1. Key Laboratory of Magnetic Materials and Devices; Ningbo Institute of Materials Technology and Engineering; Chinese Academy of Sciences; Ningbo 315201 P. R. China
2. Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology; Ningbo Institute of Materials Technology and Engineering; Chinese Academy of Sciences; Ningbo 315201 P. R. China
3. Institute of Applied Chemistry; East China University of Science and Technology; Shanghai 200237 China