1. Department of Physics and IPIT, Chonbuk National University, Jeonju 561-756, South Korea
2. Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
3. Department of Geophysics, National University of Mongolia, Ulaanbaatar 210646, Mongolia
4. Department of Physics, Sungkyunkwan University, Suwon 440-746, South Korea
5. Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506, USA
6. Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba 277-8561, Japan
7. Department of Applied Physics, Stanford University, Stanford, California 94305-4045, USA