1. College of Physics and Electronic Information, Shanxi Normal University, Linfen 041004, China
2. Research Institute of Materials Science of Shanxi Normal University and Collaborative Innovation Center for Shanxi Advanced Permanent Magnetic Materials and Technology, Linfen 041004, China
3. State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
4. School of Chemistry and Materials Science of Shanxi Normal University and Key Laboratory of Magnetic Molecules and Magnetic Information Materials of Ministry of Education, Linfen 041004, China