1. T. Kimura, Y. Tomioka, H. Kuwahara, A. Asamitsu, M. Tamura, Joint Research Center for Atom Technology (JRCAT), Tsukuba, 305, Japan.
2. Y. Tokura, JRCAT, Tsukuba, 305, Japan, and Department of Applied Physics, University of Tokyo, Tokyo 113, Japan.