1. Japan Fine Ceramics Center 1 , 2-4-1 Mutsuno, Atsuta, Nagoya 456-8587, Japan
2. Graduate School of Science, University of Hyogo 2 , 3-2-1, Koto, Kamigori-cho, Ako-gun, Hyogo 678-1297, Japan
3. High Energy Accelerator Research Organization (KEK) 3 , 1-1 Oho, Tsukuba 305-0801, Japan
4. Novel Crystal Technology, Inc. 4 , Sayama 350-1328, Japan