1. CAS Key Laboratory of Magnetic Materials and DevicesNingbo Institute of Materials Technology and EngineeringChinese Academy of Sciences Ningbo 315201 P. R. China
2. College of Materials Science and Opto‐Electronic TechnologyUniversity of Chinese Academy of Sciences Beijing 100049 P. R. China
3. Zhejiang Province Key Laboratory of Magnetic Materials and Application TechnologyNingbo Institute of Materials Technology and EngineeringChinese Academy of Sciences Ningbo 315201 P. R. China
4. State Key Laboratory of Fluid Power and Mechatronic SystemKey Laboratory of Soft Machines and Smart Devices of Zhejiang ProvinceDepartment of Engineering MechanicsZhejiang University Hangzhou 310027 China
5. College of Information EngineeringNanjing University of Finance and Economics Nanjing 210046 China