1. School of Materials Science and Engineering Beijing Key Laboratory for Magnetoelectric Materials and Devices Beijing Innovation Centre for Engineering Science and Advanced Technology Peking University Beijing 100871 China
2. State Key Laboratory for Artificial Microstructure and Mesoscopic Physics School of Physics Peking University Beijing 100871 China
3. State Key Laboratory of Superlattices and Microstructures Institute of Semiconductors Chinese Academy of Sciences Beijing 100083 China
4. Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China
5. Institute of Physics Chinese Academy of Sciences Beijing 100190 China