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Theses

Transport électronique polarisé en spin dans les contacts atomiques de fer

Abstract : This thesis is dedicated to the theoretical study of spin-dependent transport in atomic contact. The main objective is to understand the giant anisotropic magnetoresistance experimentally measured in iron break junctions. On this purpose, we developed a method to calculate electron transport properties in magnetic nanostructures. The calculation is performed in two steps. First the electronic structure of the contact is determined in a basis of atomic orbitals spd using a tight-binding model extended to include magnetism. The magnetic properties are described at the atomic scale using an interelectronic interaction Hamiltonian. Two interaction models are compared : a simple Stoner-like model and a more complete Hartree-Fock model, developed to reproduce the orbital polarization effects which appear in one-dimensional nanostructure. To describe the magnetic anisotropy, noncollinear magnetism and spin-orbit coupling are taken in account. In the second step, the electron transport properties are derived in the Landauer formalism. In this approach, the transport of electron is supposed to be coherent and elastic. The conductance is directly proportional to the transmission probability of electrons through the contact. This transmission is calculated from the Green function of the system. This method is applied to the study of magnetoresistance in iron atomic contact. Several contact geometries, from the monatomic wire to realistic systems, are compared. The results reveal the importance of contact geometry and orbital polarization.
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Submitted on : Wednesday, January 28, 2009 - 5:29:20 PM
Last modification on : Friday, May 29, 2020 - 3:57:37 PM
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  • HAL Id : tel-00356826, version 1

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Gabriel Autès. Transport électronique polarisé en spin dans les contacts atomiques de fer. Matière Condensée [cond-mat]. Université Pierre et Marie Curie - Paris VI, 2008. Français. ⟨tel-00356826⟩

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