materials!by! providing!element"specific!information!on!surrounding!electronic!states!and!magnetism.!It!has!initiated! overwhelming!research!activities!in!nearly!all!fields!of!science!and!recognition!in!the!form!of!Nobel!prize! was!awarded!to!Rudolf!Mössbauer!a!few!years!later!in!1961.!The!high!resolution!of!!Mössbauer!effect! made! it! possible! to! resolve! the! hyperfine! interactions! consisting! in! interactions! between! a! nuclear! (moment)! properties! and! an! appropriate! electronic! or! atomic! properties.! The! hyperfine! coupling! mechanisms! are! of! great! significance! yielding! information! regarding! electron"! and! spin"density! distributions.!Three!types!of!hyperfine!interactions!between!nuclear!moments!and!electrons!penetrating! the!nucleus!that!can!be!observed!in!a!Mössbauer!spectrum:!the!electric!monopole!interaction!resulting! in!the!isomer!shift,!the!electric!quadrupole!interaction!causing!the!quadrupole!splitting!and!the!magnetic! dipole!interaction!giving!rise!to!magnetic!splitting!of!degenerate!nuclear!levels.!! ! In! this! tutorial! lecture,! we! will! first! introduce! some! general! aspects! of! hyperfine! interactions! and! their!consequences!on!the!shape!of!a!Mössbauer!spectrum.!We!will!then!focus!on!common!applications! of! 57Fe! Mössbauer! spectrometry! for! characterizing! magnetic! compounds.! This! will! include! the! determination!of!magnetic!transition!temperatures,!phase!analysis!and!site!distribution!studies.!! The!conversion!electron!Mössbauer!spectrometry!(CEMS)!technique!allowing!analysis!of!thin!magnetic! films,! such! as! iron! oxides! for! spintronics! applications,! will! be!described.! Using! this! technique,! not! only! the! magnitude! of! the! hyperfine! field! (roughly! proportional! to! the! Fe! magnetic! moment)! but! also! its! orientation!with!respect!to!the!direction!of!the!incident!!"ray!can!be!obtained.!Moreover,!we!will!show! that!high!depth!selectivity!can!be!achieved!by!using!probe!layers!of!the!57Fe!Mössbauer!isotope,!inserted! during! specimen! preparation.! It! is! therefore! possible! to! probe! with! monolayer! resolution! the! spin! structure!in!a!specific!buried!region,!such!as!at!the!interface!between!two!different!layers.! Finally! we! will! show! how! the! use! of! synchrotron! radiation! (nuclear! resonance! scattering)! offers! new! features! and! enables! experiments! under! extreme! conditions! such! as! high! pressures,! very! high! or! very! low!temperatures,!and!strong!external!magnetic!fields.! ! ! [1]!R.L.!Mössbauer,!Recoiless!nuclear!resonance!absorption!of!!"radiation.!Science!137,!731–738!(1962).!

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Electric!field!effects!in!oxides! ! Javier!E.!Villegas1,!L.!Begon"Lours1,!A.!Crassous1,!H.!Yamada1,2,!M.!Marinova3,!P.!Altuntas1,!! Stéphane!Fusil1,4,!E.!!Jacquet1,!V.!Garcia1,!K.!Bouzehouane1,!Alexandre!Gloter3,!Manuel!Bibes1!&!Agnès! Barthélémy!1! !!! 1 Unité!Mixte!de!Physique!CNRS/Thales,!Palaiseau!and!Université!Paris!Sud,!Orsay,!France! 2 National!Institute!of!Advanced!Industrial!Science!and!Technology!(AIST),!Tsukuba,!Japan! 3 Laboratoire!de!Physique!des!Solides,!Université!Paris"Sud,!CNRS,!Orsay,!France! 4 Université!d’Evry"Val!d’Essonne,!Evry,!France! ! Complex!oxides!are!strongly!correlated!electrons!systems!in!which!slight!variations!of!the!charge!carrier! concentration! lead! to! dramatic! changes! of! the! physical! properties! [1].! In! addition! to! its! fundamental! interest,!this!characteristic!offers!significant!potential!for!novel!technological!applications,!as!it!expands! the!possibilities!of!the!electrostatic!tuning!of!the!carrier!concentration!(“field"effect!doping”)!from!the! simple! manipulation! of! charge! currents! –as! in! classical! field"effect! transistors–! to! the! control! of! functional!properties!such!as!magnetism!or!superconductivity![2,3].!! ! This!area!of!research!has!attracted!increasing!attention!during!the!last!years.!Significant!advances!have! been!made!in!the!control!of!physical!properties!via!field"effects,!via!new!approaches!such!as!the!use!of! liquid! electrolytes! [4"7]! and! ferroelectrics! [8"11]! as! gating! materials! !instead! of! simple! dielectrics.! We! will! discuss!the!advantages!of!these!types! of! gates,! which!include!the!possibility! to! attain!much!larger! carrier! modulations,! and! the! ability! to! obtain! non"volatile! reversible! field"effects.! We! will! describe! various!examples!in!which!strong!field"effects!are!achieved!in!oxides:!the!switching!of!superconductivity! [4"6,8,10],! the! modulation! of! the! metal"to"insulator! transition! [7]! and! conductivity! [11]! in! Mott! insulators,!or!the!modulation!of!magnetic!properties!in!manganites![9].! ! [1]!M.!Bibes,!J.!E.!Villegas!and!A.!Barthélémy,!Adv.!Phys.!60,!4!(2011)! [2]C.!H.!Ahn,!J.!M.!Triscone,!and!J.!Mannhart,!Nature!(London)!424,!1015!(2003).! [3]!C.!H.!Ahn!et!al.,!Rev.!Mod.!Phys.!78,!1185!(2006).! [4]!K.!Ueno,!et!al.,!Nat.!Mater.!7,!855!(2008)! [5]!A.!T.!Bollinger,!G.!Dubuis,!J.!Yoon,!D.!Pavuna,!J.!Misewich!&!I.!Bozovic,!Nature!472,!458!(2011)! [6]X.!Leng,!J.!Garcia"Barriocanal,!S.!Bose,!Y.!Lee,!and!A.!M.!Goldman,!Phys.!Rev.!Lett.!107,!027001!(2011)! [7]!M.!Nakano,!et!al.!!Nature!487,!459–62!(2012)! [7]!S.!Mathews,!R.!Ramesh,!T.!Venkatesan,!and!J.!Benedetto,!Science!276,!238!(1997).! [8]!K.!S.!Takahashi,!M.!Gabay,!D.!Jaccard,!K.!Shibuya,!T.!Ohnishi,!M.!Lippmaa,!and!J.!M.!Triscone,!Nature! (London)!441,!195!(2006).! [9]!C.!A.!F.!!Vaz!et!al.!!J.!Appl.!Phys.!109,!07D905!(2011).! [10]!A.Crassous,!R.!Bernard,!S.!Fusil,!K.!Bouzehouane,!D.!Le!Bourdais,!J.!Briatico,!M.!Bibes,!A.!Barthélémy,! and!J.!E.!Villegas,!Phys.!Rev.!Lett.!107,!247002!(2011);!J.!Appl.!Phys.!113,!024910!(2013).! [11]!H.!Yamada!et!al.,!submitted.! ! Work!supported!by!ANR!“SUPERHYBRIDS"II”!!

!

The!Spin!Torque!Lego! from!spin!torque!nano"devices!to!advanced!computing!architectures! !

Julie!Grollier! ! Unité!Mixte!de!Physique!CNRS/Thales,!Palaiseau,!France! [email protected]! ! ! ! Spin!torque!(ST)!has!upgraded!spintronic!devices!to!the!status!of!active!elements.!A!whole!class!of!new! devices,!based!on!the!combined!effects!of!ST!for!writing!and!GMR!or!TMR!for!reading!has!emerged.!The! second! generation! of! MRAMs,! based! on! spin! torque! writing:! the! ST"MRAM,! is! under! industrial! development!and!should!be!out!on!the!market!in!less!than!three!years.!! But! spin! torque!devices!are!far! from!being!limited!to!binary!memories.! I!will!rapidly!present!how!spin! torque! also! allows! implementing! non"linear! nano"oscillators,! spin"wave! emitters,! controlled! stochastic! devices!and!microwave!nano"detectors.!!What!is!extremely!interesting!is!that!all!these!functionalities!can! be!obtained!using!the!same!materials!and!the!exact!same!stack,!simply!by!changing!the!device!geometry! and! bias! conditions.! So! these! different! devices! can! be! seen! as! Lego! bricks,! each! brick! implementing! a! unique!functionality!at!the!nano"scale.!! During! this! talk,! I! will! show! how! spin! torque! can! be! engineered! to! build! new! bricks,! such! as! the! Spintronic! memristor,! an! artificial! magnetic! nano"synapse.! I! will! then! describe! how! these! spin! torque! Lego! bricks! could! be! assembled! to! build! novel! types! of! low! power,! high! performance! hardware! computing!circuits,!with!a!special!focus!on!neuromorphic!architectures.!! ! !

Resistive Switching Hermann Kohlstedt Nanoelektronik, Technische Fakultät der Christian-Albrechts-Universität zu Kiel, 24143 Kiel, Germany

Since a couple of years, the interest in memresistive devices has been renewed. Memristive devices are defined as variable resistors comprising a memory effect. Beside possible application in future high dense random access memories (RAMs), such devices are considered as artificial synapses and may be of relevance for neuromorphic circuits. Extensive studies have been carried out in the 60`s and 70`s of the last century. It is interesting to note that the main situation described by the authors is still valid today. That is, although resistive switching devices are attractive candidates for applications, the underlying physics and chemistry is only partly understood. This fact hinders so far a commercialization of memresistive devices. Resistive switching is a well known (i.e. easily obtainable but not really understood) phenomenon in metal-insulator(semiconductor)-metal (MIM) junctions observed in various material classes including amorphous -, micro-crystalline -, crystalline oxide insulators. The today investigated devices can be roughly categorized into valence change, electrochemical metallization, electronic, magnetoresistive, ferroelectric and nanomechanical, phase change (chalcogenides) and metal-insulator. A detailed understanding of the nature of the resistive switching effects is mandatory to be able to engineer useful memory devices. The talk compromises the discussion of various models including heat, ionic and/or electronic transport and mechanisms which involve an atomic rearrangement of the host insulator as well as the role of cooperative phenomena in case ferroelectric insulators are applied. Interface, volume and filament based devices will be compared. Finally I will comment on the rather different needs for memresistive devices for random access memories and for neuromorphic circuits.

!

Ferroelectric!tunnel!junctions! !

Vincent!Garcia! ! Unité!Mixte!de!Physique!CNRS/Thales,!Palaiseau,!France! ! ! ! After!being! conceptualized! in!the!early! 1970's,! ferroelectric! tunnel! junctions! (FTJs),! where! an! ultrathin! ferroelectric!film!is!sandwiched!between!two!electrodes,!have!remained!elusive!for!more!than!30!years.! In! 2009,! several! groups! including! ours! demonstrated! unambiguously! that! the! resistance! of! ultrathin! ferroelectric!films!depends!on!the!orientation!of!the!ferroelectric!polarization!combining!piezoresponse! force! microscopy! (PFM)! and! conductive"tip! atomic! force! microscopy! (CT"AFM).! This! contrast! in! resistance! is! called! tunnel! electroresistance! (TER)! and! can! reach! several! orders! of! magnitude! at! room! temperature.!This!breakthrough!opened!up!the!way!to!very!exciting!research!in!the!field!of!FTJs!over!the! past!few!years.!Solid"state!FTJs!show!a!large!TER!with!fast!low"energy!resistive!switching.!!The!dynamic! response!of!the!FTJs!is!directly!related!to!the!evolution!of!ferroelectric!domains!of!the!integrated!tunnel! barrier!imaged!by!PFM.!These!devices!are!emerging!as!an!alternative!to!other!resistive!memories!with! the! advantage! of! not! being! based! on! voltage"induced! migration! of! matter! at! the! nanoscale,! but! on! a! purely!electronic!mechanism.!Additionally,!ferroelectric!tunnel!junctions!with!ferromagnetic!electrodes! demonstrate! local,! large! and! non"volatile! control! of! carrier! spin! polarization! by! switching! ferroelectric! polarization.!Very!recent!experiments!have!shown!that!the!TER!can!be!enhanced!by!different!interfacial! approaches.! In! this! lecture,! I! will! give! a! rapid! overview! on! this! emerging! field! of! ferroelectric! tunnel! junctions.! ! ! !!

