1. B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine, 47 Nauky Ave., Kharkov 61103, Ukraine
2. National Technical University “Kharkov Polytechnic Institute,” 2, Kyrpychova str., Kharkov 61002, Ukraine
3. Institute for Low Temperatures and Structure Research Polish Academy of Sciences, ul. Okólna 2, Wrocław 50-422, Poland