1. H. Kuwahara, Y. Tomioka, Y. Moritomo, A. Asamitsu, M. Kasai, R. Kumai, Joint Research Center for Atom Technology, Tsukuba 305, Japan.
2. Y. Tokura, Joint Research Center for Atom Technology, Tsukuba 305, and Department of Applied Physics, University of Tokyo, Tokyo 113, Japan.