1. O.O. Galkin Donetsk Institute for Physics and Engineering, N.A.S., Pr. Nauki, 46, 03028 Kyiv, Ukraine
2. Vasyl' Stus Donetsk National University, Ul. 600-letiia 21, 21021 Vinnitsa, Ukraine
3. Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02668 Warsaw, Poland
4. G.V. Kurdyumov Institute for Metal Physics of the N.A.S., Ac. Vernadsky Bld 36, 03142 Kyiv, Ukraine