1. Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
2. Department of Physics, Chung-Ang University, Seoul 06974, South Korea
3. Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
4. Department of Physics, Pusan National University, Busan 46241, Korea
5. Laboratory for Advanced Fibers, Empa, Swiss Federal Laboratories for Materials Science and Technology, Lerchenfeldstrasse 5, 9014 St. Gallen, Switzerland
6. Department of Physics, Northern Illinois University, DeKalb, Illinois 60115, USA