1. National High Magnetic Field Laboratory, Tallahassee, FL 83810, U.S.A.
2. MPA-NHMFL, Los Alamos National Laboratory, Los Alamos, NM 87545, U.S.A.
3. Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503
4. Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37931, U.S.A.