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Anisotropie Magnétique et Hystérésis du Cobalt à l'Échelle du Plan Atomique: Théorie et Expérience

Abstract : This thesis presents experimental and theoretical studies of the magnetic properties of epitaxial cobalt ultrathin films on polycrystalline gold substrates. The hysteresis cycle measurements confirm the existence (previously evidenced by means of ferromagnatic resonance) of a strong interface magnetic anisotropy opposed to the demagnetizing field, and giving, for cobalt thicknesses lower than 6 atomic layers, to a switching of the easy axis perpendicular to the film plane. I have als evidenced two new phenomena: at low temperature, the corecive field increases strongly at low thicknesses; at room temperature, there is an important magnetic aftereffect. I have interpreted these phenomena by means of a model of Bloch wall motion, emphasizing the role of the interface roughness. I have investigated theoretically, by means of elecronic structure calculations within the tight-binding approximation, the magnetic anisotroy of iron, cobalt, and nickel monoatomic layers. These calculations contributent to a better understanding of this phenomenon. In addition, the study of the orbital momentum led me to the prediction of of an orginal effet in these ultrathin films: an anisotropy of the magnetization, of the order of 0.1 Bohr magneton, considerably larger than the one of bulk materials. Finally, I have investigated, by means of phnomenological models the influence of defects (roughness, interfacial strains) on the magnetic anisotropy.
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Contributor : Patrick Bruno <>
Submitted on : Monday, May 19, 2003 - 4:23:43 PM
Last modification on : Wednesday, October 14, 2020 - 3:57:03 AM
Long-term archiving on: : Tuesday, September 7, 2010 - 4:32:58 PM


  • HAL Id : tel-00002846, version 1



Patrick Bruno. Anisotropie Magnétique et Hystérésis du Cobalt à l'Échelle du Plan Atomique: Théorie et Expérience. Matière Condensée [cond-mat]. Université Paris Sud - Paris XI, 1989. Français. ⟨tel-00002846⟩



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