1. School of Physical Science and Technology & Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education Lanzhou University Lanzhou 730000 China
2. School of Physical Science and Technology & Lanzhou Center for Theoretical Physics & Key Laboratory of Theoretical Physics of Gansu Province Lanzhou University Lanzhou 730000 China
3. Department of Microelectronic Science and Engineering School of Physical Science and Technology Ningbo University Ningbo 315211 China