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. Nano Science and Technology Institute University of Science and Technology of China Suzhou 215123 P. R. China
4. Laboratoire CRISMAT CNRS UMR 6508 ENSICAEN Normandie Université, 6 Bd Maréchal Juin, F‐14050 Caen Cedex 4 France
5. College of Materials Science and Opto‐Electronic Technology University of Chinese Academy of Sciences Beijing 100049 P. R. China