1. National Institute for Research in Inorganic Materials, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan, Ishihara Sangyo Kaisha, 1 Ishiharacho, Yokkaichi, Mie 594-0084, Japan, and Solid State Division, Oak Ridge National Laboratory, Oak Ridge, Tennesee 37831-6393