1. Advanced Electronics Research Laboratory, Hitachi Metals, Ltd., 5200 Mikajiri, Kumagaya, Saitama 360-0843
2. Department of Applied Physics, Graduate School of Engineering, Tohoku University, 04 Aoba-yama, Aoba-ku, Sendai 980-8579
3. Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577