1. Department of Physics, Tohoku University, Aramaki Aoba, Sendai 980-77
2. Department of Physics, Kobe University, Rokkoudai, Nada, Kobe 657
3. Institute of Inorganic Synthesis, Faculty of Engineering, Yamanashi University, Miyamae-cho 7, Kofu 400
4. Daresbury Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX, United Kingdom