1. Institute for Single Crystals, National Academy of Sciences of Ukraine, 60 Nauky Ave., Kharkiv 61072, Ukraine
2. V.N. Karazin Kharkiv National University, 4 Svobody Square, Kharkiv 61022, Ukraine
3. B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine, 47 Nauky Ave., Kharkiv 61103, Ukraine