1. State Key Laboratory of Powder Metallurgy and Powder Metallurgy Research Institute, Central South University, Changsha 410083, People's Republic of China
2. School of Physics and Electronics, Central South University, Changsha 410083, People's Republic of China
3. School of Physics and Technology, Xinjiang University, Urumqi 830046, People's Republic of China
4. Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada