1. a Sumitomo Metal Mining Co., Central Research Lab , Ichikawa, Chiba , 272 , Japan
2. b Naval Postgraduate School, Materials Science Group , Monterey , CA , 93943 , USA
3. c National Defence Academy, Department of Physics , Yokosuka , 239 , Japan
4. d Monterey Institute of Advanced Studies , PO Box 975, Monterey , CA , 93943 , USA