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Excitations magnétiques hautes fréquences dans des films minces à aimantation non uniforme

Abstract : This report addresses the study of small amplitude magnetic excitations in thin films with nonuniform magnetization distributions in the high-frequency range, typically between a few tens of MHz and a few tens of GHz. The ideal case of magnetic films possessing a perpendicular anisotropy and supporting an equilibrium magnetization configuration corresponding to parallel and periodic stripes is investigated in detail. For high values of the perpendicular anisotropy, the theoretical dynamic susceptibility spectra computed using analytical models and then by means of 2D dynamic micromagnetic simulations reveal several excitations localized either within the magnetic domains or within the magnetic domain walls. These results were satisfactorily compared with those deduced from ferromagnetic resonance measurements performed on single-crystal ferrimagnetic garnet films. However, the experimental linewidths of domain wall excitations exceed those computed using the Gilbert dissipative term. For low values of the perpendicular anisotropy, the theoretical dynamic susceptibility spectra present multiple excitations due to the highly heteregeneous equilibrium magnetization configuration of weak stripe-type. Modal analyses performed from the dynamic micromagnetic simulations indicate the existence of surface and volume modes localized in different spin regions of thin films. The influence of different parameters (perpendicular anisotropy, film thickness, static magnetic field) on the main features of spectra (number of resonances, resonance frequencies, intensities, and linewidths) is then investigated. These dynamic micromagnetic simulations allow to interpret some complex experimental dynamic permeabilty spectra measured on amorphous ferromagnetic films. Some outlooks concerning the small amplitude spin dynamics in different magnetic objects are then presented.
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Habilitation à diriger des recherches
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https://tel.archives-ouvertes.fr/tel-00003276
Contributor : Nicolas Vukadinovic <>
Submitted on : Thursday, August 28, 2003 - 1:30:49 PM
Last modification on : Thursday, August 28, 2003 - 1:30:49 PM
Long-term archiving on: : Tuesday, September 7, 2010 - 4:33:01 PM

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  • HAL Id : tel-00003276, version 1

Citation

Nicolas Vukadinovic. Excitations magnétiques hautes fréquences dans des films minces à aimantation non uniforme. Matière Condensée [cond-mat]. Université Paris Sud - Paris XI, 2003. ⟨tel-00003276⟩

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