1. Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313, Japan
2. Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
3. Department of Physics, Faculty of Science, Niigata University, Niigata 950-2181, Japan
4. Low Temperature Center, Osaka University, Toyonaka, Osaka 560-0043, Japan
5. Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
6. Laboratoire National des Champs Magnétiques Intenses—Grenoble, CNRS, UJF, BP166, 38042 Grenoble Cedex 9, France
7. Department of Physics, College of Humanities and Sciences, Nihon University, Setagaya, Tokyo 156-8550, Japan
8. Department of Physics and Earth Sciences, Faculty of Science, University of The Ryukyus, Nishihara, Okinawa 903-0213, Japan