!

Memristors! !

Julie!Grollier! ! Unité!Mixte!de!Physique!CNRS/Thales,!Palaiseau,!France! [email protected]! ! ! ! Memristors!are!nanometer!size!non"volatile!tunable!resistances.!!The!resistance!state!of!these!devices! can!be!changed!by!varying!the!voltage!or!the!current!across!the!structure.!Depending!on!the!memristor! type,!the!resistive!switching!effects!can!be!due!to!several!different!physical!effects,!ranging!from!red"ox! to!charge"induced,!phase!change!or!purely!electronic!phenomena.! ! Practically,! due! to! the! possibility! to! easily! manipulate! their! resistance! state,! these! electronic! nano" devices! have! a! number! of! extremely! promising! applications,! such! as! digital! memories! (Resistive! Switching!RAMs),!switches!and!latches!for!advanced!logic!functions!etc.!In!addition,!since!their!resistance! can!in!general!be!tuned!over!several!orders!of!magnitude,!it!should!be!possible!to!stack!densely!these! components!in!large"scale!cross"bar!arrays.! ! One! of! the! most! fascinating! properties! of! memristors! is! that! they! intrinsically! behave! like! synapses,! which! could! be! a! key! to! the! future! development! of! hardware! Artificial! Neural! Networks! (ANNs),! and! revolutionize!non"conventional!neuromorphic!computing.!! ! This!talk!will!be!a!review!of!the!state!of!the!art!of!memristor!devices!and!their!applications,!with!a!special! focus!on!their!implementation!as!artificial!synapses!for!on"chip!neural!networks.!! ! ! !

Abstracts of posters

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WŽƐƚĞƌƐ

Mössbauer spectroscopy as a probe of antiferromagnetic properties of BiFeO3 thin films A. Agbelele1*, D. Sando2, I.C. Infante3, C. Carrétéro2, J.-M. Le Breton1, B. Dkhil3, A. Barthélémy2, M. Bibes2 et J. Juraszek1 1

2

Groupe de Physique des Matériaux, Université de Rouen (FRANCE)

Unité Mixte de Physique CNRS / Thales, Palaiseau & Université Paris-Sud, Orsay (FRANCE) 3

Laboratoire SPMS, Ecole Centrale Paris, Châtenay-Malabry (FRANCE) *presenting author : [email protected]

Bismuth ferrite (BiFeO3)

is one of the few materials in which ferroelectric and

antiferromagnetic orders, coupled together, coexist up to very high critical temperatures [1]. This makes it interesting for new technological applications including spintronics, where its multifunctional character can be used to manipulate spin depending transport through the ferroelectricity. Bulk BiFeO3, with slightly distorted rhombohedral structure, has G-type antiferromagnetic with cycloidal modulation of the magnetic moments on a long period of 62.4 nm. This type of magnetic structure, difficult to study by conventional magnetic measurements, is accessible only by few nuclear techniques including

57

Fe Mössbauer

spectroscopy. In this work, we present Mössbauer measurements at different temperatures on a series of BFO thin layers of 70 nm thick enriched by isotope

57

Fe on different substrates spanning a

strain range from -4.8 % (compressive) to +1.1% (tensile). Measurements at room temperature have confirmed the presence of a cycloid for BFO thin films under low strain which is destroyed by high strain. In order to measure Néel temperature (TN) of these films, we perform experiments at different temperatures. Néel temperatures deduced from measure are in agreement with ab initio calculations [1]. However, for a film of BFO subjected to very high compressive strain (! = -4.8%), we demonstrated the presence of two polymorphic phases distorted BFO, the rhombohedral ("R-like") and other tetragonal ("T-like")[2]. This last phase exhibits a magnetic ordering temperature close to room temperature (TN ~ 360 K). [1] I. C. Infante, S. Lisenkov, B. Dupé, M. Bibes, S. Fusil, E. Jacquet, G. Geneste, S. Petit, A. Courtial, J. Juraszek, L. Bellaiche, A. Barthélémy, and B. Dkhil, Physical Review Letters, 105 (2010) 057601 [2] I.C. Infante, J. Juraszek, S. Fusil, B. Dupé, P. Gemeiner, O. Diéguez, F. Pailloux, S. Jouen, E. Jacquet, G. Geneste, J. Pacaud, J. Iñiguez, L. Bellaiche, A. Barthélémy, B. Dkhil and M. Bibes, Physical Review Letters, 107 (2011) 237601

Theoretical!determination!of!the!Electric!field/magnetic!field!phase!diagram! for!multiferroic!BiFeO3! ! ! M.!Allen*,!R.!de!Sousa! ! Department!of!Physics!and!Astronomy,!University!of!Victoria,!Victoria,!! British!Columbia!V8W!2Y2,!Canada! ! *PRESENTING!AUTHOR:[email protected]! ! ! THE! ROOM! TEMPERATURE! MULTIFERROIC! BISMUTH! FERRITE! (BIFEO3! OR! BFO)! HAS! CYCLOIDAL! SPIN! ORDER! WHEN!THE!APPLIED!MAGNETIC!AND!ELECTRIC!FIELDS!ARE!ZERO.!! IN!THIS!CONFIGURATION,!BOTH!FERROMAGNETIC! AND! ANTIFERROMAGNETIC! ORDER! PARAMETERS! AVERAGE! OUT! TO! ZERO! OVER! THE! PERIOD! OF! THE! CYCLOID.!!

PREVIOUS! EXPERIMENTS! HAVE! SHOWN! THAT! THE! EXTERNAL! MAGNETIC! FIELD! NECESSARY! FOR! INDUCING! A! TRANSITION!TO!A!HOMOGENEOUS!STATE!WITH!NON"ZERO!FERROMAGNETISM!IS!OF!THE!ORDER!OF! B=20! TESLA.!! MOREOVER,!OUR!RECENT!THEORY!PREDICTED!THAT!AN!EXTERNAL!ELECTRIC!FIELD! E! ~! 105! V/CM!CAN!INDUCE!A! SIMILAR! TRANSITION! AT! B=0.! ! WE! HAVE! CALCULATED! THE! E"B! PHASE! DIAGRAM! FOR! BFO! USING! STEEPEST! DESCENT! METHODS.! ! WHEN! BFO! IS! SUBJECT! TO! MODERATE! E! AND! B! FIELDS,! THE! COMPETING! INTERACTIONS! INTERFERE! IN! SUCH! A! WAY! THAT! THE! SYSTEM! TRANSITIONS! INTO! THE! HOMOGENEOUS! STATE! AT! LOWER! FIELD! INTENSITIES.!

! THIS!WORK!WAS!SUPPORTED!BY!THE!NSERC!DISCOVERY!PROGRAM.!!

Strain!and!interface!effects!in!CoFe2O4"based!multilayers:!a!DFT+U!study! ! R.!Arras ,!L.!Calmels! ! CEMES, CNRS and Université de Toulouse, BP 94347, 31055 Toulouse Cedex 4, France! ! *!presenting!author:[email protected]! ! *

! !

Cobalt!ferrite!CoFe2O4!is!a!ferrimagnetic!insulator!with!a!high!Curie!temperature!of!

793! K.! With! such! properties,! this! material! is! potentially! very! interesting! for! oxide"based! spintronic! applications:! it! could! for! instance! be! used! as! a! spin! filtering! barrier! in! magnetic! tunnel! junctions! [1,2]! or,! be! coupled! with! ferroelectric! materials,! like! BaTiO3! [3],! in! extrinsically! magnetoelectric! and! multiferroic! multilayers.! In! order! to! understand! the! behaviour! of! CoFe2O4! in! such! complicated! devices,! we! must! first! study! how! its! properties! can! change! depending! on! the! substrate:! Recent! experiments! on! nanometer! thick! CoFe2O4! layers! have! in! particular! shown! that! the! substrate! can! play! an! important! role! and! can! influence! the! magnetic! anisotropy! [4,5].! We! have! performed! GGA+U! calculations! with! the! first!principles!code!Wien2k![6]!in!order!to!consider!both!the!effects!of!strain!and!chemical! changes!at!the!(001)!interface!between!CoFe2O4!and!some!oxide!substrates!(like!MgAl2O4).! We! will! describe! how! the! spin! magnetic! moments,! atomic! structure! and! electron! states! change!in!the!vicinity!of!these!interfaces.! References:! [1]!A.!V.!Ramos,!et!al.,!Appl.!Phys.!Lett.!91,!122107!(2007).! [2]!S.!Matzen,!et!al.,!Appl.!Phys.!Lett.!101,!042409!(2012).! [3]!Yi!Zhang,!et!al.,!Appl.!Phys.!Lett.!92,!062911(2008).! [4]!W.!Huang,!et!al.,!Appl.!Phys.!Lett.!89,!262506!(2006).!! [5]!S.!Matzen,!et!al.,!Appl.!Phys.!Lett.!99,!052514!(2011).!! [6]!P.!Blaha,!et!al.,!Wien2k,!an!augmented!planewave!+!local!orbitals!program!for!calculating! crystal!properties.!(Karlheinz!Schwarz,!Technische!Universität!Wien,!Austria,!2001).! !

Substrate influence in the physical properties of ferromagnetic/ferroelectric multilayers. L. Avilés Félix1*, J. I. González Sutter1, E. E. Kaul1, N. Haberkorn1, M. Sirena1, L. B. Steren2, N. Bergeal3, J. Lesueur3, R. Bernard4 and J. Briatico4. 1 Centro Atómico Bariloche & Instituto Balseiro, CNEA-UNC, 8400 S.C. de Bariloche, Argentina 2 Depto. Materia Condensada, Centro Atómico Constituyentes, CNEA, 1650 San Martín, Argentina 3 Consejo Nacional de Investigaciones Científicas y Técnicas, C1033AAJ Buenos Aires, Argentina 4 UPR5-LPEM-CNRS, Physique Quantique, ESPCI, 75231 Paris, France

* : presenting author ; [email protected] La0.67Mn0.33MnO3 (ferromagnetic) / Ba1-xSrxTiO3 (ferroelectric) bilayers and multilayers were grown by sputtering over different substrates. The influence of the substrate and the layers thicknesses in the physical properties of FE/FM multilayers were studied by magnetization and transport techniques. A phenomenological approach [1] is used to analyze the electrical transport in ferromagnetic (FM)/ferroelectric (FE) bilayers, using conductive atomic force microscopy (CAFM). Structural and electrical characterization of ultra-thin ferroelectric layers grown over ferromagnetic electrodes is critical for the development of multiferroic tunnel junctions. [1] M. Sirena, Journal of Applied Physics, 110, 063923 (2011).

Current distributions for FM/FE bilayers with different barrier thicknesses grown over MgO and STO.

Field!effect"modulation"of"exchange"bias"and"conductivity"" at"ferroelectric/ferromagnetic"interfaces" ! L.!Bégon"Lours*,!P.!Altuntas,!A.!Crassous,!S.!Fusil,!K.!Bouzehouane,!E.!Jacquet,!M.!Bibes,!A.!Barthélémy! and!J.!E.!Villegas! Unité!Mixte!de!Physique!CNRS/Thales,!1!av!Augustin!Fresnel,!91767!Palaiseau!Cedex! *!presenting!author:[email protected]! !

!

