1. School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, P. R. China
2. National Institute of Metrology, Beijing 100029, P. R. China
3. Department of Physics, Capital Normal University, Beijing 100048, P. R. China
4. Beijing Institute of Aerospace Testing Technology, China Aerospace Science and Technology Corporation, Beijing 100074, P. R. China
5. State key laboratory for Magnetism, Institute of Physics, Chinese Academy of Sciences & University of Chinese Academy of Sciences, Beijing 100190, P. R. China