N. Ishimatsu,1,* T. Shichijo,1 Y. Matsushima,1 H. Maruyama,1 Y. Matsuura,2 T. Tsumuraya,3 T. Shishidou,2 T. Oguchi,4 N. Kawamura,5 M. Mizumaki,5 T. Matsuoka,6 and K. Takemura7 1Department of Physics, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashihiroshima, Hiroshima 739-8526, Japan 2Graduate School of Advanced Sciences of Matter (ADSM), Hiroshima University, 1-3-1 Kagamiyama, Higashihiroshima, Hiroshima 739-8530, Japan 3RIKEN Advanced Science Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan 4The Institute of Scientific and Industrial Research (ISIR), Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan 5Japan Synchrotron Radiation Research Institute (JASRI), SPring-8, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan 6KYOKUGEN, Center for Quantum Science and Technology under Extreme Conditions, Osaka University, Osaka 560-8531, Japan 7National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan (Received 30 December 2011; revised manuscript received 24 August 2012; published 24 September 2012)