191st Special MMU seminar


A first-principles study on spin-dependent transport in magnetic junctions with half-metallic Heusler alloys

Prof. Yoshio Miura
Kyoto Institute of Technology
Date: December 19th (Thu), 2013
Time: 15:00 - 16:00
Place: 8F medium seminar room, Sengen
Recently, several Co-based Heusler compounds (Co2YZ), a class of half-metallic ferromagnets (HMFs), have been applied as ferromagnetic electrodes in tunnel magnetoresitive (TMR) devices and current perpendicular-to-plane giant magnetoresistive (CPP-GMR) devices to enhance the MR properties. In TMR, the most important problem in experiments is large temperature dependence of TMR ratio in magnetic tunnel junctions (MTJs) with Co2YZ. We showed that reduction of TMR ratio at room temperature in Co2MnSi/MgO/Co2MnSi MTJ can be attributed to a spin-flip scattering of tunneling electrons with in-plane wave vecter k//=0 at interfacial regions caused by the thermal fluctuation of interfacial Co spin-moments[1]. In CPP-GMR, HMFs are more essential to obtain large MR, because electrons with k//0 can contribute to the current. We found that Ag, Au, and Al spacers in CPP-GMR devices with Co2YZ will provide the small interface resistance in parallel magnetization because of the matching of the Fermi surface with Co2YZ, providing the large interfacial spin-asymmetry coefficient. Finally, we discuss the origin of perpendicular magneto-crystalline anisotropy (MCA) of Co2FeAl/MgO interface and demonstrate the electrical modulation of the interfacial MCA.

[1] Y. Miura, et al., Phys. Rev. B 83, 214411 (2011).
[2] Y. Miura, et al., Phys. Rev. B 84, 134432 (2011).