1. Jiangsu Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing UniversityNanjing 210093P.R. China
2. Department of Electronic Engineering, Royal Holloway University of LondonEgham TW20 0EXUK
3. Department of Electronic Engineering, York‐Nanjing International Center of Spintronics (YNICS), The University of YorkYork YO10 3DDUK