1. Fert Beijing Institute, MIIT Key Laboratory of Spintronics, School of Integrated Circuit Science and Engineering, Beihang University 1 , Beijing 100191, China
2. State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences 2 , Beijing 100083, China
3. National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University 3 , Nanjing 210093, China