1. Department of Quantum Matter, ADSM, Hiroshima University, Higashihiroshima, Hiroshima 739-8530, Japan
2. Department of Engineering Physics, Electronics and Mechanics, Graduate School of Engineering, Nagoya Institute of Technology, Nagoya 466-8555, Japan
3. Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan
4. Institute for Advanced Materials Research, Hiroshima University, Higashihiroshima, Hiroshima 739-8530, Japan
5. Cryogenics and Instrumental Analysis Division, N-BARD, Hiroshima University, Higashihiroshima, Hiroshima 739-8526, Japan