[1] Natl Acad Sci Ukraine, B Verkin Inst Low Temp Phys & Engn, 47 Nauky Ave, UA-61103 Kharkov, Ukraine
[2] Polish Acad Sci, Inst Phys, 32-46 Aleja Lotnikow, PL-02668 Warsaw, Poland
[3] Paul Scherrer Inst, Lab Sci Dev & Novel Mat, CH-5232 Villigen, Switzerland