1. Center for Oxide Nanocrystalline Materials and School of Chemical and Biological Engineering, Seoul National University, Seoul 151-744, Korea, Pacific Northwest National Laboratory, Richland, Washington 99352, Department of Physics and Institute of Basic Science, Sungkyunkwan University, Suwon 440-746, Korea, and Department of Chemical Engineering, Chungbuk National University, Cheongju 360-763, Korea