1. Department of Mechanical Engineering, Faculty of Engineering and Resource Science, Akita University, Akita 010-8502
2. Department of Physics, Facultu of Science, Okayama University, Okayama 700-8530
3. High Field Laboratory for Superconducting Materials, Institute for Materials Research, Tohoku University, Sendai 980-8577
4. Physics Department, Graduated School of Science, Kyushu University, Fukuoka 812-8581