1. Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503
2. Department of Physics, Faculty of Science, Shinshu University, 3-1-1 Asahi, Matsumoto 390-8621
3. Department of Electrical Engineering, College of Science and Engineering, Meisei University, 2-1-1 Hodokubo, Hino 191-8506