1. Guangdong Provincial Key Laboratory of Optical Information Materials and Technology & Institute for Advanced Materials South China Academy of Advanced Optoelectronics South China Normal University Guangzhou 510006 P. R. China
2. National Center for International Research on Green Optoelectronics South China Normal University Guangzhou 510006 P. R. China
3. Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education Lanzhou University Lanzhou 730000 China
4. College of Science Tianjin University Tianjin 300392 China
5. Laboratory of Solid State Microstructures and Innovation Center of Advanced Microstructures Nanjing University Nanjing 211102 China