1. Materials
Sciences Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
2. Division
of Applied Chemistry and Biotechnology, Graduate School of Engineering, Chiba University, 1-33
Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
3. Department
of Physics, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan