1. School of Materials Science and Engineering, Zhengzhou University, 450001Zhengzhou, Henan, P. R. China
2. State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, 430071Wuhan, P. R. China
3. University of Chinese Academy of Sciences, 101408Beijing, P. R. China