1. Institute of Microelectronics, Chinese Academy of Sciences 1 , 100029, Beijing, China
2. University of Chinese Academy of Sciences 2 , 100049, Beijing, China
3. School of Microelectronics, South China University of Technology 3 , 510641 Guangzhou, China
4. Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University 4 , Lanzhou 730000, China