1. Key Laboratory of Materials PhysicsInstitute of Solid State PhysicsChinese Academy of Sciences Hefei 230031 P. R. China
2. University of Science and Technology of China Hefei 230026 P. R. China
3. High Magnetic Field LaboratoryChinese Academy of Sciences Hefei 230031 P. R. China
4. Key Laboratory of New Processing Technology for Nonferrous Metals and MaterialsMinistry of EducationGuilin University of Technology Guilin 541004 P. R. China
5. Collaborative Innovation Center of Advanced MicrostructuresNanjing University Nanjing 210093 P. R. China