1. School of Physical Science and Technology, Inner Mongolia University, Hohhot 010021, China
2. School of Materials Science and Engineering, Inner Mongolia University of Technology, Hohhot 010051, China
3. School of Baotou Research Institute of Rare Earths, Baotou 014060, China
4. School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
5. University of Michigan-Shanghai Jiao Tong University Joint Institute, Shanghai Jiao Tong University, Shanghai 200240, China