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Etude théorique de l'anisotropie magnétique dans des systèmes hybrides pour la spintronique moléculaire

Abstract : Magnetic anisotropy is a property of great importance both for applications (magnetic storage, ...) and for its fundamental interest. In this manuscript, we are more precisely interested in the computation of the magneto-crystalline anisotropy energy (MCA) that results from spin-orbit coupling. It is a delicate quantity to determine for several reasons : it is generally very small (of the order of meV per atom at most) and depends crucially on many physical and numerical parameters. In particular, it is strongly dependent on the symmetries of the system, the crystal lattice, but also on the nature of the materials, in this case the transition metals 3d. We are more particularly interested in magnetic thin films for which the MCA is calculated as the difference in system energy between a magnetization parallel to the surface of the material and a magnetization orthogonal to it. In particular, we use codes based on density functional theory (DFT, Quantum ESPRESSO and Quantum ATK) and a tight-binding code (TB). The MCA being obtained as an energy difference between two spin orientations using the force theorem. The objective of this PhD thesis is to understand and describe in detail the behavior of the MCA in magnetic thin films and the different ways to tune and modify (controllably or not) its magnitude. Thanks to our computational tools, we have extracted the main trends and highlighted the essential parameters that allow us to control the anisotropy. One of them is of particular interest, the hybridization of orbitals between a 3d transition metal and non-magnetic carbon atom, giving rise to important variations in anisotropy. Such systems are called hybrid-systems, and give us information on the transmission of magnetic properties (polarization, anisotropy) between neighboring atoms.
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https://tel.archives-ouvertes.fr/tel-03066790
Contributor : Ludovic Le Laurent <>
Submitted on : Tuesday, December 15, 2020 - 2:10:11 PM
Last modification on : Thursday, December 17, 2020 - 3:09:02 AM
Long-term archiving on: : Tuesday, March 16, 2021 - 7:37:56 PM

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Ludovic Le Laurent. Etude théorique de l'anisotropie magnétique dans des systèmes hybrides pour la spintronique moléculaire. Physique [physics]. Université Paris-Saclay, 2020. Français. ⟨tel-03066790⟩

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