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Influence of the Epitaxial Strain on Magnetic Anisotropy in LSMO Thin Films for Spintronics Applications Sandeep Kumar Chaluvadi

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Influence of the Epitaxial Strain on Magnetic Anisotropy in LSMO Thin Films for Spintronics Applications Sandeep Kumar Chaluvadi Influence of the epitaxial strain on magnetic anisotropy in LSMO thin films for spintronics applications Sandeep Kumar Chaluvadi To cite this version: Sandeep Kumar Chaluvadi. Influence of the epitaxial strain on magnetic anisotropy inLSMO thin films for spintronics applications. Electronics. Normandie Université, 2017. English. NNT: 2017NORMC248. tel-01717569 HAL Id: tel-01717569 https://tel.archives-ouvertes.fr/tel-01717569 Submitted on 26 Feb 2018 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. THESE Pour obtenir le diplôme de doctorat Spécialité ELECTRONIQUE, MICROELECTRONIQUE, OPTIQUE ET LASERS, OPTOELECTRONIQUE MICROONDES Préparée au sein de l’ENSICAEN et de l’UNICAEN Influence of the epitaxial strain on magnetic anisotropy in LSMO thin films for spintronics applications Présentée et soutenue par Sandeep Kumar CHALUVADI Thèse soutenue publiquement le 13 décembre 2017 devant le jury composé de M. VIRET Michel Chercheur (HDR), CEA Saclay Rapporteur M. BELMEGUENAI Mohamed Maître de conférences (HDR), Université Paris 13 Rapporteur Mme MOUGIN Alexandra Directrice de recherches CNRS, Université Paris 11 Examinateur M. MAZALEYRAT Frédéric Professeur des universités, ENS Cachan Examinateur M. PERNA Paolo Chercheur, IMDEA Madrid Examinateur Mme MECHIN Laurence Directrice de recherches CNRS, Université Caen Normandie Directeur de thèse Thèse dirigée par Laurence MECHIN, laboratoire GREYC (UMR 6072) iii Contents List of Abbreviations ............................................................................................................... vii List of Symbols ......................................................................................................................... ix 1 Introduction ........................................................................................................................ 1 2 Manganite (La1-xSrxMnO3) properties ................................................................................ 5 2.1 Functional oxide perovskites ....................................................................................... 5 2.1.1 Perovskite crystal structure .................................................................................. 5 2.1.2 Phase diagram of La1-xSrxMnO3 .......................................................................... 6 2.1.3 Crystal structure and properties ........................................................................... 7 2.2 Thin films .................................................................................................................... 9 2.2.1 Epitaxy ............................................................................................................... 10 2.2.2 Growth modes .................................................................................................... 11 2.2.2.1 2D or Frank-Van der Merwe or Layer growth ........................................... 11 2.2.2.2 3D or Volmer-Weber or Island growth ...................................................... 11 2.2.2.3 2D + 3D or Stranski - Krastanov or layer + island growth ........................ 11 2.2.3 Thin film growth techniques .............................................................................. 12 2.2.3.1 Pulsed Laser Deposition (PLD) .................................................................. 12 2.2.3.2 Molecular Beam Epitaxy (MBE) ................................................................ 12 2.2.3.3 Reflection High-Energy Electron Diffraction (RHEED) ........................... 14 2.3 Strain engineering ..................................................................................................... 15 2.3.1 How to induce and/or tune strain ....................................................................... 15 2.3.2 Strain engineering due to lattice mismatch ........................................................ 16 2.3.2.1 Orbital occupancy ....................................................................................... 17 2.3.2.2 Octahedral rotations .................................................................................... 18 2.3.2.3 Electrical and magnetic properties ............................................................. 20 3 Magnetic anisotropy and Magneto-Optical Kerr Magnetometry ..................................... 23 3.1 Magnetic Anisotropy ................................................................................................. 23 3.1.1 Why does it matter…? ....................................................................................... 23 3.1.2 Factors influencing magnetic anisotropy ........................................................... 23 3.1.2.1 Shape anisotropy......................................................................................... 23 3.1.2.2 Magnetocrystalline anisotropy ................................................................... 24 3.1.2.3 Magneto-elastic anisotropy ......................................................................... 25 3.1.2.4 Surface anisotropy ...................................................................................... 25 3.1.3 Magnetic anisotropy in bulk La0.7Sr0.3MnO3 ..................................................... 26 3.1.4 Magnetic anisotropy in LSMO thin films .......................................................... 27 iv 3.1.4.1 LSMO on STO substrates ........................................................................... 27 3.1.4.2 LSMO on NGO (110) substrates ................................................................ 30 3.1.4.3 LSMO on LSAT (001) substrates ............................................................... 31 3.1.5 Summary ............................................................................................................ 32 3.2 Magneto-Optical Kerr Magnetometry ....................................................................... 33 3.2.1 MOKE Theory ................................................................................................... 33 3.2.2 MOKE configurations ........................................................................................ 34 3.2.3 Vectorial MOKE set-up @IMDEA Nanociencia, Madrid................................. 35 3.2.4 MOKE set-up @CNR-IOM, Trieste, Italy......................................................... 38 3.2.5 Stoner-Wohlfarth Model .................................................................................... 39 3.2.6 Summary ............................................................................................................ 41 4 Strain-induced by lattice mismatch in LSMO thin films .................................................. 43 4.1 Introduction ............................................................................................................... 43 4.2 Experimental details .................................................................................................. 43 4.3 LSMO films under tensile strain by PLD ................................................................. 45 4.3.1 LSMO on STO (001) ......................................................................................... 45 4.3.2 LSMO on MgO (001) ........................................................................................ 47 4.3.3 LSMO on STO buffered MgO (001) ................................................................. 48 4.4 LSMO films under compressive strain by PLD ........................................................ 50 4.4.1 LSMO on LSAT (001) ....................................................................................... 50 4.4.2 LSMO on NGO (110) ........................................................................................ 51 4.4.3 LSMO on LAO (001)......................................................................................... 53 4.5 Summary: Compressive strain vs. tensile strain........................................................ 54 5 Magnetic anisotropy of LSMO films under tensile strain grown by PLD ....................... 57 5.1 LSMO on STO (001)................................................................................................. 57 5.1.1 Magnetic characterization .................................................................................. 57 5.1.1.1 Angular dependent M (H) loops around characteristic axes @ 300 K ....... 58 5.1.1.2 Angular dependence of remanence @ 300 K ............................................. 59 5.1.1.3 Angular dependence of coercive fields @ 300 K ....................................... 60 5.1.1.4 Temperature-dependent magnetic properties ............................................. 62 5.1.2 Summary ............................................................................................................ 63 5.2 LSMO on STO buffered MgO (001)......................................................................... 64 5.2.1 Magnetic characterization .................................................................................. 64 5.2.1.1 Angular dependent M (H) loops around characteristic
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