1. Department of Electrical Engineering and Information Systems, Graduate School of Engineering, The University of Tokyo 1 , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
2. School of Materials Science and Engineering, Beijing Institute of Technology 2 , Beijing 100081, China
3. Center for Spintronics Research Network, Graduate School of Engineering, The University of Tokyo 3 , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
4. Institute for Nano Quantum Information Electronics, The University of Tokyo 4 , 4-6-1, Komaba, Meguro-ku, Tokyo 153-8505, Japan