[1] Xianyang Normal Univ, Coll Phys Elect Engn, Xianyang 712000, Peoples R China
[2] Northwestern Polytech Univ, MOE Key Lab Mat Phys & Chem Extraordinary Condit, Xian 710072, Peoples R China
[3] Northwestern Polytech Univ, Shaanxi Key Lab Condensed Matter Struct & Propert, Sch Phys Sci & Technol, Xian 710072, Peoples R China
[4] Northwestern Polytech Univ, Inst Res & Dev, Shenzhen 518057, Peoples R China
[5] Xian Univ Technol, Sch Mat Sci & Engn, Xian 710048, Peoples R China
[6] Guangdong Acad Sci, Inst New Mat, Guangzhou 510650, Peoples R China
[7] Baotou Res Inst Rare Earth, Baotou 014030, Peoples R China
[8] State Key Lab Baiyunobo Rare Earth Resource Res &, Baotou 014030, Peoples R China