1. National Institute for Materials Science 1‐2‐1 Sengen, Tsukuba Ibaraki 305‐0047 Japan
2. Division of Mechanical and Space EngineeringHokkaido University Sapporo Hokkaido 060‐8628 Japan
3. Japan Synchrotron Radiation Research Institute/Spring‐8 Sayo Hyogo 679‐5198 Japan