1. School of Material ChemistryNingbo University Ningbo Zhejiang 315201 P. R. China
2. CAS Key Laboratory of Magnetic Materials and DevicesNingbo Institute of Materials Technology and EngineeringChinese Academy of Sciences Ningbo 315201 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. College of Materials Science and Opto-Electronic TechnologySchool of Future TechnologyUniversity of Chinese Academy of Sciences Beijing 100049 P. R. China
5. College of Information EngineeringNanjing University of Finance and Economics Nanjing 210046 P. R. China