1. Department of Physics, Condensed Matter Science and Technology Institute; Harbin Institute of Technology; Harbin 150001 China
2. Department of Material Physics; School of Applied Sciences; Harbin University of Science and Technology; Harbin 150080 China
3. Department of Materials Science and Engineering; National Laboratory of Solid State Microstructures, Nanjing University; Nanjing 210093 China
4. Institute for Advanced Ceramics; School of Materials Science and Engineering; Harbin Institute of Technology; Harbin 150001 China
5. Materials Research Institute; The Pennsylvania State University; University Park Pennsylvania 16802