The! strongly"correlated! nature! of! d! electrons! in! complex! oxides! allows! the! manipulation! of! physical! properties!such!as!magnetism!and!superconductivity!via!the!field"effect!modulation!of!the!charge!carrier! density! ! [1].! ! Here! we! investigate! field"effects! at! the! interface! between! the! ferromagnet! La0,67Sr0,33MnO3! (LSMO)! and! the! ferroelectric! BiFeO3! (BFO)! in! BFO/LSMO//STO! thin! film! heterostructures! ! [2,3].! ! We! found! that! this! system! exhibits! magnetic! exchange! bias! ! [4]! in! the! temperature! range! T 100! K,! whose! magnitude! ! is! modulated! upon! switching! the! BFO’s! out! of! plane! polarization.!This!is!controlled!by!applying!voltages!with!a!conductive"tip!atomic!force!microscope!![5].! The!exchange!bias!modulation!is!accompanied!by!a!large!modulation!of!the!LSMO!conductivity!(up!to!a! factor! of! 2.2! at! room! temperature).! The! different! scenarios! that! allow! for! an! understanding! of! these! effects!will!be!discussed.! Work!supported!by!the!DIM!Oxymore!(Région!Ile"de"France)! ! [1]! C.!H.!Ahn,!M.!Di!Ventra,!J.!N.!Eckstein,!C.!D.!Frisbie,!M.!E.!Gershenson,!a.!M.!Goldman,!I.!H.! Inoue,!J.!Mannhart,!A.!J.!Millis,!A.!F.!Morpurgo,!D.!Natelson,!and!J."M.!Triscone,!Rev.!Mod.!Phys.!78,! 1185–1212!(2006).! [2]! S.!M.!Wu,!S.!a!Cybart,!P.!Yu,!M.!D.!Rossell,!J.!X.!Zhang,!R.!Ramesh,!and!R.!C.!Dynes,!Nature!Mater.! 9,!756–61!(2010).! J.!Heron,!M.!Trassin,!K.!Ashraf,!M.!Gajek,!Q.!He,!S.!Yang,!D.!Nikonov,!Y."H.!Chu,!S.!Salahuddin,! [3]! and!R.!Ramesh,!Phys.!Rev.!Lett.!107,!217202!(2011).! [4]! H.!Béa,!M.!Bibes,!F.!Ott,!B.!Dupé,!X."H.!Zhu,!S.!Petit,!S.!Fusil,!C.!Deranlot,!K.!Bouzehouane,!and!A.! Barthélémy,!Phys.!Rev.!Lett.!100,!017204!(2008).! [5]! A.!Crassous,!R.!Bernard,!S.!Fusil,!K.!Bouzehouane,!D.!Le!Bourdais,!S.!Enouz"Vedrenne,!J.!Briatico,! M.!Bibes,!A.!Barthélémy,!and!J.!Villegas,!Phys.!Rev.!Lett.!95,!247002!(2011).!!

Zinc!ferrite,!a!semiconducting,!magnetic!oxide!for!spintronics? Michael!Bonholzer*,!Kerstin!Brachwitz,!Annette!Setzer,!Pablo!Esquinazi,!Michael!Lorenz!and! Marius!Grundmann Universität!Leipzig,!Institut!für!Experimentelle!Physik!II,!Linnéstr.!5,!04103!Leipzig *presenting!author:[email protected]"leipzig.de

Bulk! zinc! ferrite! (ZnFe2O4,! ZFO)! is! known! as! an! antiferromagnetic! insulator! with! normal! spinel! structure! [1,2].! However,! ZFO! thin! films! grown! by! pulsed! laser! deposition! at! low! oxygen!partial!pressures!show!semiconducting!behaviour!of!the!conductivity![1,3,4]. The! conductivity! can! be! tuned! over! several! orders! of! magnitude! by! changing! the! growth! conditions! [3,4].! Magnetism! in! thin! films! is! also! affected! by! growth! conditions! and! shows! different! properties! compared! to! bulk! as! well.! Zinc! ferrite! thin! films! have! a! ferrimagnetic! magnetization! curve! with! a! high! saturation! magnetization! of! 100! emu/cm3! and! a! coercive! field!of!about!10mT!at!room!temperature.!Curie!temperature!is!expected!to!be!well!above! 800K! [2,3].! The! unexpected! properties! can! be! explained! by! disorder! caused! by! oxygen! vacancies! [2,3].! Interestingly,! theoretical! calculations! predict! the! semiconducting! and! ferrimagnetic! behaviour! of! slightly! distorted! zinc! ferrite.! They! also! predict! a! high! spin! polarization![5]. The!properties!make!zinc!ferrite!a!promising!material!for!spintronic!applications.!First!results! on! magnetic! tunnel! junctions! consisting! of! a! zinc! ferrite! bottom! electrode,! a! magnesium! oxide!barrier!and!a!cobalt!top!electrode!show!a!tunnel!magnetoresistance!up!to!25%. [1]!A.!Marcu!et!al.,!J.!Appl.!Phys.!102,!023713!(2007) [2]!C.E.!Rodríguez!Torres!et!al.,!Phys.!Rev.!B!84,!064404!(2011) [3]!M.!Lorenz!et!al.,!Phys.!Status!Solidi!RRL!5,!438!(2011) [4]!K.!Brachwitz!et!al.,!Appl.!Phys.!Letters!102,!172104!(2013) [5]!S.!Soliman!et!al.,!Phys.!Rev.!B!83,!085205!(2011)

A!FERROLECTRIC!MEMRISTOR! ! ! 1 1 1 S.!Boyn *,!A.!Chanthbouala ,!S.!Fusil ,!K.!Bouzehouane1,!X.!Moya2,!S.!Xavier3,!H.!Yamada4,! C. Deranlot1,!S.!Girod1,!N.D.!Mathur2,!V.!Garcia1,!J.!Grollier1,!A.!Barthélémy1!and!M.!Bibes1! ! 1! Unité!Mixte!de!Physique!CNRS/Thales,!Palaiseau!and!Université!Paris"Sud,!Orsay!(France)! 2 !Department!of!Materials!Science,!University!of!Cambridge!(UK)! 3! Thales!Research!and!Technology,!Palaiseau!(France)! 4 !AIST,!Tsukuba!(Japan)! ! *presenting!author:[email protected]! ! ! Memristors! are! continuously! tunable! resistors! that! can! be! used! to! emulate! synapses.! Conceptualized!in!the!1970s,!they!traditionally!operate!by!voltage"induced!displacements!of! matter.! Purely! electronic! memristors! have! recently! emerged! based! on! well"established! physical! phenomena! with! albeit! modest! resistance! changes.! We! will! show! that! voltage" controlled!domain!configurations!ferroelectric!tunnel!barriers![1]!yield!memristive!behaviour! with!resistance!variations!exceeding!four!orders!of!magnitude!at!10!ns!operation!speed![2].! The!tunneling!current!is!influenced!by!the!polarization!direction![3]!enabling!a!simple!non" destructive! readout! of! the! polarization! state.! Using! models! of! ferroelectric"domain! nucleation! and! growth,! we! explain!the! quasi"continuous! resistance! variations! and! derive! a! simple!analytical!expression!for!the!memristive!effect.! Experiments!have!been!conducted!on!two!types!of!tunnel!junctions:!highly"strained!ultrathin! BaTiO3![2]! and! super"tetragonal! BiFeO3! tunnel! barriers![4].! Both! show! stable,! multistate! switching.! Higher! resistance! ratios! are! obtained! with! BiFeO3! at! even! lower! voltages! than! those! applied! for! BaTiO3.! We! will! present! comparative! PFM! and! purely! electrical! measurements!of!the!switching!characteristics.! ! [1]!V.!Garcia!et!al.,!Nature!460,!81!(2009)! [2]! A.! Chanthbouala! et! al.,! Nature! Nanotechnology! 7,! 101! (2012),! A.! Chanthbouala! et! al.,! Nature!Materials!11,!860!(2012)! [3]!E.Y.!Tsymbal!and!H.!Kohlstedt,!Science!313!(2006)! [4]!H.!Yamada!et!al.,!ACS!Nano!7,!5385!(2013)!

Magneto-polaron response of La2/3Ca1/3MnO3 thin films B. Casals, D. Pesquera, J. M. Caicedo, F. Sánchez, J. Fontcuberta, G. Herranz* *Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, Bellaterra 08193, Catalonia, Spain. [email protected]

We have shown recently that optical spectroscopy under magnetic fields is a powerful tool to investigate the electronic transport of strongly electronic correlated systems at optical frequencies (visible wavelengths) [1-3]. By exploiting this technique we have demonstrated the close correspondence between the magneto-optical spectral response and the magnetic-dependence of polaron conductivity in a number of different oxides. Here, we have extended these studies to carry out a detailed analysis of magneto-polaron conductance in a single material, the ferromagnetic manganite with La2/3Ca1/3MnO3 (LCMO) composition. For that purpose, we have analyzed the magneto-optical spectral response of LCMO thin films of different thickness grown on SrTiO 3 crystal substrates of different crystal orientations, namely 001- and 110oriented substrates. In this way, we could study the evolution of the magneto-polaron contribution to the electronic transport as a function of different parameters, including different strain states as well as the role of electronic and chemistry disorder in the optical response. This analysis has confirmed the crucial influence of the electronlattice coupling on the prominence of the magneto-polaron conductance, especially relevant around the Curie temperature. These results show that magneto-optical spectroscopy may be an instrumental approach to analyze metal-insulator transitions in ferromagnets under a different perspective.

[1] D. Hrabovsky et al., Phys. Rev. B 79, 052401 (2009). [2] J. M. Caicedo et al., New J. Phys. 12, 103023 (2010). [3] J. M. Caicedo et al., Phys. Rev. B 82, 140410 (2010).

In!situ"characterization"of"ferroelectric"domain"properties"of"epitaxially" BaTiO3"(100)"ultrathin"films"on"Pt(100)"by"PFM,"STM"and"STS"under"UHV" " conditions" ! M.!CHRISTL1*,!A.!TRÜTZSCHLER1,2,!S.!FÖRSTER1,!E.M.!ZOLLNER1,!AND!W.!WIDDRA1,2! ! 1 !INSTITUTE!OF!PHYSICS,!MARTIN"LUTHER"UNIVERSITÄT!HALLE"WITTENBERG," Von"Danckelmann"Platz!3,!06120!Halle!(Saale),!Germany! 2 !Max!Planck!Institute!of!Microstructure!Physics,! WEINBERG!2,!06120!HALLE!(SAALE),!GERMANY" " *PRESENTING!AUTHOR:[email protected]"HALLE.DE" " SO! FAR,! NEARLY! ALL! FERROELECTRIC! CHARACTERIZATIONS! BY! PIEZORESPONSE! FORCE! MICROSCOPY! (PFM)! HAVE! BEEN! PERFORMED! EX"SITU! UNDER! AMBIENT! CONDITIONS! [1].! HOWEVER! ADSORBATES! CAN! INFLUENCE! THE! INTRINSIC! FERROELECTRIC! DOMAIN! STRUCTURE! OR! THE! SWITCHING! PROCESS! [2].! IN! CONTRAST,! WELL"DEFINED! SURFACE! TERMINATIONS! CAN! BE! PREPARED! UNDER! ULTRA"HIGH! VACUUM! (UHV)! CONDITIONS.! UNDER! THESE! CONDITIONS! THE! COMBINATION! OF! SCANNING! TUNNELING! MICROSCOPY! (STM)! AND! SCANNING! TUNNELING! SPECTROSCOPY! (STS)! WITH! PFM! MIGHT! ALLOW! A! DEEPER! CHARACTERIZATION! OF! FERROELECTRIC! DOMAINS,! DOMAIN!WALLS!AND!SWITCHING!PROPERTIES!AT!THE!NANOSCALE.! " BaTiO3! (100)! ultrathin! films! have! been! grown! in"situ! by! magnetron"sputtering! on! Pt(100)! substrates! [3].! Their! stoichiometry! and! structure! have! been! controlled! by! core! level! spectroscopy! (XPS! and! AES)! and! low"energy! electron! diffraction! (LEED).! Due! to! the! lattice! misfit! of! 2! %,! 10! nm! thick! BaTiO3! films! grow! compressed! and! exhibit! a! ferroelectric! c+"c"! nanodomain! configuration.! Stable! large"scale! c+! and! c"! domains! have! been! successfully! written! and! characterized! with! PFM.! Local! remnant! hysteresis! curves! show! a! pronounced! electric!field!bias!of!outward!and!inward!polarized!c!domains,!which!indicate!that!c"!domains! are!stabilized!in!the!Pt(100)"BaTiO3!(100)"vacuum!geometry.!Both!the!intrinsic!structure!and! the! poled! domain! structures! correlate! with! the! topography! which! may! correspond! to! different!local!terminations,!variations!of!the!structural!ordering!or!changes!of!the!unit"cell! high.! The! local! conductivity! has! been! found! to! be! correlated! to! the! polarization! direction! where!c"!domains!display!a!higher!conducting!state,!than!c+!domains.!Alternatively,!the!STM! can! be! used! to! write! domain! structures! by! applying! higher! STM! bias! voltages.! A! clear! contrast!between!positively!and!negatively!poled!areas!becomes!visible!in!STS!dI/dV!maps.! Via! an! apparent! height! contrast! downward! polarized! areas! appear! higher! in! the! STM! topography.! [1]!A.!Gruverman!et!al.,!Nano!Letters!9,!3539!(2009)! [2]!X.!Sun!et!al.,!Journal!of!Applied!Physics!110,!014103!(2011)! [3]!S.!Förster!et!al.,!Journal!of!Chemical!Physics!135,!104701!(2011)! !

