Affiliation: | 1. University of Tokyo, Institute of Physics, Komaba 3-8-1, Meguro-ku, Tokyo 153, Japan;2. Department of Physics, Tokyo Institute of Technology, Tokyo 152-8551, Japan;3. Department of Physics, Keio University, Hiyoshi, Yokohama, Kanagawa 223-8521, Japan;4. Department of Physics, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan |