1. Department of Materials Science, Tohoku University, Sendai 980-8579, Japan
2. Center for Science and Innovation in Spintronics, Tohoku University, Sendai 980-8577, Japan
3. Department of Electrical Engineering and Information Systems, The University of Tokyo, Bunkyo, Tokyo 113-8656, Japan
4. Institute of Engineering Innovation, The University of Tokyo, Bunkyo, Tokyo 113-8656, Japan
5. PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
6. Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
7. Division for the Establishment of Frontier Sciences, Tohoku University, Sendai 980-8577, Japan
8. Center for Spintronics Research Network (CSRN), The University of Tokyo, Bunkyo, Tokyo 113-8656, Japan