1. School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, P. R. China
2. Key Laboratory of Low Dimensional Materials and Application Technology of Ministry of Education, Xiangtan University, Xiangtan 411105, P. R. China
3. Institute for Superconducting and Electronic Materials, Australian Institute of Innovative Materials, Innovation Campus, University of Wollongong, Wollongong, NSW 2500, Australia