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Décalage d'échange et magnétorésistances dans des bicouches à base de ferrimagnétiques amorphes couplés par échange

Abstract : The study of exchange coupled amorphous ferrimagnetic/ferrimagnetic bilayers was made possible thanks to the use of complementary technics (magnetization, susceptibility, magnetoresitivity measurements, polarized neutrons reflectometry, X-Ray magnetic dichroism). As in the FeF2/Fe system, unusual exchange-bias properties have been observed in Gd40Fe60/Tb12Fe88 bilayer. Those properties could be explained, for low temperatures and low cooling fields, using a 1D spins chain model and considering that the TbFe magnetic configurations freeze as the sample is cooled down under a field. Variations of the exchange-bias and the magnetization shifts in function of the cooling field value could then be explained. However the role of the thermal activation and of GdFe magnetization reversals on the changes of the magnetic configuration inside the TbFe had to be taken in count in order to understand the evolutions of the coercivity and the training effects. The influence of lateral domains has also been studied. The presence of well-defined interface domain wall in the GdFe/TbFe or GdFe/GdFe systems allowed us to study domain wall magnetoresistance. For low field, the resistance variations can be fully understood in term of anisotropic magnetoresistance. However, for higher field, i.e. also for a thin domain wall, the amorphous materials intrinsic magnetoresistance must be used to explain our experimental results. Finally, we used these results to understand the magnetoresistance effects obtained in GdFe/GdFe/Cu/GdFe spin-valves.
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Contributor : Thomas Hauet <>
Submitted on : Wednesday, October 11, 2006 - 5:13:13 PM
Last modification on : Thursday, November 12, 2020 - 3:42:03 PM
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  • HAL Id : tel-01746613, version 2


Thomas Hauet. Décalage d'échange et magnétorésistances dans des bicouches à base de ferrimagnétiques amorphes couplés par échange. Matière Condensée [cond-mat]. Université Henri Poincaré - Nancy 1, 2006. Français. ⟨NNT : 2006NAN10067⟩. ⟨tel-01746613v2⟩



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