1. B. Verkin Institute for Low Temperature Physics and Engineering
of the National Academy of Sciences of Ukraine, Kharkiv 61103, Ukraine
2. V. N. Karazin Kharkiv National University, Kharkiv 61022,
Ukraine
3. Institute for Condensed Matter Physics, TU-Braunschweig,
Braunschweig 38106, Germany
4. Laboratory for Emerging Nanometrology and International
Graduate School of Metrology, TU-Braunschweig, Braunschweig 38106, Germany
5. L. V. Kirenskii Institute of Physics, Siberian Branch of the
Russian Academy of Sciences, Krasnoyarsk 660036, Russia