1. V. Stefanyk Precarphatian National University, Shevchenko Str., 57, 76025 Ivano‐Frankivsk, Ukraine
2. G.V. Kurdyumov Institute for Metal Physics of NASU, Vernadsky Blvd. 36, 03680 Kyiv, Ukraine
3. Yu. Fed'kovych Chernivtsi National University, Kotsyubynsky Str., 2, 58032 Chernivtsi, Ukraine