1. State Key Laboratory of Applied Organic Chemistry Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province College of Chemistry and Chemical Engineering Lanzhou University Lanzhou 730000 China
2. Key Laboratory of Magnetism and Magnetic Materials of Ministry of Education School of Physical Science and Technology Lanzhou University Lanzhou 730000 China
3. College of Science Henan Agricultural University Zhengzhou 450002 China
4. State Key Laboratory of Baiyunobo Rare Earth Resource Researches and Comprehensive Utilization Baotou Research Institute of Rare Earths Baotou 014030 China