1. V. N. Karazin Kharkiv National University, Kharkiv 61022, Ukraine
2. IFIMUP, Departamento de Fisica, Universidade de Porto, Porto 4169-007, Portugal
3. Ukrainian State Academy of Railway Transport, Kharkiv 61050, Ukraine
4. B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine, Kharkiv 61103, Ukraine