1. Materials Sciences Research Center, Japan Atomic Energy Agency, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
2. Center for Spintronics Research Network, Graduate School of Engineering, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
3. Department of Electronic Engineering and Information Systems, The University of Tokyo, Hongo, Bunkyo-ku,
Tokyo 113-8656, Japan
4. Department of Electrical and Electronic Engineering, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8550 Japan
5. Department of Physics, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-Ku, Kyoto 603-8555, Japan
6. Department of Physics, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan