Extremely large spin-polarization in Co2MnSi based magnetic tunnel junctions

Authors:
  • YSY. Sakuraba
    Y. Sakuraba
  • MHM. Hattori
    M. Hattori
  • MOM. Oogane
    M. Oogane
  • YAY. Ando
    Y. Ando
  • ASA. Sakuma
    A. Sakuma
  • NTN. D. Telling
    N. D. Telling
  • PKP. Keatley
    P. Keatley
  • EAE. Arenholz
    E. Arenholz
  • RHR. J. Hicken
    R. J. Hicken
  • TMT. Miyazaki
    T. Miyazaki
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Abstract
We fabricated Co2MnSi/(Mg)/Al-O/CoFe MTJs using UHV magnetron sputtering. The interfacial chemical bond between Co2MnSi and Al-O was intensively optimized by changing plasma oxidation time for Al-O and by inserting a Mg layer. The Mg inserted layer between Co2MnSi and Al-O effectively suppressed the generation of interfacial magnetic impurities. Finally, we successfully observed a giant TMR ratio of 203% at 2 K in the MTJ with a 1.0 nm-Mg layer inserted. The spin-polarization for Co2MnSi estimated from this TMR ratio was 0.97-1.00, which indicated that an almost perfect spin-polarized state was achieved. We also investigated the relationship between the TMR ratio and the site-ordering level of Co2MnSi. As a result, we found that an L21-ordering state is not necessary to achieve high spin-polarization for Co2MnSi in MTJs.

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