1. Department of Applied Physics and Physico‐Informatics Keio University Yokohama 223‐8522 Japan
2. Laboratory for Materials and Structures Tokyo Institute of Technology Yokohama 226‐8503 Japan
3. Keio Institute of Pure and Applied Sciences Keio University Yokohama 223‐8522 Japan
4. Center for Spintronics Research Network Keio University Yokohama 223‐8522 Japan