[1] Russian Acad Sci, Shubnikov Inst Crystallog, Moscow 119333, Russia
[2] Dagestan State Univ, Makhachkala 367000, Russia
[3] Natl Acad Sci Ukraine, Inst Single Crystals, UA-61103 Kharkov, Ukraine
[4] Natl Res Ctr, Kurchatov Inst, Moscow 123182, Russia