Current-induced spin polarization on metal surfaces observed by spin-polarized positron beam

スピン偏極陽電子ビームを用いた金属表面電流誘起のスピン偏極の研究

Zhang, H.; 山本 春也; Li, H.; 深谷 有喜   ; 前川 雅樹; 河裾 厚男; 関 剛斎*; 齊藤 英治*; 高梨 弘毅*

Zhang, H.; Yamamoto, Shunya; Li, H.; Fukaya, Yuki; Maekawa, Masaki; Kawasuso, Atsuo; Seki, Takeshi*; Saito, Eiji*; Takanashi, Koki*

The current-induced outermost (0.1 to 0.2 nm) surface spin polarization of W, Ta, Pt, Pd, Au and Cu nano-scaled films has been observed by using the spin-polarized positron beam. The surface spin polarization of Pt (25 nm) and Pd (25 nm) films is positive and has a giant value as high as 10% at a charge current density of 2E5 A/cmE2. As for Ta and W, the surface spin polarization has a negative sign and the magnitude is rather larger (normalized to a current density of 1E5 A/cmE2). On Au and Cu outermost surfaces, spin polarizations are not detected. The material dependence of surface spin polarization on these six metals is similar to that of spin Hall angle, clarifies that the giant surface spin polarization on transition metal thin films is most probably induced by the spin-orbit interaction.