1. WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
2. Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577, Japan
3. Department of Physics, Mindanao State University-Iligan Institute of Technology, Iligan City 9200, Philippines
4. Center for Science and Innovation in Spintronics, Tohoku University, Sendai 980-8577, Japan
5. Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
6. Center for Innovative Integrated Electronic Systems, Tohoku University, Sendai 980-0845, Japan