Band!gap"engineering"of"La!based"perovskites"through"B!site"doping" ! ! 1* 1 R.!Comes ,!K.!H.!L.!Zhang ,!Y.!Du2,!T.!Droubay1,!S.!Chambers1,2! ! 1! Fundamental!and!Computational!Sciences!Directorate,!Pacific!Northwest!National! Laboratory,!Richland,!WA!USA! 2! Environmental!and!Molecular!Sciences!Laboratory,!Pacific!Northwest!National!Laboratory,! Richland,!WA!USA! ! *presenting!author:[email protected]! ! ! ! ! Complex!oxide!thin!films!offer!a!wide!variety!of!functional!properties!to!study!for!use! in! future! electronic! and! alternative! energy! technologies.! Further! research! into! these! properties!may!prove!particularly!rewarding,!as!perovskite!oxides!of!the!form!LaMO3!are!an! intriguing! candidate! for! use! in! both! solar! photovoltaic! cells! and! hydrogen! cells.! To! further! these!goals,!the!ability!to!engineer!the!band!gap!in!these!oxides!is!needed.!Traditionally,!this! has! been! accomplished! through! A"site! doping! with! an! alkaline! earth! metal! like! Sr,! as! in! (La,Sr)MnO3,!which!induces!a!change!in!the!Mn!valence!state!from!3+!to!4+!and!dopes!the! material! with! holes.! However,! recent! results! have! shown! that! alloying! two! materials! with! different!transition!metal!ions!on!the!B!site,!such!as!LaCrO3!and!LaFeO3,!can!produce!novel! electronic!properties!not!observed!in!either!of!the!constituent!materials.!To!examine!these! properties,! a! series! of! epitaxial! La(Cr,Fe)O3! films! were! grown! using! oxide! molecular! beam! epitaxy!on!SrTiO3!(STO)!(001)!and!(111)!substrates.!Films!with!varying!ratios!of!Cr!to!Fe!were! characterized!via!x"ray!photoelectron!spectroscopy!and!optical!absorption!to!determine!the! valence!band!structures.!X"ray!diffraction!has!been!performed!to!examine!chemical!ordering! on!the!B"site,!which!has!been!observed!by!others!for!double!perovskite!La2CrFeO6.!LaCrO3" LaFeO3! bilayer! structures! have! also! been! grown! to! characterize! interfacial! effects! for! potential!applications!in!superlattice!structures.!

Electrocaloric!Materials!and!Devices! ! S.!Crossley1*,!S.!Kar"Narayan1,!R.!W.!Whatmore2!and!N.!D.!Mathur1! ! 1!Materials!Science,!University!of!Cambridge! 2!Tyndall!National!Institute,!Cork,!Ireland! ! ! *presenting!author:[email protected]! !

Electrocaloric!materials!can!become!hot!or!cold!in!response!to!an!applied!electric!field.!Large! electrocaloric! effects! are! associated! with! electrically! driven! entropic! ferroelectric! phase! transitions.! As! these! effects! are! nominally! reversible,! they! have! been! suggested! for! electrically!driven!solid"state!cooling.!The!largest!electrocaloric!effects!have!been!observed! in! thin! films,! which! possess! a! small! thermal! mass! and! are! normally! studied! indirectly! via! thermodynamic! analysis! of! electrical! data.! Bulk! materials! show! orthogonal! properties,! i.e.! relatively!small!electrocaloric!effects!and!large!thermal!mass.!I!will!present!the!results!of!a! high"resolution!investigation!into!the!electrocaloric!properties!of!bulk!materials!such!as!the! ceramic! Pb! Sc0.5Ta0.5O3,! using! both! direct! and! indirect! measurements.! This! work! has! the! potential! to! enhance! mechanistic! understanding,! and! improve! the! interpretation! of! electrical!data.!!

Structural!transformations!in!the!orthorhombic!Ga2"xFexO3!system! ! Anna!Demchenko*,!Alexandre!Thomasson,!Olivier!Marconot,!Corinne!Ulhaq"Bouillet,! Christophe!Lefevre,!Francois!Roulland,!Christian!Meny,!Gilles!Versini,!Sophie!Barre,!Nathalie! Viart! ! Institut!de!Physique!de!Chimie!des!Matériaux!de!Strasbourg,!UMR!7504!CNRS"UdS,!23,!rue! du!Loess,!BP!43,!67034!Strasbourg!Cedex!2,!France! ! *!presenting!author:[email protected]! ! ! ! ! Ga2"xFexO3! is! a! magnetoelectric! material! presenting! a! net! magnetization! at! room! temperature! for! x>1.3.! These! materials! have! huge! importance! in! basic! sciences! and! applications! in! spintronic! devices.! It! is! therefore! very! promising! in! terms! of! applications! in! magnetoelectric! random! access! memories.! Our! group! has! mastered! its! elaboration! in! thin! films!onto!conducting!(111)!Pt!buffered!(111)!YSZ!substrates!by!both!pulsed!laser!deposition! and!sputtering.!The!material!crystallizes!in!the!orthorhombic!Pc21n!space!group.!The!growth! is!along!the!(010)!axis!and!we!only!observe!3!variants!in"plane.!We!will!present!the!results!of! our!study!of!these!thin!films!by!transmission!electron!microscopy!(TEM).!!! Both! plane! views! and! cross! sections! observations! unveil! the! crystallographic! relationships! between!the!three!variants,!onto!which!rely!the!magnetic!properties!of!the!films.! We! will! also! show! the! influence! of! the! TEM! samples! preparation! method! onto! the! observations.!When!the!sample!is!thinned!by!ion!milling!a!phase!transformation!from!Pc21n! to! Fd"3m! takes! place.! This! phase! transformation! will! be! studied! in! the! light! of! the! crystallographic!proximity!between!the!epsilon"Fe2O3!(Pc21n)!and!gamma"Fe2O3!(Fd"3m).! !

Investigations of the polarization sensitive surface band structure of doped BaTiO3(001) with full-field electron spectromicroscopy Jelle Dionot1,2, Julien Rault1, Claire Mathieu1, Vitaliy Feyer3 and Nick Barrett1 1

CEA/IRAMIS/SPCSI/LENSIS, F-91191 Gif-sur-Yvette, France 2 Université Paris-Sud, F-91405 Orsay, France 3 IFF-1 and IAS-1, Research Center Jülich GmbH, D-52425 Jülich, Germany

Ferroelectric (FE) materials exhibit a spontaneous electric polarization which can be switchable under the application of an external electric field or through chemical potential changes [1,2] which make them of intense interest for uses in electronics as well as in catalysis. However, the surface electronic screening mechanisms which can stabilize the ferroelectricity are far from being well known. By using the archetypal ferroelectric barium titanate (BaTiO3), we have studied the FE domain-dependent surface chemistry and electronic band structure for various oxygen vacancy-induced doping levels.

II’

I’

I II

(a)

(b)

(c)

Coupled with the highly collimated and tunable X-ray synchrotron source, PhotoEmission Electron Microscopy in direct (PEEM) and reciprocal space (k-PEEM) can give great insight to the properties of such materials thanks to the surface and chemical specificity. With high spatial and energy resolution, we could relate the surface stoichiometry with the FE domain ordering (a), map the work function (b), measure the full two-dimensional, polarization sensitive electronic band structure of BaTiO3 single crystal of various doping levels (c) [3,4]. First-principles calculations based on the density functional theory (DFT) showed good agreement with the experimental results, and complementary simulations were so far performed to further understand the fundamentals of the FE ordering in BTO perfect single crystals. REFERENCES 1. 2. 3. 4.

R. V. Wang et al., Physical Review Letters 102, p. 047601 (2009). M. J. Highland et al., Physical Review Letters 107, p. 187602 (2011). N. Barrett and O. Renault, Matériaux et Techniques 97, pp. 101-122 (2009). A. Damascelli, Physica Scripta T109, pp. 61-74 (2004).

Characterisation!of!domain!and!domain!wall!conductivity!in! ferroelectric!materials!

! Alan!Douglas*,!Li"Wu!Chang,!Amit!Kumar,!Marty!Gregg! Centre!for!Nanostructured!Media,!Queens!University!Belfast,!Belfast,!Northern!Ireland! *

presenting!author:[email protected]!

! An!investigation!into!the!fabrication!and!characterization!of!ferroelectric!heterostructures!was! carried! out.!The! materials!of! choice!were!a!combination!of!ultrathin!barium!titanate!(BaTiO3)! and!strontium!ruthenate,!a!ferroelectric!and!bottom!electrode!layer!respectfully;!this!structure! was! deposited! on! a! substrate! of! Strontium! Titanate! by! pulsed! laser! deposition.! Samples! of! mixed!tetragonal!and!rhombohedral!bismuth!ferrite!(BiFeO3)![2]!and!ultrathin!BaTiO3![3]!!provided! from!outside!sources!were!also!investigated.! Domains! and! domain! walls! within! the! materials! were! then! investigated! using! both! PFM! and! ambient! scanning! tunneling! microscopy! (STM),! with! the! intention! of! being! able! to! measure! domain!wall!conductivity!and!investigate!the!factors!which!control!conductivity.!The!STM!has! not!been!widely!utilized!for!domain!wall!studies! [4]1due!to!the!inherent!nature!of!ferroelectrics! being!insulators,!but!with!the!right!samples!it!allows!both!high"resolution!conductivity!mapping! and!direct!probing!of!the!densities!of!states!within!the!domain!walls.! Striving! for! a! better! understanding! and! control! over! ferroelectric! domain! walls! will! no! doubt! prove!of!use,!as!it!will!enable!us!to!better!integrate!such!components!into!an!newly!emerging! generation!of!nanoscale!electronic!devices.!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !2.!Chiu,!Y.P.!et!al.!"Atomic"Scale!Evolution!of!Local!Electronic!Structure!Across!Multiferroic!Domain!Walls."!Ad" vanced!Materials!23,!1530–1534!(2011).! ! 3.!!Sample!provided!by!Dr.!D.!Majumdar!(University!of!Alabama)! ! 4.!Sample!provided!by!Prof.!Chang"Beom!Eom!(University!of!Wisconsin"Madison)!and!Prof.!Alexei!Gruverman!(Uni" versity!of!Nebraska"Lincoln)!

Structural!characterization!of!rutile!TiO2!on!GaN!templated!Si!(111)! ! ! 1* 1 K.!Elibol ,!G.!Koster ,!R.!Hueting2,!M.!Nguyen1,!and!G.!Rijnders1! ! 1 Faculty!of!Science!&!Technology!and!MESA+!Institute!for!Nanotechnology,!University!of! Twente,!P.O.!Box!217,!7500!AE,!Enschede,!The!Netherlands! ! 2 Electrical!Engineering,!Mathematics!and!Computer!Science!and!MESA+!Institute!for! Nanotechnology,!University!of!Twente,!P.O.!Box!217,!7500!AE,!Enschede,!The!Netherlands! ! *presenting!author:[email protected]! ! ! ! ! Materials!such!as!TiO2!have!to!be!used!as!a!buffer!layer!on!GaN!to!avoid!large!lattice! mismatch! and! inter"diffusion! between! perovskite! oxides! and! GaN.! TiO2! is! investigated! as! candidate!buffer!layer!for!integration!of!perovskite!ferroelectrics!on!GaN.!This!study!focuses! on!structural!and!surface!properties!of!TiO2on!GaN/Si!substrate.!Firstly,!TiO2!thin!films!were! grown! on! GaN/Si.! Structural! and! surface! properties! of! TiO2! films! are! investigated! by! using! AFM! and! XRD.! Subsequently,! the! interface,! the! growth! mode,! composition,! thickness,! and! surface! defects! of! optimized! TiO2! thin! films! on! GaN/Si! are! investigated! by! using! HRTEM,! RHEED,! XPS,! HR"SEM,! STM.! Preliminary! results! show! that! in! particular! the! deposition! pressure! is! an! important! parameter,! which! determines! the! crystallinity! of! the! thin! films,! possibly!related!to!changes!in!surface!diffusivity!and!sticking.!

The!Coherence!Length!of!the!2D!Superconductor!at!the!LaAlO3" SrTiO3!Hetero"Interface!

!

! ! Evangelos!Fillis"Tsirakis1*,!Hans!Boschker1,!Christoph!Richter2,!Jochen!Mannhart1! ! ! 1 Max!Planck!Institute!for!Solid!State!Research,!Germany! !2University!of!Augsburg,!Germany! ! *presenting!author:[email protected]! ! !

