1. Department of Materials Science and Engineering, School of Materials and Chemical Technology, Tokyo Institute of Technology, 4259 Nagatsuta-Cho Midori-Ku, Yokohama, Kanagawa 226-8502, Japan
2. Research Institute for Advanced Materials and Devices, Kyocera Corporation, 3-5-3 Hikaridai, Seika-Cho, Soraku-gun, Kyoto 619-0237, Japan
3. The Institute for Solid State Physics, the University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba, 277-0882, Japan