1. College of Science and Engineering, Kanazawa University, Kakuma-machi, Kanazawa-shi, Ishikawa 920-1192, Japan
2. Osaka Central Advanced Mathematical Institute (OCAMI), Osaka Metropolitan University, 3-3-138, Sugimoto, Osaka 558-8585, Japan
3. Taiyo Yuden Co., LTD. Tamamura Plant, 1796-1, Kawai, Tamamura-machi, Gunma 370-1196, Japan