! ! !!The! interface! between! the! oxides! LaAlO3! and! SrTiO3,! two! band! insulators! of! perovskite! structure! with! similar! lattice! constants,! has! been! long! investigated.! The! two! dimensional! electron!liquid!formed!at!this!interface!is!metallic!and!also!superconducting!at!temperatures! roughly! below! 300! mK.! We! studied! the! superconductivity"induced! gap! in! the! density"of" states! of! this! 2D! electron! system! by! means! of! tunnelling! spectroscopy.! In! particular,! the! magnetic!field!dependence!of!the!superconducting!gap!was!studied!with!the!magnetic!field! applied!perpendicular!to!the!interface.!The!superconducting!gap!disappears!with!increasing! magnetic!field!and!this!allows!us!to!determine!the!upper!critical!field!Hc2,!which!is!directly! related! to! the! superconducting! coherence! length! in! a! type! II! superconductor.! The! superconductivity!can!be!tuned!by!electric!field!doping!and!the!gate!voltage!dependence!of! the!coherence!length!will!be!discussed.!

!“Organosol”!synthesis!and!Properties!of!Nanocrystalline!Barium!Strontium! Titanate!Ceramics!with!Ultrafine!Grain!Size!by!Spark!Plasma!Sintering!!! ! ! Yanling!Gao!1,*,!Vladimir!V.!Shvartsman!2,!Devendraprakash!Gautam!3᧨Markus!Winterer!4! and!Doru!C.!Lupascu!5! 1,2,5 !Institute!for!Materials!Science,!University!Duisburg"Essen,!45141!Essen,!Germany! 3,4 !Nanoparticle!Process!Technology,!Universität!Duisburg"Essen,!Lotharstrasse!1,!47057! Duisburg,!Germany!and!CENIDE,!Center!for!Nanointegration!Duisburg"Essen! ! ! ! *presenting!author:!yanling.gao@uni"due.de! 2 !vladimir.shvartsman@uni"due.de! 3 !devendraprakash.gautam@uni"due.de! 4 !markus.winterer@uni"due.de! 5 !doru.lupascu@uni"due.de! ! ! ! Dense! nanocrystalline! ceramics! with! an! average! grain! size! around! 40! nm! were! obtained! starting! from! non"agglomerated! nanopowders! and! using! a! low"temperature! sintering! process.! The! synthesis! and! properties! of! barium! strontium! titanate,! Ba0.6Sr0.4TiO3,! (BST)! ceramics! are! reported.! The! dense! nanoceramics! were! prepared! by! spark! plasma! sintering! (SPS)!at!950!and!1050!°C!from!nanopowders!(~20!nm),!which!were!synthesized!by!a!modified! “Organosol”! process.! The! grain! size! of! the! nanocrystalline! ceramics! was! estimated! from! scanning!electron!microscopy!(SEM)!pictures!of!the!etched!surfaces.!X"ray!diffraction!(XRD)! and!dielectric!measurements!in!the!temperature!range!173"313!K!in!combination!with!SEM! images!were!used!to!investigate!the!evolution!of!the!crystal!structure!and!the!ferroelectric! (FE)!"!to!"!paraelectric!(PE)!phase!transformation!behavior!with!different!grain!size:! in plane directions are observed. Changing to buffered HF as etching reactant results in coherent step-and-terrace structures along the [1-10] direction. We will also discuss the possibility that different substrate treatments result in different surface stoichiometry of the SrTiO3 substrate, influencing the initial growth of the films. Investigating how the symmetry of the (111)-oriented surface affects the magnetic properties, we image magnetic domains by X-ray photoemission electron microscopy (X-PEEM). The films revealed large magnetic domains (>100m), with the [11-2] direction as an easy axis. The in-plane magnetization reversal is observed to be a non-continuous step-wise switching process with intermediate domain stages. The relationship between these intermediate domain states and the underlying crystal symmetry will be assessed.!




































































  















































      
































   


 

 

 
 








 



  
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Study!of!local!polarization!in!LSMO/BTO!interfaces! J.!Tornos1,!G.!Sanchez"Santolino1!,!D.!Hernández1*,!M.!Cabero1*,!Z.!Sefrioui1,!M.!Varela1,2,!S.!J.! Pennycook2,!C.!Leon1,!J.!Santamaría1! *:!David!Hernández:[email protected],!Mariona!Cabero:[email protected]! ! 1 !GFMC,!Universidad!Complutense!de!Madrid,!Madrid!28040,!Spain.! 2 !Oak!Ridge!National!Laboratory,!Oak!Ridge!TN!37831,!USA.! !

Complex!oxide!interfaces!exhibit!a!number!of!novel,!exciting!properties!such!as!the!2D!metallic!state! found! in! the! LaAlO3/SrTiO3! interface! [1].! These! physical! behaviors! are! directly! related! to! the! interface! structure! and! also! to! defects,! such! as! O! vacancies.! Here,! we! present! the! study! of! multiferroic!La0.7Sr0.3MnO3!/!BaTiO3! (LSMO/BTO)!ferromagnetic/ferroelectric!heterostructures!where! the!polarization!in!the!BTO!layers!is!determined!by!interfacial!effects.!!In!these!systems!the!interplay! between! magnetic,! electric! and! transport! properties! may! result! in! novel! functionalities! and! multiferroic!tunnel!junctions![2].!For!example,!the!ferroelectric!polarization!can!affect!the!tunneling! magnetoresistance,! resulting! in! two! different! resistance! states! for! each! magnetic! state! (parallel! or! antiparallel)! of! the! magnetization! of! the! electrodes.! Aberration"corrected! scanning! transmission! electron! microscopy! combined! with! electron! energy! loss! spectroscopy! has! been! used! to! study! the! structure,! chemistry! and! electronic! properties! of! this! system,! with! atomic! resolution! and! in! real! space.! Spectroscopic! measurements! suggest! the! presence! of! O! vacancies! through! the! ferroelectric! layers,!and!a!domain!structure!can!be!observed!in!annular!bright!field!images,!which!are!sensitive!to! small! O! displacements.! The! domain! walls! can! induce! a! lattice! relaxation! which! may! trigger! flexoelectric!polarization![3"6].!The!understanding!of!the!flexoelectric!effect!and!its!coupling!to!the! charge!carriers!associated!to!the!oxygen!vacancies!may!be!the!key!to!control!the!dynamics!of!domain! walls.! ! References:! ! [1]!A.!Ohtomo!and!H.!Y.!Hwang,!Nature!427,!423"426!(2004).! ! [2]!V.!Garcia,!M.!Bibes!et!al.,!Science!327,1106–1110!(2010).! ! [3]!G.!Catalan,!J.!Seidel,!R.!Ramesh!and!J.!F.!Scott,!Rev.!Mod.!Phys.!84,!119"156!(2012)!.! ! [4]!C."L.!Jia!et!al.,!Nature!Materials!7,!57"61!(2008).! ! [5]!R.!Thomas,!J.!F.!Scott,!D.!N.!Bose!and!R.!S.!Katiyar,!J.!Phys.:!Condens.!Matter!22,!423201!(2010).! ! [6]!H.!Lu!et!al.,!Science!336,!59"61!(2012).!

! This! work! was! supported! by! the! Division! of! Materials! Sciences! and! Engineering! of! the! US! Department! of! Energy!(MV!and!SJP).!Work!at!Complutense!University!sponsored!by!the!European!Research!Council!Starting! Investigator!Award.!

!

Electrical Spin Injection at Ferromagnet/Oxide/Semiconductor Interfaces probed by Magnetoresistance and Spin-Pumping Experiments H. Jaffrès1,*, J. Peiro1, J.-M. George1, and M. Jamet2 1

Unité Mixte de Physique CNRS/Thales, 1 Av. A. Fresnel, 91767 Palaiseau, France 2 INAC/NM CEA, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France * presenting author: [email protected]

In the focus of spintronics with semiconductors, a proper electrical spin injection into the conduction band of semiconductors is essential for exploring new functionalities like the electrical manipulation by a gate voltage and electrical detection of a spin current between ferromagnetic source and drain. Among semiconductors, Ge is a material of a great interest for high carrier mobility, long spin diffusion length and large spin-orbit coupling to perform electric field spin manipulation through Rashba interactions. The up-to-date studies in various group IV (Si and Ge) and III-V (GaAs) systems concern the measurement of the spin accumulation created by injecting a current at ferromagnetic/oxide/semiconductor interfaces by a three-point electrical Hanle and inverted Hanle techniques[1-3]. In the main systems investigated worldwide, the strong spin amplification evidenced at a single interface is related to a two-step spin injection process through a band-tail of evanescent electronic states at the specific oxide/semiconductor interface. In my presentation, combining magnetoresistance and spin-pumping experimental techniques, we will show how, and unlike in GaAs systems, an efficient spin injection can be reached in the conduction band of Ge despite the presence of interface states [4-5]. We reveal a clear transition from spin injection into electronic states in GOI at the interface with CoFeB/MgO spin injector [5]. Beyond a spin signal amplification at low temperature, we observe a clear transition to a spin injection in the channel above 200K up to room temperature. In this temperature range, the spin signal is reduced to a value compatible with spin diffusion model. Even more interesting we could demonstrate a direct spin injection in the conduction band in Ge through spin-pumping effects and inverted spinhall mechanism involving the ferromagnetic resonance of the CoFeB layer [5]. In the end, in a more global approach and unlike in metallic tunnel junctions, I will emphasize on the physics of spin injection into semiconductors by spin pumping effects involving a large band of localized states at the interface with the tunnel barrier and whose presence is necessary to induce spin accumulation in the semiconductor region. [1] X. Lou, C. Adelmann, M. Furis, S. A. Crooker, C. J. Palmstrøm, and P. A. Crowell, Phys. Rev. Lett. 96, 176603 (2006). [2] M. Tran, H. Jaffrès, C. Deranlot, J.-M. George, A. Fert, A. Miard, and A. Lemaître, Phys. Rev. Lett. 102, 036601 (2009). [3] S. P. Dash, S. Sharma, J. C. Le Breton, J. Peiro, H. Jaffrès, J.-M. George, A. Lemaître, and R. Jansen, Phys. Rev. B84, 054410 (2011). [4] A. Jain et al., Appl. Phys. Lett. 99, 162102 (2011). [5] A. Jain et al., Phys. Rev. Lett. 109, 106603 (2012).

PZT!thin!films!for!capacitive!RF"MEMS! ! ! ! C.!Jégou ,!L.!Michalas ,!T.!Maroutian ,!G.!Agnus1,!M.!Koutsoureli2,!G.!Papaioannou2,!L.! Largeau3,!A.!Leuliet4,!P.!Aubert1,!Ph.!Lecoeur1! ! 1! Institut!d’Electronique!Fondamentale,!Univ!Paris"Sud,!CNRS!UMR!8622,!F"91405!Orsay! Cedex,!France!;! 2 !Solid!State!Physics!Section,!Physics!Department,!National!and!Kapodistrian!University!of! Athens,!Panepistimiopolis!Zografos,!Athens!15784,!Greece!;! 3 !Laboratoire!de!Photonique!et!Nanostructures,!CNRS!UPR!20,!F"91460!Marcoussis,!France!;! 4! Thales!Research!&!Technology!France,!F"91767!Palaiseau!Cedex,!France.! ! *!presenting!author:!carole.jegou@u"psud.fr! ! ! ! Lead! zirconate! titanate! (PZT)! is! an! attractive! material! for! capacitive! RF"MEMS! applications! due! to! its! high! permittivity.! The! PZT! layer! has! first! to! be! integrated! on! metallic! lines,! in! particular!on!gold!lines!for!RF!devices.!One!of!the!main!concerns!is!then!the!control!of!the! leakage!currents!through!the!full!stack!including!electrodes!and!PZT!film.!! In!this!context,!we!studied!the!leakage!current!through!a!PZT!layer!with!Pt!electrodes!in!the! 230"340K!temperature!range!in!order!to!assess!the!conduction!mechanisms.!PZT!thin!films! were! grown! by! pulsed! laser! deposition! with! a! La0.67Sr0.33MnO3! (LSMO)! buffer! layer! on! epitaxial! Pt! (111).! The! oxide! buffer! layer! is! necessary! in! order! to! avoid! the! formation! of! a! parasitic!pyrochlore!phase,!while!a!Pt!layer!is!compatible!with!gold!RF!lines.!X"Ray!diffraction! and! transmission! electron! microscopy! evidenced! a! columnar! growth! of! (001)"! and! (011)" oriented! PZT! grains.! The! leakage! current! through! the! Pt/PZT/LSMO/Pt! structure! was! then! systematically!measured.!From!current!vs.!time!curves!a!temperature"dependent!threshold! voltage! was! found! below! which! stable! and! reproducible! current! values! are! obtained,! thus! avoiding! resistance! degradation.! The! conduction! mechanism! changes! from! bulk"controlled! around! room! temperature! to! interface"controlled! at! low! temperatures.! Hopping"type! conductivity! evidenced! above! 270K! is! consistent! with! the! extended! defects! and! columnar! microstructure!of!the!PZT!film.! 1*

2

1

2!dimensional"electron"gas"at"the"interface"of"oxide"semiconductors:(Mg," Zn)O/ZnO"heterostructures" ̘ A.!Leveratto1*,!E.!Bellingeri1,!G.!Gadaleta1,!G.!Scicolone1,!I.!Pallecchi1,!L.!Pellegrino1,!D.! Marré1,!A.!Jost2,!U.!Zeitler2!!

