1. Institute of Monocrystals of NASUkraine, pr. Nauki, 60, Khar'kov, 61072, Ukraine
2. V. N. Karazin Kharkov National University, pl. Svobody, 4, Khar'kov, 61022, Ukraine
3. B.I.Verkin Institute for Low Temperature Physics and Engineering of NAS Ukraine pr. Nauki, 47, Khar'kov, 61103, Ukraine