1. Key Laboratory of Special Function Materials and Structure Design; Ministry of Education; Lanzhou University; Lanzhou 730000 China
2. Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education; Lanzhou University; Lanzhou 730000 China
3. Department of Electronic Material, School of Physical Science and Technology; Lanzhou University; Lanzhou 730000 China
4. Laboratory of Beijing Synchrotron Radiation; Institute of High Energy Physics; Chinese Academy of Sciences; Beijing 100049 China