1. WPI Advanced Institute for Materials Research (AIMR), Tohoku University, Sendai 980-8577, Japan
2. Center for Science and Innovation in Spintronics (CSIS), Tohoku University, Sendai 980-8577, Japan
3. Department of Physics and Astronomy, Purdue Quantum Science and Engineering Institute, Purdue University, West Lafayette, Indiana 47907, USA
4. Frontier Research Institute for Interdisciplinary Sciences (FRIS), Tohoku University, Sendai 980-8578, Japan
5. Center for Spintronics Research Network (CSRN), Tohoku University, Sendai 980-8577, Japan
6. Graduate School of Environmental Studies, Tohoku University, Sendai 980-8579, Japan
7. WPI-International Center for Materials Nanoarchitectonics (MANA), National Institute for Material Science, Tsukuba 305-0044, Japan
8. School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA