1. Key Laboratory for Magnetism and Magnetic Materials of MOE; Key Laboratory of Special Function Materials and Structure Design of MOE; Lanzhou University; Lanzhou 730000 P. R. China
2. Department of Materials Science and Engineering; National University of Singapore; 9 Engineering Drive 1 Singapore 117575 Singapore
3. Lanzhou Jinchuan Advanced Materials Technology Co., Ltd.; Lanzhou 730000 P. R. China
4. The Research Center of Biomedical Nanotechnology; Lanzhou University; Lanzhou 730000 P. R. China