1. Department of Physics, Niigata University, Niigata 950-2181, Japan
2. Low Temperature Center, Osaka University, Toyonaka, Osaka 560-0043, Japan
3. Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan
4. Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313, Japan
5. Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
6. Center for Advanced High Magnetic Field Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
7. Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan