Co_2MnSiを用いた強磁性トンネル接合における極高スピン分極率の実現

概要

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We fabricated Co_2MnSi/(Mg)/Al-O/CoFe MTJs using UHV magnetron sputtering. The interfacial chemical bond between Co_2MnSi and Al-0 was intensively optimized by changing plasma oxidation time for Al-O and by inserting a Mg layer. The Mg inserted layer between Co_2MnSi 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 Co_2MnSi 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 Co_2MnSi. As a result, we found that an L2_1-ordering state is not necessary to achieve high spin-polarization for Co_2MnSi in MTJs.
社団法人日本磁気学会の論文
2007-07-01