Raman scattering and phase transitions in fluorides with elpasolite structure

Raman scattering spectra of Rb₂KHoF₆ and Rb₂KDyF₆ crystals have been studied in temperature range from 20 K to 399 K and from 7 K to 500 K respectively. Raman spectra of Rb₂KHoF₆ crystal are distorted due to the fluorescence process. Parameters of Raman lines have been quantitatively analyzed. The investigation points to the considerable role of CX₆ groups in the temperature phase transition in Rb₂KHoF₆ and Rb₂KDyF₆ crystals. The anomalies of spectra changes with temperature testify the first order phase transitions in these crystals.