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Magnétorésistance et configuration de domaines

Abstract : In this work, we measured the domain wall induced resistivity in different kinds of ferromagnetic metals (iron, cobalt, manganese oxides, alloy of Fe0.5Pa0.5). The first circuit studied, made by electron-beam lithography, was a 4 micron long wire, 200 nanometers wide, and 50 nm nanometers thick. By magnetic force microscopy and Lorentz microscopy we were able to deduce that the domains were head-to-head in the virginal state. The wall behaviour was studied when the field was swept. By electron-beam lithography we were able to put voltage gold contacts on the wire, so that the contacts do not disturb the domains configuration. In cobalt we have measured a wall resistivity greater than predicted by theoretical models. In manganite, we measured the magnetoresistivity associated with grain boundaries. We also measured the domain wall resistivity in a thin film with perpendicular magnetic anisotropy Fe0.5Pa0.5). The domain were all directed along a specific direction. We verified some theoretical prediction on the domain wall resistivity, such as the difference induced by the direction of the current crossing the wall. We also studied magnetic systems, by experiments and calculations, where the shape anisotropy is the leading term. In triangular dots of lateral size ranging from 0.1 to 2 microns, geometrical frustration leads to the stabilization of vortex states. In iron-palladium alloy wires, we showed that the domain width is constant when the width of the wire is reduced down to 300 nanometers. However, the domains orientation becomes anisotropic and the domains walls align perpendicularly to the axis wire. Theses studies put some light on the way shape anisotropy changes the equilibrium states.
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https://tel.archives-ouvertes.fr/tel-00000860
Contributor : Marc Gingold <>
Submitted on : Tuesday, November 20, 2001 - 5:53:32 PM
Last modification on : Wednesday, December 9, 2020 - 3:08:31 PM
Long-term archiving on: : Tuesday, September 11, 2012 - 1:05:37 PM

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  • HAL Id : tel-00000860, version 1

Citation

Patrick Warin. Magnétorésistance et configuration de domaines. Matière Condensée [cond-mat]. Université Pierre et Marie Curie - Paris VI, 1999. Français. ⟨tel-00000860⟩

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