̘ 1!CNR"SPIN!corso!Perrone!24,!16152!Genova,!Italy!and!Dipartimento!di!Fisica,!Via! Dodecaneso!33,!16146!Genova,!Italy̘  2

!High!Field!Magnet!Laboratory,!Institute!for!Molecules!and!Materials,!Radboud!University! Nijmegen,!6525!ED!Nijmegen,!The!Netherlands! *:!presenting!author;[email protected]

Recently,!two"dimensional!electron!gases!(2DEG)!in!oxide!heterostructures!have!attracted!a! lot! of! attention.! Among! the! investigated! heterostructures! ZnO! based! multilayers! unambiguously! showed! the! presence! of! a! 2DEG! at! the! interface! [1,! 2].! Such! heterostructures! resemble! to! GaAs! or! GaN! based! systems;! at! the! ̘ Zn1"xMgxO/ZnO! heterointerface! a! strong! built"in! potential! arises! from! macroscopic! polarization! mismatch! and! bands! align! because! of! different! bandgaps! in! the! two! layers! (0.6! eV),! causing! the! formation!of!a!potential!well!at!the!interface!where!a!2DEGs!is!confined.! Here! we! present! the! realization! of! ZnO/MgxZn1"xO! (x=0.15)! heterostructures! deposited! by! pulsed!laser!deposition!on!Zn"polar!ZnO!single!crystal.!In!detail,!we!show!the!optimization!of! substrate!treatments!and!the!optimization!of!deposition!parameters!necessary!to!optimize! the!film!growth.!The!films!are!in"situ!monitored!by!RHEED!and!routinely!checked!ex"situ!by! AFM,! and! XRD! measures.! Our! samples! show! clear! Shubnikov"de! Haas! Oscillations! and! Quantum! Hall! Effect! behaviour.! By! analysing! transport! properties! measurement! we! evaluate! sheet! carrier! densities! of! about! n2D=1012! [cm"2]! and! mobility! values! in! the! range,! 10000![cm2V"1s"1].!Quantum!phenomena,!are!surprisingly!observed!up!to!20K.!Finally,!for!the! first!time!in!an!oxide!based!2DEG,!quantum!oscillations!are!observed!also!in!thermoelectric! power!and!Nernst!coefficient.!! [1]!A.!Tsukazaki!et!al,!Science!315,!1388!(2007)! [2]!A.!Tsukazaki!et!al.Physical!Review!B!78,!233308!(2008)!

Uniaxial!Strain!Induced!Ferroelectric!Phase!with!a!Giant!Axial!Ratio!in!(110)! BiFeO3!Thin!Film! ! Huajun!Liu1*,!Ping!Yang2,!Zhen!Fan1,!Amit!Kumar3,!Kui!Yao4,!Khuong!Phuong!Ong5,!! Kaiyang!Zeng3!and!John!Wang1! ! 1! Department!of!Materials!Science!and!Engineering,!National!University!of!Singapore,! Singapore! 2 !Singapore!Synchrotron!Light!Source!(SSLS),!National!University!of!Singapore,!Singapore! 3 !Department!of!Mechanical!Engineering,!National!University!of!Singapore,!Singapore! 4 !Institute!of!Materials!Research!and!Engineering,!A*STAR!(Agency!for!Science,!Technology! and!Research),!Singapore! 5 !Institute!of!High!Performance!Computing,!A*STAR!(Agency!for!Science,!Technology!and! Research),!Singapore! ! *presenting!author:[email protected]! ! ! Strain! engineering,! which! employs! biaxial! misfit! strain! to! deform! the! crystal! structure,! is! a! powerful!tool!to!tune!the!physical!behavior!of!epitaxial!thin!films.!Here!we!show!that!a!10" nm"thick!BiFeO3!film!is!uniaxially!strained!by!(110)"oriented!LaAlO3!substrate,!which!exhibits! a! monoclinic! lattice! with! a! giant! c/a! ~! 1.24! and! a! unique! stripe! ferroelectric! domain! configuration,!as!revealed!by!high!resolution!synchrotron!X"ray!diffraction!and!piezoelectric! force! microscopy.! A! strain"phase! diagram! for! BiFeO3! under! uniaxial! strain! condition! is! predicted!by!first!principles!calculations,!suggesting!that!monoclinic!Pm!phase!with!a!large! polarization!of!~!130!!C/cm2!is!the!lowest"in"energy!phase!when!strained!by!(110)"oriented! LaAlO3!substrate.!Our!results!provide!a!potential!route!to!tune!physical!behavior!of!epitaxial! ferroelectric!thin!films!by!uniaxial!strain!in!(110)!orientation,!instead!of!widely!investigated! biaxial!strain!in!(001)!orientation.!! !

Effect!of!a!built"in!electric!field!in!asymmetric!ferroelectric!tunnel!junctions! Y.!Liu1,2*,!X.!J.!Lou2,!I.!C.!Infante1,!M.!Bibes3,!B.!Dkhil1! 1!

Laboratoire!Structures,!Propriétés!et!Modélisation!des!Solides,!UMR!8580!CNRS,!Ecole! Centrale!Paris,!92295!Châtenay"Malabry,!France! !2 !Multi"disciplinary!Materials!Research!Center,!Frontier!Institute!of!Science!and!Technology,! Xi'an!Jiaotong!University,!Xi'an!710054,!People's!Republic!of!China! 3 !Unité!Mixte!de!Physique!CNRS/Thales,!1!Av.!A.!Fresnel,!91767!Palaiseau!! and!Université!Paris"Sud,!91405!Orsay,!France! ! ! *!presenting!author:[email protected] or [email protected]! ! ! ! The! research! in! ferroelectric! tunnel! junctions! (FTJs)! has! been! intensified! recently.! As! pointed! out! in! the! early! 30’s! by! Simmons1,! the! contribution! of! different! electronic! and! chemical! environments! of! the! asymmetric! electrode/insulator! interfaces! would! induce! a! large!built"in!electric!field!in!thin!insulators,!being!more!significant!in!asymmetric!junctions.! In! the! present! work2! we! propose! a! systematic! study! of! the! role! of! the! built"in! field! in! the! particular!case!of!asymmetric!FTJs.! Using! a! multiscale! thermodynamic! model,! we! demonstrate! that! a! critical! thickness! exists! at! which! an! unusual! first"order! like! ferroelectric"“polar! non"ferroelectric”! phase! transition!occurs!in!asymmetric!FTJs.!In!the!“polar!non"ferroelectric”!phase,!there!is!only!one! non"switchable! polarization! which! is! caused! by! the! competition! between! the! depolarizing! field!and!the!built"in!field,!and!closure"like!domains!being!proposed!to!minimize!the!system! energy.! We! evaluate! the! dependence! of! the! transition! temperatureon! the! ferroelectric! barrier! thickness,! which! becomes!more! significant! for! the! thinner! ferroelectric! layers.! As! a! matter!of!fact,!the!built"in!electric!field!does!not!only!result!in!smearing!the!phase!transition! but! also! forcing! the! transition! to! take! place! at! a! reduced! temperature.! Such! findings! may! impose!a!fundamental!limit!on!the!working"temperature!and!thus!it!should!be!further!taken! into!account!in!the!future!FTJs"type!or!ferroelectric!capacitor"type!devices.! !

1

J.!G.!Simmons,!“Intrinsic!fields!in!thin!insulating!films!between!dissimilar!electrodes”,!Phy.!Rev.!Lett,!vol.!10,!p.! 10"12,!1963.! 2 Y.! Liu,! X.! J.! Lou,! M.! Bibes,! and! B.! Dkhil,! “Effect! of! a! built"in! electric! field! in! asymmetric! ferroelectric! tunnel! junctions”,Phy.!Rev.!B,!vol.!88,!p.!024106,!2013.!

!

From!high"Tc!superconductors!to!topological!insulators!"!!! two!decades!pulsed!laser!deposition!of!functional!oxides!in!Leipzig! ! ! * Michael!Lorenz ,!Marcus!Jenderka,!Marius!Grundmann! ! Semiconductor!Physics!Group,!Institut!für!Experimentelle!Physik!II,!Universität!Leipzig! ! *presenting!author:[email protected]"leipzig.de! ! ! ! ! Only! two! years! after! Venky’s! famous! initial! boost,! the! work! on! Pulsed! Laser! Deposition!in!Leipzig!started!in!a!laser"ionization!mass!spectrometer!(see!also![1]).!As!a!first! highlight!of!the!development!of!advanced!PLD!processes!appeared!high"performance!large" area! and! double"sided! YBCO! thin! films! up! to! an! area! of! 71! x! 75! mm2! for! microwave! applications![2].!After!wide"bandgap!oxide!semiconductors!became!the!focus!of!work,!high! Hall! mobilities! of! heteroepitaxial! ZnO! thin! films! were! achieved! by! introducing! low" temperature! buffer! layers! in! a! multi"step! PLD! process! [3].! A! flexible! high"pressure! PLD! process! allows! the! growth! of! nanowire! heterostructures! with! controlled! aspect! ratio! [4].! Both! ZnO! nanostructures! and! thin! films! became! the! base! for! extended! investigations! of! optical! whispering! gallery! modes! [5].! Transparent,! oxide"based! electronic! devices! were! processed! based! on! crystalline! and! amorphous! oxide! thin! films,! such! as! ZnO:Mg! and! ZnCo2O4.! Other! recent! PLD"based! investigations! [6]! include! magnetic! semiconductors! such! as!ZnFe2O4,!multiferroic!composites!and!multilayers![7],!and!topological!insulator!oxide!thin! films!based!on!iridates![8].!! ! [1]!M.!Lorenz!et!al.!Procedia!Engineering!(2013)!MRS!Singapore!"!ICMAT!Symposia!Proc.! [2]!M.!Lorenz!et!al.!APL!68,!3332!(1996)! [3]!E.!M.!Kaidashev!et!al.!APL!82,!3901!(2003)! [4]!M.!Lorenz!et!al.!APL!86,!143113!(2005)! [5]!T.!Nobis!et!al.!PRL!93,!103903!(2004)!! [6]!M.!Lorenz,!R.!Rao!(guest!eds.)!Special!issue!"25!years!PLD"!J.!Phys.!D:!Appl.!Phys!(2013)! [7]!M.!Lorenz!et!al.!CrystEngComm!14,!6477!(2012)! [8]!M.!Jenderka!et!al.!PRB!88,!045111!(2013)!

