Journal of Magnetics

The Korean Magnetics Society (한국자기학회)
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Magnetization Process in Vortex-imprinted Ni80Fe20/Ir20Mn80 Square Elements

  • Xu, H. (Dept. of Physics and Astronomy, University of Victoria) ;
  • Kolthammer, J. (Dept. of Physics and Astronomy, University of Victoria) ;
  • Rudge, J. (Dept. of Physics and Astronomy, University of Victoria) ;
  • Girgis, E. (Dept. of Physics and Astronomy, University of Victoria) ;
  • Choi, B.C. (Dept. of Physics and Astronomy, University of Victoria) ;
  • Hong, Y.K. (Dept. of Electrical and Computer Engineering, The University of Alabama) ;
  • Abo, G. (Dept. of Electrical and Computer Engineering, The University of Alabama) ;
  • Speliotis, Th. (Institute of Materials Science, NCSR) ;
  • Niarchos, D. (Institute of Materials Science, NCSR)
  • Received : 2011.02.09
  • Accepted : 2011.04.29
  • Published : 2011.06.30
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Abstract

The vortex-driven magnetization process of micron-sized, exchange-coupled square elements with composition of $Ni_{80}Fe_{20}$ (12 nm)/$Ir_{20}Mn_{80}$ (5 nm) is investigated. The exchange-bias is introduced by field-cooling through the blocking temperature (TB) of the system, whereby Landau-shaped vortex states of the $Ni_{80}Fe_{20}$ layer are imprinted into the $Ir_{20}Mn_{80}$. In the case of zero-field cooling, the exchange-coupling at the ferromagnetic/antiferromagnetic interface significantly enhances the vortex stability by increasing the nucleation and annihilation fields, while reducing coercivity and remanence. For the field-cooled elements, the hysteresis loops are shifted along the cooling field axis. The loop shift is attributed to the imprinting of displaced vortex state of $Ni_{80}Fe_{20}$ into $Ir_{20}Mn_{80}$, which leads to asymmetric effective local pinning fields at the interface. The asymmetry of the hysteresis loop and the strength of the exchange-bias field can be tuned by varying the strength of cooling field. Micromagnetic modeling reproduces the experimentally observed vortex-driven magnetization process if the local pinning fields induced by exchange-coupling of the ferromagnetic and antiferromagnetic layers are taken into account.

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References

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  1. Magnetization Dynamics in Vortex-Imprinted Ni$_{80}$ Fe$_{20}$/Ir$_{20}$Mn$_{80}$ Square Elements vol.3, pp.1949-3088, 2012, https://doi.org/10.1109/LMAG.2012.2207882