1. State Key Laboratory for Mesoscopic Physics School of Physics Peking University Beijing 100871 P. R. China
2. Department of Micro‐nano Fabrication Technology Institute of Electrical Engineering Chinese Academy of Sciences Beijing 100190 P. R. China
3. School of Materials Engineering Purdue University West Lafayette IN 47906 USA
4. Collaborative Innovation Center of Quantum Matter Beijing 100871 P. R. China
5. Beijing Key Laboratory for Magnetoelectric Materials and Devices Beijing 100871 P. R. China