1. College of Sciences, Chongqing University of Posts and Telecommunications, Chongqing 400065, China
2. Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, Warsaw 02-668, Poland
3. Institute of Physics, University of Tartu, W. Ostwald Str. 1, Tartu 50411, Estonia
4. Institute of Physics, Jan Dlugosz University, Armii Krajowej 13/15, Czestochowa PL-42200, Poland
5. Institute of Experimental Physics, University of Gdańsk, Ul. Wita Stwosza 57, 80-952 Gdańsk, Poland
6. Institute for Single Crystals, NAS of Ukraine, Nauky Avenue 60, Kharkov 61001, Ukraine