1. Department of Physics, Saga University, Saga 840-8502
2. Kyushu National Industrial Research Institute, Saga 841-0052
3. HVEM Lab., Kyushu University, Fukuoka 812-8581
4. Department of Physics, Kyushu University, Fukuoka 812-8581
5. Center for New Materials, Japan Advanced Institute of Science and Technology, Ishikawa, 923-1292