[1] Chongqing Univ Posts and Telecommun, Coll Sci, Chongqing 400065, Peoples R China
[2] Polish Acad Sci, Inst Phys, Al Lotnikow 32-46, PL-02668 Warsaw, Poland
[3] Chongqing Univ Posts & Telecommun, Coll Optoelect Engn, Chongqing 400065, Peoples R China
[4] Gen Res Inst Nonferrous Met, Natl Engn Res Ctr Rare Earth Mat, Beijing 100088, Peoples R China
[5] Grirem Adv Mat Co Ltd, Beijing 100088, Peoples R China