1. Department of Physics Tokyo Metropolitan University Tokyo 192–0397 Japan
2. Nanomaterials Research Institute National Institute of Advanced Industrial Science and Technology (AIST) Tsukuba 305–8565 Japan
3. Department of Electronic Engineering Tohoku University 980–8579 Sendai Japan
4. Advanced Institute for Materials Research (AIMR) Tohoku University Sendai 980–8577 Japan
5. KOKUSAI ELECTRIC CORP. Toyama 939–2393 Japan
6. The Institute of Scientific and Industrial Research Osaka University Osaka 567‐0047 Japan