1. Berdyansk State Pedagogical University,The Department of Physics and Methods of Teaching Physics,Berdyansk,Ukraine
2. L.N. Gumilyov Eurasian National University,Nur-Sultan,Kazakhstan,010008
3. Berdyansk State Pedagogical University,Berdyansk,Ukraine
4. Institute of Solid State Physics, University of Latvia,Riga,Latvia,LV-1063