1. Department of Materials Science and Engineering, Tokyo Institute of Technology, Yokohama 226-8502, Japan
2. Department of Mathematics and Physics, Kanagawa University, Hiratsuka, Kanagawa 259-1293, Japan
3. Department of Condensed Matter Physics, Tokyo Institute of Technology, Meguro, Tokyo 152-8551, Japan
4. Division of General Education, Ashikaga Institute of Technology, Ashikaga, Tochigi 326-8558, Japan
5. Graduate School of Material Science, University of Hyogo, Kamigori, Hyogo 678-1297, Japan
6. Department of Physics, Keio University, Yokohama 223-8522, Japan