1. Department of Materials Science and Technology, Niigata University, Niigata 950-2181, Japan
2. Faculty of Science, University of the Ryukyus, Nishihara, Okinawa 903-0213, Japan
3. Faculty of Environmental Design, Kanazawa University, Kanazawa 920-1192, Japan
4. Department of Physics, Kyushu University, Fukuoka 812-8581, Japan
5. Department of Education and Creation Engineering, Kurume Institute of Technology, Kurume, Fukuoka 830-0052, Japan