1. Faculty of Materials Science and Chemistry China University of Geosciences Wuhan Hubei 430074 P. R. China
2. State Key Laboratory of Rare Earth Resource Utilization Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun Jilin 130022 P. R. China
3. Department of Applied Physics The Hong Kong Polytechnic University Hong Kong 999077 P. R. China
4. Zhejiang Institute China University of Geosciences Hangzhou 311305 P. R. China