1. Guangdong Provincial Key Laboratory of Optical Information Materials and Technology & Institute for Advanced Materials South China Academy of Advanced Optoelectronics South China Normal University Guangzhou 510006 P. R. China
2. School of Materials Science and Engineering Dongguan University of Technology Dongguan 523808 P. R. China
3. Fert Beijing Institute School of Integrated Circuit Science and Engineering Beihang University Beijing 100191 P. R. China
4. Department of Materials Physics and Chemistry University of Science and Technology Beijing Beijing 100083 P. R. China
5. Department of Electrical and Computer Engineering Shinshu University 4‐17‐1 Wakasato Nagano 380–8553 Japan
6. Ultrafast Electron Microscopy Laboratory School of Physics Nankai University Tianjin 300071 P. R. China
7. School of Science and Engineering The Chinese University of Hong Kong Shenzhen Guangdong 518172 P. R. China
8. Laboratory of Solid State Microstructures and Innovation Center of Advanced Microstructures Nanjing University Nanjing 211102 P. R. China