1. RIKEN Center for Emergent Matter Science Wako 3510198 Japan
2. Center for Spintronics Korea Institute of Science and Technology Seoul 02792 Korea
3. KU‐KIST Graduate School of Converging Science and Technology Korea University Seoul 02841 Korea
4. Department of Electrical and Computer Engineering Shinshu University Nagano 3808553 Japan
5. National Institute for Materials Science Tsukuba Ibaraki 3050044 Japan
6. IBM T. J. Watson Research Center New York NY 10598 USA