Institution: | a Research Institute of Superconductivity, Kyushu University, 6-10-1 Hakozaki, Higashi-Ku, Fukuoka 812-8581, Japan b Kyushu Institute of Technology, 680-4 Kawazu, Iizuka 820-8502, Japan c Sumitomo Electric Industries, 1-1-3 Shimaya, Konohana-Ku, Osaka 554-0024, Japan |