1. School of Physics and Electronics
2. State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body
3. Hunan University
4. Changsha 410082
5. China
6. College of Mechanical and Vehicle Engineering
7. Institute of Microelectronics of Chinese Academy of Sciences
8. Beijing 100029
9. Key Laboratory of Magnetism and Magnetic Materials of the Ministry of Education
10. School of Physical Science and Technology
11. Lanzhou University
12. Lanzhou 730000