1. Department of Material Physics, Faculty of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531
2. Institute for Solid State Physics, The University of Tokyo, Tanashi, Tokyo 188-0002
3. Joint Research Center of Atom Technology (JRCAT), Tsukuba, Ibaraki 305-0046
4. Department of Applied Physics, Faculty of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656
5. Graduate School of Materials Science, Nara Institute of Science and Technology, Ikoma, Nara 630-0101