Micro bobines à champ pulsé : applications aux champs forts et à la dynamique de renversement de l'aimantation à l'échelle de la nanoseconde par effet Kerr et Dichroïsme Circulaire Magnétique de rayons X

Abstract : In this thesis we have developed three techniques for the dynamic measurement of magnetisation reversal on the nanosecond time scale using micro coils as a source of pulsed field. The dynamic behaviour of several thin film magnetic systems was studied. With the time resolved X-rays Magnetic Circular Dichroism (XMCD) technique developed at the ESRF, one obtains the chemical selectivity in species as well as a temporal resolution of 100 ps. That enabled us to carry out studies on magnetisation reversal and dynamic coupling in spin valve and tunnel junction type structures. Under certain conditions of pulsed field the magnetisation reversal dynamics of the free layer (FeNi) is about one nanosecond. In these structures, depending on the thickness of the nonmagnetic layer, the dynamic coupling between the free and the hard layers can be very different from the static one. The Kerr/Faraday dynamic technique was shown to be effective for the dynamic study of thin films with strong perpendicular anisotropy due to the possibility of obtaining high magnetic fields (up to 10 T) associated with a high sensitivity (~2x10(+8) µB). With the time resolved Kerr/Faraday imaging technique we have studied the magnetisation reversal of a magnetic garnet following a field pulse. The processes involved in the reversal are easily identified by the time resolved image of the magnetic domains. With the micro coils developed in collaboration with the LETI, we showed the possibility of obtaining very strong magnetic fields (up to 50 T) at a very low cost compared with conventional high field installations. For the continuation of this work we consider the development of a dynamic technique of imaging with high spatial resolution (tens of nm) and chemical selectivity based on a PEEM microscope (Photoemission Electron Microscope).
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Theses
Condensed Matter. Université Joseph-Fourier - Grenoble I, 2001. French


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Submitted on : Wednesday, January 12, 2005 - 1:43:52 PM
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Marlio Bonfim. Micro bobines à champ pulsé : applications aux champs forts et à la dynamique de renversement de l'aimantation à l'échelle de la nanoseconde par effet Kerr et Dichroïsme Circulaire Magnétique de rayons X. Condensed Matter. Université Joseph-Fourier - Grenoble I, 2001. French. <tel-00008020>

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