1. Department of Material Science, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki, 305-0003, Japan
2. Tsukuba Magnet Laboratory, National Institute for Materials Science (NIMS) Sakura 3-13, Tsukuba, Ibaraki, 305-003, Japan
3. Photon Factory and Condensed Matter Research Center, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki, 305-801, Japan