1. V.N. Bakul Institute for Superhard Materials, National Academy of Sciences of Ukraine, 2 Avtozavodskaya Street, Kiev 04074, Ukraine
2. Kiev Academic University, 36 Academician Vernadsky Boulevard, Kiev 03142, Ukraine
3. G.V. Kurdyumov Institute for Metal Physics, National Academy of Sciences of Ukraine, 36 Academician Vernadsky Boulevard, Kiev 03142, Ukraine
4. B.I. Verkin Institute for Low Temperature Physics and Engineering, National Academy of Sciences of Ukraine, 47 Nauki Avenue, Kharkov 61103, Ukraine