1. School of Physics and State Key Laboratory of Crystal Materials Shandong University Jinan 250100 P. R. China
2. School of Information and Automation Engineering Qilu University of Technology (Shandong Academy of Science) Jinan 250353 P. R. China
3. Spintronics Institute University of Jinan Jinan 250022 P. R. China
4. School of Instrumentation Science and Engineering Condensed Matter Science and Technology Institute Harbin Institute of Technology Harbin 150080 P. R. China
5. Department of Physics University of Bath Bath BA2 7AY UK
6. Center for High Pressure Science and Technology Advanced Research Shanghai 201203 P. R. China