[1] Tohoku Univ, Inst Mat Res, Sendai, Miyagi 9808577, Japan
[2] Japan Sci & Technol Agcy, PRESTO, Saitama 3320012, Japan
[3] Tohoku Univ, WPI Adv Inst Mat Res, Sendai, Miyagi 9808577, Japan
[4] Japan Sci & Technol Agcy, ERATO, Spin Quantum Rectificat Project, Sendai, Miyagi 9808577, Japan
[5] Japan Atom Energy Agcy, Adv Sci Res Ctr, Tokai, Ibaraki 3191195, Japan