1. CAS 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. University of Chinese Academy of Sciences, Beijing 100049, P. R. China.
4. National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.