1. Department of Applied Chemistry, Tokyo Metropolitan University, 1-1 Minami-ohsawa, Hachioji, Tokyo 192-0397, Japan, Tsukuba Magnet Laboratory, National Institute for Materials Science, 3-13 Sakura, Tsukuba, Ibaraki 305-0003, Japan, and Research and Development Center, Polymatech Company, Limited, 5-10-5 Tabata, Kita, Tokyo 114-0014, Japan