1. Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577, Japan
2. Graduate School of Engineering, Tohoku University, Sendai 980-0845, Japan
3. WPI-Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
4. Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907, U.S.A.
5. Purdue Quantum Science and Engineering Institute, Purdue University, West Lafayette, IN 47907, U.S.A.
6. Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, U.S.A.
7. School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN 47907, U.S.A.
8. Center for Science and Innovation in Spintronics, Tohoku University, Sendai 980-8577, Japan
9. Center for Emergent Matter Science, RIKEN, Wako, Saitama 351-0198, Japan