1. MOE Key Laboratory of Materials Physics and Chemistry under Extraordinary Conditions, School of Natural and Applied Sciences, Northwestern Polytechnical University, Xi'an 710072, China
2. Ames Laboratory-USDOE, Iowa State University, Ames, Iowa 50011, USA
3. School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China
4. Department of Applied Physics, College of Science, Zhejiang University of Technology, Hangzhou 310023, China
5. Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA