1. National Synchrotron Radiation Laboratory University of Science and Technology of China Hefei Anhui 230029 China
2. Department of Physics University of California at Berkeley Berkeley CA 94720 USA
3. Institute of Physical Science and Information Technology Anhui University Hefei Anhui 230601 China
4. NCEM Lawrence Berkeley National Laboratory Berkeley CA 94720 USA
5. Department of Physics Kyung Hee University Seoul 02447 Republic of Korea
6. Center for Spintronics Korea Institute of Science and Technology Seoul 02792 Republic of Korea
7. Korea Research Institute of Standards and Science Yuseong Daejeon 305–340 Republic of Korea
8. Physical Science and Engineering Division (PSE) King Abdullah University of Science and Technology (KAUST) Thuwal 23955 Saudi Arabia
9. Department of Physics State Key Laboratory of Surface Physics Fudan University Yangpu Shanghai 200433 China