1. Hakodate National College of Technology, 14-1 Tokura-cho, Hakodate, Hokkaido 042-8501
2. Department of Physics and Mathematics, Aoyama Gakuin University, 5-10-1 Fuchinobe, Sagamihara, Kanagawa 229-8558
3. Kyoto Sangyo University, Motoyama, Kamigamo, Kita-ku, Kyoto 603-8555
4. Multiferroics Project (MF), ERATO, Japan Science and Technology Agency (JST), c/o Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656