1. Key Laboratory of Magnetic Materials and Devices & Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China
2. MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
3. National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
4. Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China