1. School of Physics, Sontheast University, Nanjing 211189, People's Republic of China
2. Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, People's Republic of China
3. School of Physics and Telecommunication Engineering, Zhoukou Normal University, Zhoukou 466001, China
4. York-Nanjing International Joint Center in Spintronics, Department of Electronics, The University of York, York YO10 5DD, United Kingdom