1. B.Verkin Institute for Low Temperature Physics and Engineering, NAS of Ukraine, 47 Ave., 310164, Kharkiv, Ukraine
2. Max-Planck-lnstitut fuer Chemische Physik fester Stoffe, Bayreuther Str. 40, Haus 16, D-01187, Dresden, Germany
3. Graduate School of Science, Osaka University, Toyonaka 560, Japan
4. Advanced Science Research Center, Atomic Energy Research Institute of Japan, Tokai, Ibaraki 319-11, Japan