Role!of!electron!correlation!of!FeO!at!Fe/ferroelectric!oxide/Fe!interface!for! magnetic!transport!properties

A.!Neroni*,!D.!Wortmann,!E.!Sasioglu,!S!.Blügel,!M.!Le\aic Peter!Grünberg!Institut!and!Institute!for!Advanced!Simulation,!Forschungszentrum!Jülich!and! JARA,!52425!Jülich,!Germany * presenting!author:!a.neroni@fz"juelich.de

! Fe/ferroelectric! oxide/Fe! is! a! nanoferronic! tunnel! junction! with! exciting! electronic! magneto"conductive!transport!properties.!FeO!layer!at!the!interface!of!Fe/oxide/Fe!barriers! seems!to!significantly!alter!these!properties!as!indicated!by!several!experiments.!In!order!to! understand! the! role! of! electron! correlations! in! FeO! at! the! interface! we! use! an! embedded! Green"function!approach![1]!implemented!with!the!framework!of!the!full"potential!linearized! augmented!plane"wave!(FLAPW)! method! FLEUR! [2]! to! obtain! the! tunneling! properties! of! a! Fe/BaTiO /Fe!barrier.!Conductances!are!obtained!for!different!oxidation!conditions!and!for! 3 different!magnetic!configurations!of!the!contacts.!Strong!correlations!are!taken!into!account! employing!the!LDA+U!approach!within!the!framework!of!the!density!functional!theory!(DFT)! with!a!Hubbard!U!parameter!determined!by!constrained!random!phase!approximation!(cRPA)! [3]. Work!is!supported!by!Helmholtz!Young!Investigators!Group!Program!VH"NG"409. [1]!www.flapw.de [2]!D.!Wortmann,!H.!Ishida,!and!S.!Blügel,!PRB!65,!165103!(2002) [3]!E.!Sasioglu,!C.!Friedrich,!and!S.!Blügel,!PRB!83,!121101(R)!(2011)

Novel!formation!method!of!oxide!films! using!nonequilibrium!atmospheric!pressure!plasma! ! ! * Y.!Nose ,!N.!Fujimura! ! Osaka!Prefecture!University! ! *presenting!author:[email protected]"u.ac.jp! ! ! ! Zinc!oxide!(ZnO)!is!one!of!the!most!indispensable!materials!in!the!field!of!transparent! oxide!electronics!such!as!a!transparent!conductive!layer!and!a!thin!film!transistor!because! ZnO!films!with!strong!(0001)!preferred!orientation!can!be!easily!obtained!at!low!deposition! temperature! without! the! effect! of! epitaxy! (self"texture).! However,! ZnO! films! have! non" stoichiometric! problem! due! to! the! low! formation! energy! of! donor! defects! such! as! oxygen! vacancy!(VO)!or!zinc!interstitial!(Zni),!which!is!the!biggest!obstacles!for!the!realization!of!ZnO" based! unipolar! devices! in! spite! of! its! quite! excellent! exitonic! properties.! Up! to! now,! magnetron! sputtering! method! has! been! the! most! popular! growth! technique! of! ZnO! films! because! of! its! high! productivity! and! low! deposition! temperature.! However,! such! a! plasma! process!operated!at!low!pressure!requires!the!use!of!vacuum!equipment,!which!decreases! the!throughput,!increases!the!running!cost!and!also!has!an!issue!regarding!ion!peening!effect! by! ion! bombardment.! Therefore,! development! of! plasma! processes! operated! near! atmospheric! pressure! (AP)! is! strongly! desired.! Here,! we! propose! a! novel! formation! technique!of!ZnO!films!using!non"equilibrium!AP!N2!/!O2!plasma.!In!the!poster!session,!we! present! the! electrical! and! optical! properties! of! ZnO! films! grown! by! our! home"made! CVD! system!and!discuss!the!future!scopes!of!this!deposition!technique.!

Modulation!of!transport!and!magnetism!in!La0.825Sr0.175MnO3!thin!films! induced!via!ferroelectric!switching!! ! ! * D.!Preziosi ,!M.Alexe!and!D.Hesse! ! Max"Planck"Institut!für!Mikrostrukturphysik!!Weinberg!2,!D"06120!Halle,!Germany! ! *!presenting!author:!preziosi@mpi"halle.de! ! ! As!already!shown!in!several!papers!by!different!authors,!the!fascinating!interplay!between! spin,!charge!and!orbital!degree!of!freedom!in!strongly!correlated!materials!can!be!modified! when!the!polarization!of!a!ferroelectric!oxide,!used!as!gate!material,!is!reversed.!As!a!result!a! modulation!in!the!resistivity!and!in!the!magnetization!values!of!the!correlated!material!can! be! measured.! Hall! bar! patterned! hetero"structures! of! La0.825Sr0.175MnO3! (LSMO)! and! PbZr0.2Ti0.8O3! (PZT)! were! fabricated.! Transport! and! magnetic! measurements! show! that! the! switching! of! the! PZT! polarization! significantly! influences! the! competing! electronic! ground! states!of!the!LSMO,!modulating!the!resistivity!value!as!well!as!the!magnetization!one.!Hall! coefficient! measurements! performed! in! both! polarization! directions! give! practically! the! same!value!of!charge!carrier!density.!As!a!result!it!can!be!argued!that!the!modulation!in!the! transport!and!magnetic!properties!of!the!LSMO!may!not!be!charge"driven!but!due!to!other! mechanisms.!!! ! ! ! ! ! !

Hysteretic transport in manganite/graphene hybrid planar nanostructures M. Rocci1,2*, A. Perez Muñoz1,2*, J. Tornos1,2, N.M. Nemes1,2, A. Rivera-Calzada1,2, Z. Sefrioui1,2, M. Clement2,3, E. Iborra2,3, C. León1,2 and J. Santamaría1,2 1

2

CEI Campus Moncloa, UCM-UPM, Madrid, Spain. G.F.M.C., Facultad de Ciencias Físicas – Universidad Complutense de Madrid, Madrid 28040, Spain 3 G.M.M.E., E.T.S.I.T., Universidad Politécnica de Madrid, Madrid 28040, Spain

* : Mirko Rocci, Ana Perez Muñoz; [email protected], [email protected]

We report on the fabrication and magnetotransport characterization of innovative hybrid graphene-based planar nanodevices with epitaxial nanopatterned La0.7Sr0.3MnO3 manganite, grown on SrTiO3 (100), as ferromagnetic current injector electrodes. The few layers graphene (FLG) was deposited onto the predefined manganite nanowires by using the PMMA transfer technique. These nanodevices exhibit hysteretic transport as measured by IV curves. The resistance can be reversibly switched between high and low states yielding a consistent non-volatile memory response.

Preparation!and!characterization!of!confined!electronic!states!at!the!(001),! (110)!&!(111)!surface!of!SrTiO3  T.C.!Rödel1!*,!C.!Bareille1,!F.!Fortuna1,!F.!Bertran2,!M.Gabay3,!M.!Rozenberg3,!! T.!Maroutain4,!P.!Lecoeur4,!A.F.!Santander"Syro1!! ! 1!CSNSM,!Université!Paris"Sud!and!CNRS/IN2P3,!

Bâtiments!104!et!108,!91405!Orsay!cedex,!France! 2!Synchrotron!SOLEIL,!L’Orme!des!Merisiers,! Saint"Aubin"BP48,!91192!Gif"sur"Yvette,!France! 3!Laboratoire!de!Physique!des!Solides,! Université!Paris"Sud,!Bâtiment!510,!91405!Orsay,!France! 4!Institut!d’Electronique!Fondamentale,! Université!Paris"Sud,!Bâtiment!220,!91405!Orsay,!France! ! ! *!presenting!author:[email protected]!   The!two"dimensional!electron!gases!(2DEGs)!in!transition"metal!oxide!(TMO)!interfaces!are!a! field! of! current! intense! research.! They! can! present! remarkable! properties,! such! as! superconductivity!or!magnetoresistance.!!However,!the!microscopic!origin!of!such!interfacial! metallic!states!is!still!controversial.! The!recent!discovery,!via!angle"resolved!photoemission!spectroscopy!(ARPES),!of!a!2DEG!that! is!formed!at!the!(001)!surface!of!vacuum"fractured!single!crystals!of!insulating!SrTiO3!opened! a!new!avenue!for!the!understanding!and!fabrication!of!2DEGs!in!TMOs.! To!explore!2DEGs!at!surfaces!of!TMOs!other!than!SrTiO3! (001),!fracturing!the!sample!is!not! always! a! feasible! technique.! As! many! TMOs! have! highly! polar! surfaces! and/or! no! natural! cleaving! plane,! fracturing! leads! in! many! cases! to! disordered! surfaces,! thus! preventing! the! formation! of! a! 2DEG.! To! circumvent! this,! we! prepared! the! (001),(110)! &! (111)! surface! of! SrTiO3!using!a!chemical!and!thermal!treatment. The! confined! electronic! states! formed! at! these! surfaces! are! characterized! by! ARPES.! The! obtained! Fermi! surfaces! at! the! (110)! &! (111)! surface! of! SrTiO3! are! very! different! from! the! one! of! the! well"studied! (001)! surface.! Thus,! the! properties! of! the! confined! states! can! be! tailored!by!changing!the!confinement!direction.!These!results!motivate!further!research!on! the!electronic!states!at!the!(110)!and!(111)!surface!as!well!as!the!SrTiO3"based!interfaces!as! novel!physics!might!be!within!reach.!!!!

Electro!Optical"Response"and"Strain!Dependent"Optical"Properties"of" Multiferroic"BiFeO3"Thin"Films" ! D.!Sando1*,!P.!Hermet2,!J.!Allibe1,!C.!Carrétéro1,!E.!Jacquet1,!J.!Bourderionnet3,!J."C.!Mage1,! Ph.!Ghosez2,!A.!Barthélémy1,!and!M.!Bibes1! ! 1 Unité!Mixte!de!Physique!CNRS/Thales,!1!avenue!A.!Fresnel!91767!Palaiseau,!France! 2

Département!de!Physique,!Université!de!Liège,!B"5,!B"4000!Sart"Tilman,!Belgium! 3

Thales!Research!&!Technology,!1!avenue!A.!Fresnel,!91767!Palaiseau,!France!

! *presenting!author:[email protected]! ! The! room"temperature! multiferroic! bismuth! ferrite! (BiFeO3! –! BFO)! is! proving! to! be! an! extremely! versatile! multifunctional! oxide! [1].! It! is! an! outstanding! ferroelectric! with! polarization! of! 100! µC/cm2,! and! it! displays! G"type! antiferromagnetic! ordering! with! a! cycloidal! modulation! of! the! Fe! spins.! In! addition! to! its! strong! promise! in! spintronics,! it! exhibits! potentially! valuable! optical! properties.! Characteristics! of! interest! include! a! visible! range!band!gap,!low!absorption!in!the!infra"red!range,!and!a!large!birefringence,!as!well!as! attractive! photovoltaic! properties.! These! optical! properties! make! BFO! an! interesting! candidate!as!the!active!medium!in!thin!film!integrated!electro"optic!modulators![2].!For!this! application,!it!is!important!to!have!a!detailed!understanding!of!the!electro"optical!response! of!the!medium,!that!is,!the!change!in!the!refractive!index!when!an!electric!field!is!applied!–! the! so"called! electro"optic! (EO)! coefficients.! To! date,! the! EO! coefficients! of! BFO! have! not! been!reported.! Another! aspect! of! particular! interest! is! the! dependence! of! the! BFO! material! properties! on! misfit!strain.!Strain!can!drastically!modify!many!physical!properties!of!epitaxial!thin!films;!a! striking!example!being!the!strong!reduction!of!the!Curie!temperature!TC!of!BFO!under!strong! compressive!strain![3].!It!has!also!been!shown!that!strain,!through!its!effect!of!distorting!the! lattice! structure,! can! cause! a! rotation! in! the! direction! of! polarization,! and! thus! the! z" component!of!the!polarization!can!be!controlled!by!strain.!Experimentally,!strain!engineering! can!be!implemented!by!growing!thin!films!of!BFO!on!various!substrates!that!impose!a!wide! range!(4%)!of!strains!ranging!from!compressive!to!tensile.! We!will!first!describe!our!efforts!in!experimentally!determining!the!electro"optic!coefficients! of!BFO!using!two!different!sample!orientations!and!symmetries,!and!compare!our!results!to! those!of!first"principles!calculations.!In!addition!to!the!electro"optical!properties,!we!discuss! the! potential! of! strain! engineering! for! optimizing! the! optical! properties! of! BFO! thin! films.! Using! ellipsometry! and! transmission! spectroscopy! measurements! we! characterize! our! samples! and! observe! a! systematic! trend! of! the! optical! band! gap! with! strain.! Lastly,! we! discuss! the! potential! of! making! use! of! the! presented! results! to! incorporate! this! multifunctional!material!into!thin!film!integrated!optical!devices.! ! References! [1]!!!G.!Catalan!and!J.F.!Scott,!Adv.!Mater.!21,!1!(2009)! [2]!!!J.!Allibe!et!al.,!Appl.!Phys.!Lett.!96,!182902!(2010)! [3]!!!I.C.!Infante!et!al.,!Phys.!Rev.!Lett.!105!(2010),!057601!

