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Imagerie Magnéto-optique du retournement de l'aimantation dans des couches minces de La_0,7 Sr_0,3 MnO_3

Mohammed Saib 1
1 Equipe Electronique - Laboratoire GREYC - UMR6072
GREYC - Groupe de Recherche en Informatique, Image, Automatique et Instrumentation de Caen
Abstract : This PhD thesis deals with the study and the visualization at room temperature of the magnetization reversal process within ferromagnetic manganites thin films of composition La0,7Sr0,3MnO3 (LSMO). In this work, a Magneto Optical Kerr Effect (MOKE) imaging setup was realized and a method enabling vectorial magnetization imaging was proposed. This imaging system was used to study first, the influence of the substrate, which induces strain in the film and second, the influence of the shape of the samples, on the pinning and the magnetic domain reversal process in LSMO thin films. In the case of LSAT ((LaAlO3)0.3(Sr2AlTaO6)0.7) substrate, the compressive stress in the LSMO film induces an out-of-plane magnetization component. The easy axis of magnetisation is in the plane of the film and does not depend on the direction in the plane. The in-plane magnetization switch is found to follow the coherent reversal model. In the case of STO (SrTiO3) substrate, with (001) orientation, the magnetic anisotropy is biaxial in the plane and the magnetization reversal occurs by nucleation and propagation of domain walls. In the case of vicinal STO substrates, the magnetic anisotropy becomes uniaxial and parallel to the steps on the surface of the substrate. Magnetic domain switch occurs by nucleation and propagation if the magnetic field is applied parallel to the atomic steps vicinal. When the magnetic field is applied perpendicular to the steps of the vicinal substrate, the magnetic domain switch follows the coherent reversal model. This work constitutes a first step in the understanding and the control of the magnetic behaviour of spintronic devices.
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https://tel.archives-ouvertes.fr/tel-00179291
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Submitted on : Monday, October 15, 2007 - 11:19:03 AM
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Mohammed Saib. Imagerie Magnéto-optique du retournement de l'aimantation dans des couches minces de La_0,7 Sr_0,3 MnO_3. Electronique. Université de Caen, 2007. Français. ⟨tel-00179291⟩

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