1. Toyota Central R&D Labs., Inc., Nagakute 480-1192, Japan
2. Graduate School of Integrated Science and Technology, Shizuoka University, Hamamatsu 432-8561, Japan
3. Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577, Japan
4. Center for Spintronics Research Network (CSRN), Osaka University, Osaka 560-8531, Japan
5. Department of Electronic Engineering, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan
6. Center for Science and Innovation in Spintronics (Core Research Cluster), Organization of Advanced Studies, Tohoku University, Sendai 980-8577, Japan