Ferroelectric!and!magnetic!properties!of!doped!BiFeO3!and!BiFeO3/BaTiO3! composite!and!multilayer!thin!films! ! ! P.!Schwinkendorf1*,!M.!Lorenz1,!V.!Lazenka2,!H.!Hochmuth1,!M.Ziese1,!M.!Grundmann1! ! 1! Institut!für!Experimentelle!Physik!II,!Universität!Leipzig! 2 !Institute!for!Nanoscale!Physics!and!Chemistry!(INPAC),!KU!Leuven! ! *!presenting!author:[email protected]"leipzig.de! ! ! ! BiFeO3! is! to! date! the! most! widely! studied! single! phase! material! concerning! potential! application! as! multiferroic! in! the! development! of! upcoming! new! computer! memory! technologies.! This! is! due! to! its! unique! combination! of! room! temperature! ferroelectricity! (polarization!values!of!up!to!60!µC!cm"2)!and!ferromagnetism![1].! However,!single!phase!BiFeO3!films!are!often!suffering!from!high!leakage!currents.!In!order! to! overcome! this! problem! and! possibly! modify! the! basic! ferroelectric! and! magnetic! properties,! fabrication! of! composite! films! and! multilayer! heterostructures! is! worth! to! be! studyied![2].!We!present!our!investigation!of!composite!thin!films!and!multilayers!consisting! of!BiFeO3!and!BaTiO3!as!well!as!doping!of!BiFeO3!films!with!rare!earth!ions![3].! As!expected,!a!high!BaTiO3!content!in!the!samples!is!able!to!decrease!the!leakage!current.! We!furthermore!found!that!multilayers!exhibit!considerably!enhanced!magnetic!properties! compared! to! single! phase! films.! The! same! is! observed! for! Gd"doped! films! while! La"doping! causes! smoothening! of! the! film! surface! which! may! be! important! for! several! potential! applications![3].!! ! [1]! Wang!J.!et!al.!;!Science!299,!1719!(2003)! [2]! Lawes!G.!et!al.!;!J.!Phys.!D:!Appl.!Phys.!44,!243001!(2011)! [3]! Lazenka!V.!et!al.!;!J.!Phys.!D:!Appl.!Phys.!46!175006!(2013)!

Two-dimensional electron gas at the interface between two wide-bandgap insulators M. Scigaj1, N. Dix1, J. Gázquez1, M. Varela2,3, N. Bergeal4, J. Lesueur4, F. Sánchez1, J. Fontcuberta1, G. Herranz1 1 Institut de Ciència de Materials de Barcelona, ICMAB-CSIC Campus de la UAB, Bellaterra 08193, Catalonia, Spain 2 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA 3

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Dpt. Física Aplicada III, Universidad Complutense de Madrid, Madrid, 28040 Spain LPEM-UMR8213/CNRS-ESPCI ParisTech-UPMC, 10 rue Vauquelin-75005 Paris, France *E-mail: [email protected]

A high-mobility two-dimensional electron liquid (2DEL) was discovered a few years ago at the LaAlO3/SrTiO3 (LAO/STO) interface [1]. This unexpected interface conductivity between the two wide-bandgap insulators has been widely accepted to be originated by electronic charge transfer driven by the polarity discontinuity across the (001)-oriented LAO/STO interface. The beauty and simplicity of such a model has probably stimulated the deep investigation mostly in (001)-oriented LAO/STO, with exceptionally very few other interfaces, such as (001) LaGaO3/STO and LnTiO3/STO (Ln rare earth) [2, 3]. We demonstrate here that the family of high-mobility 2DELs in oxide interfaces can be expanded to other growth orientations. Specifically, we demonstrate that, above a critical thickness, 2DELs are also generated in epitaxial (111)- and (110)- oriented LAO/STO interfaces, with sheet carrier density and mobility values very similar to the (001) interfaces [4]. We also report on superconductivity at (110)-interfaces below !"200 mK, in which the 2D nature of the electronic state is unambiguously ascertained by the Landau-Ginsburg analysis of the superconductive state under the application of magnetic fields. Our discovery of 2DEL at different crystalline orientations opens up the door to study new physics and new phenomena at interfaces, where the effects of crystal orientation on the electronic band structure and properties may be of relevance. At the same time, these findings open a new perspective for elucidating the ultimate microscopic mechanism of carrier doping. Electron microscopy work at ORNL was supported by the U.S. Department of Energy (DOE), Basic Energy Sciences (BES), Materials Sciences and Engineering Division. [1] Ohtomo, A. & Hwang. Nature 427, 423–426 (2004) [2] Perna, P. et al., Appl. Phys. Lett. 97, 152111 (2010). [3] Jang, H. W. et al., Science 331, 886–889 (2011). [4] G. Herranz et al., Scientific Reports 2 758 (2012).

! Influence!of!substrate–film!interface!engineering!on!the!!!!!!!!! multiferroic!BiFeO3! Alim!Solmaz1*,!Mark!Huijben1,!Beatriz!Noheda2,!Guus!Rijnders1! 1

Mesa+!Institute!for!Nanotechnology!,!University!of!Twente,!Enschede,!The!Netherlands! Zernike!Institute!for!Advanced!Materials,!University!of!Groningen,!Groningen,!The!Netherlands!

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*presenting!author:[email protected]! ! In!our!work,!we!focus!on!the!heteroepitaxial!growth!of!BiFeO3!single!crystal!thin!films!on!SrTiO3! substrates! by! pulsed! laser! deposition.! We! demonstrate! that! the! initial! BiFeO3! growth! is! very! sensitive! to! the! terminating! layer! of! the! substrate.! Singly! TiO2"terminated! substrates! can! be! switched!to!SrO!termination!by!interval!deposition!with!the!assistance!of!Reflective!High!Energy! Electron! Diffraction! (RHEED)! technique.! BiFeO3! thin! films! grown! on! SrO! and! TiO2! singly" terminated!substrates!show!different!morphologies!as!well!as!different!ferroelectric!domains.! This!indicates!that!the!sticking!of!bismuth!oxide!species!on!TiO2"terminated!surfaces!is!different! than! that! of! iron! oxide! on! SrO! terminated! surfaces.! This! determines! the! interface! quality! between! the! BiFeO3! thin! film! and! the! substrate.! Keeping! in! mind! that! the! interfaces! become! more!influential!as!the!film!gets!thinner,!we!emphasize!the!importance!of!interface!engineering! for!highly!controlled!multiferroic!devices.!We!claim!that,!in!BiFeO3!thin!film!growth,!the!atomic! terminating!layer!of!the!substrate!should!be!taken!into!account!as!well,!next!to!other!factors! that! are! known! to! influence! the! ferroelectric! domain! formation,! such! as! screening! charges,! lattice!mismatch!or!substrate!miscut.!

Novel!functionalities!in!LaAlO3/SrTiO3!interface ! ! 1,2* 2 2 3 3 3 4 F.!Telesio ,I.!Pallecchi ,L.!Pellegrino ,D.!Li ,!S.!Gariglio ,!J."M.!Triscone ,!!E.!Esposito ,!E.! 5 5 1,2 Di!Gennaro ,!F.!Miletto!Granozio ,!D.!Marré ! 1! Università!degli!Studi!di!Genova,!Dipartimento!di!fisica,!Via!Dodecaneso!33,!16146!Genova,! Italy 2 !CNR"SPIN,!UOS!Genova,!Corso!Perrone!24,!16152,!Genova,!Italy 3! DPMC,!University!of!Geneva,!24!Quai!Ernest"Ansermet,!1211!Geneva!4,!Switzerland 4! Istituto!di!Cibernetica!E.!Caianiello!del!CNR,!Via!Campi!Flegrei!34,!I"80078!Pozzuoli!(NA),! Italy 5! CNR"SPIN,!UOS!Napoli,!Complesso!Universitario!di!Monte!S.!Angelo,!Via!Cintia!,!80126,! Napoli,!Italy ! *presenting!author:[email protected] ! ! ! In! the! last! few! years LaAlO3/SrTiO3 (LAO/STO)! interface! has! been! massively! studied! as! a! ! ! prototypical! system! of! correlated! 2D! Electron! System.! Both! the! origin! of! the! 2DES! and! his! phenomenology! have! been! investigated:! role! of! oxygen! vacancies,! Shubnikov! de! Haas! oscillations! in! conductance,! dependence! of! mobility! by! growth! conditions,! behavior! under! gate!voltage!et!cetera. In!this!context!the!study!of!novel!functionalities,!such!as!thermoelectric!properties!and!spin! diffusion,! is! part! of! a! fundamental! investigation! of! the! properties! of! this! interface! and! can! open!perspectives!on!applications,!with!the!realization!prototypes!of!devices. We!perform!Seebeck!effect!measurements:!the!temperature!behavior!is!studied,!as!well!as! the!dependence!by!the!gate!voltage.!The!attention!is!focused!on!the!low!temperature!regime! and! the! interfaces! are! compared! with! Niobium! doped! samples,! in! order! to! investigate! the! role!of!confinement!on!thermopower. In! order! to! study! non"equilibrium! spin! transport! in! LAO/STO! interface! we! realize! fully! epitaxial! spin! valve! devices,! in! a! planar! geometry,! with! perovskitic! Lanthanum! Strontium! Manganite! as! ferromagnetic! electrode.! Several! planar! local! spin! valve! devices! with! non! magnetic!channels!of!different!width!are!realized!on!the!same!sample!in!order!to!reconstruct! spin!depolarization!profile!and!determine!the!spin!diffusion!length!in!the!interface.

VORTEX!ICE"IN"NANOPATTERNED"HIGH!TC"SUPERCONDUCTORS" ! J.!Trastoy1,*,!M.!Malnou2,!C.!Ulysse3,!R.!Bernard1,!G.!Faini3,!J.!Lesueur2,!J.!Briatico1!and!Javier! E.!Villegas1! ! 1!

Unité!Mixte!de!Physique!CNRS/Thales,!Palaiseau,!France! 2!

LPEM,!CNRS"ESPCI,!Paris,!France!

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CNRS,!Laboratoire!de!Photonique!et!de!Nanostructures,!Marcoussis,!France!

! *presenting!author:!juan.trastoy"[email protected]! !

! The!dynamics!of!magnetic!flux!quanta!on!artificial!energy!landscapes!can!be!used!as!a!model! system! to! investigate! general! problems! which! are! common! to! a! variety! of! systems! of! interacting!“particles”:!electrons,!spins,!colloids,!etc…! ! Here! we! study! a! problem! inspired! in! the! geometric! frustration! present! in! ice! systems.! In! particular,! we! investigate! the! matching! of! the! flux! lattice! to! arrays! that! present! geometric! frustration! in! the! search! for! the! “vortex! ice”! [1].! This! was! studied! through! magneto" resistance! measurements! of! YBCO! films! in! which! the! energy! landscape! is! fabricated! via! masked! ion! irradiation,! which! allows! one! to! design! the! frustrated! pinning! arrays! with! nanometric!precision![2].!! ! Our! experiments! show! field"matching! effects! that! imply! the! ordering! of! the! vortices! following! square! ice! geometry! [3].! This! realization! shows! two! unique! properties! among! artificial!ice!systems.!The!first!comes!from!the!fact!that!the!geometric!array!frustration!can! be! switched! on/off! upon! temperature! variation,! allowing! the! “freezing”! and! “melting”! of! vortex!ice.!The!second!is!that!the!depinning!and!dynamics!of!the!vortex!ice!are!insensitive!to! annealing,!which!implies!that!the!ordered!ground!state!is!spontaneously!approached.!! ! ! [1]!A.!Libál,!C.!J.!O.!Reichhardt,!and!C.!Reichhardt,!Phys.!Rev.!Lett.!102,!237004!(2009).! [2]!I.!Swiecicki,!C.!Ulysse,!T.!Wolf,!R.!Bernard,!N.!Bergeal,!J.!Briatico,!G.!Faini,!J.!Lesueur,!and! J.!E.!Villegas,!Phys.!Rev.!B!85,!224502!(2012).! [3]!J.!Trastoy!et!al.!(unpublished).! ! ! Work! supported! by! the! French! ANR! via! «!SUPERHYRBIDS"II!»! and! “MASTHER”,! and! the! Fundación!Barrié!(Galicia,!Spain)!

Studying oxides with Low Energy Electron Microscopy ! ! "#$#%#!&'(!)*+!,-++*(./!0#!%*11*23*+45/!6#$!&'(!)*+!0-2*(/!$#!"'+41! ! 7'8*+29(:!;((*1!