1. Center for Magnetic Materials and DevicesCollege of Physics and Electronic Engineering Qujing Normal University Qujing 655011 China
2. Key Laboratory for Advanced Functional and Low Dimensional Materials of Yunnan Higher Education Institute Qujing Normal University Qujing 655011 China
3. Key Laboratory of Materials Physics Institute of Solid State PhysicsChinese Academy of Sciences P.O. Box 1129 Hefei 230031 P. R. China