1. College of Physics and Information Engineering, Hebei Normal University, Shijiazhuang 050024, P. R. China
2. Hebei Advanced Thin Films Laboratory, Shijiazhuang 050024, P. R. China
3. Institute of Applied Physics and Computational Mathematics, P. O. Box 8009, Beijing 100088, P. R. China
4. Scientific and Technical Department, Hulunbuir University, Hulunbuir 021008, P. R. China
5. School of Sciences, Hebei University of Science and Technology, Shijiazhuang 050018, P. R. China