1. Guangdong Province Key Laboratory of Rare Earth Development and Application, Institute of Rare Metals, Guangdong Academy of Sciences, Guangzhou 510651, P. R. China
2. College of Sciences & CQUPT-BUL Innovation Institute, Chongqing University of Posts and Telecommunications, Chongqing, 400065, P. R. China
3. Institute of Physics, University of Tartu, W. Ostwald Str. 1, Tartu 50411, Estonia
4. Faculty of Science and Technology, Jan Dlugosz University, Armii Krajowej 13/15, PL-42200, Częstochowa, Poland
5. RAS, Fed. Res. Ctr KSC SB, Kirensky Inst. Phys., Lab Crystal Phys, Krasnoyarsk 660036, Russia
6. Siberian Fed Univ., Krasnoyarsk 660041, Russia
7. Far Eastern State Transport Univ., Dept. Phys., Khabarovsk 680021, Russia
8. School of Marine Sciences, Sun Yat-Sen University, Zhuhai 510275, P. R. China