1. School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006, China
2. National Engineering Research Center for Rare Earth Materials, General Research Institute for Nonferrous Metals, Grirem Advanced Materials Co., Ltd., Beijing 100088, China
3. School of Physics and Electronic Engineering, Anqing Normal University, Anqing 246133, China
4. Department of Physics, University of Science and Technology of China, Hefei 230026, China
5. State Key Laboratory of Nonferrous Metals and Processes, General Research Institute for Nonferrous Metals, Beijing 100088, China
6. Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China