1. Wuhan National High Magnetic Field Center and Department of Physics Huazhong University of Science and Technology Wuhan 430074 P. R. China
2. State Key Laboratory of Materials Processing and Die & Mould Technology School of Materials Science and Engineering Huazhong University of Science and Technology Wuhan 430074 P. R. China
3. School of Elementary Education Wuhan City Polytechnic College Wuhan 430074 P. R. China