1. Taras Shevchenko National University of Kyiv; 64 Volodymyrska Str.; 01601 Kyiv Ukraine
2. B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine; 47 Lenin Ave.; 61103 Kharkov Ukraine
3. Universite d'Aix-Marseille; IM2NP, 13397 Marseille Cedex 20; France
4. Technical University of Ilmenau; Weimarer Str. 25, 98683 Ilmenau; Germany