1. Department of Quantum Matter, ADSM, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8530
2. Department of Applied Physics, National Defense Academy, Yokosuka, Kanagawa 239-8686
3. Center for Low Temperature Science, Tohoku University, Sendai 980-8578
4. Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581
5. Materials Science Center, N-BARD, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8530