1. Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043
2. Institute for Materials Research, Tohoku University, Sendai 980-8577
3. Central Workshop, Osaka University, Toyonaka, Osaka 560-0043
4. Low Temperature Center, Osaka University, Toyonaka, Osaka 560-0043
5. Tata Institute of Fundamental Research, Bombay, India