1. Department of Material Science, University of Hyogo, Kamigori, Hyogo 678-1297, Japan
2. Synchrotron Radiation Research Center, National Institutes for Quantum Science and Technology, Sayo, Hyogo 679-5148, Japan
3. Center for Liberal Arts and Sciences, Sanyo-Onoda City University, Sanyo-Onoda, Yamaguchi 756-0884, Japan