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Anisotropie magnétique induite par modulation de surface et étude de la propagation de parois de domaines dans des nanostructures magnétiques

Abstract : A study on the induction of a magnetic anisotropy of magnetostatic origin in a magnetic thin layer (Ni81Fe19) having a modulated topology was carried out by performing magneto-transport measurements (AMR). Modulation in the nanometric scale is obtained with a new approach based on the electronic lithography. The presence of a uniaxial anisotropy along the modulation was highlighted. This latter allowed the definition of two orthogonal axes of anisotropy in the same substrate and the exploration of the feasibility of a 2D dimensional magnetic sensor. A sensor geometry based on the Planar Hall effect is proposed.
The development and the fabrication of a device allowing studying the domain wall propagation in a sub-micronic wire based on a spin-valve element have been accomplished. In such devices the domain wall position is determined by probing the Giant Magneto-Resistance (GMR). The systematic study of the injection and depinning fields showed the existence of an asymmetry in the propagation of the wall between the transitions P -> AP and AP -> P. It was shown, thanks to a series of magnetic micro simulations, that this asymmetry results from the influence of the dipolar field created by the fixed layer on the configurations adopted by the wall in the free layer. Relaxation time measurements made it possible to obtain the cumulated probability for the depinning of the domain wall from the constriction. A variety of behaviors was thus highlighted.
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Submitted on : Monday, January 26, 2009 - 4:23:15 PM
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Joel Briones Hernandez. Anisotropie magnétique induite par modulation de surface et étude de la propagation de parois de domaines dans des nanostructures magnétiques. Matière Condensée [cond-mat]. Université Henri Poincaré - Nancy 1, 2008. Français. ⟨NNT : 2008NAN10095⟩. ⟨tel-01748547v2⟩

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