Effect of Gd3+ impurity on the Raman spectra in layered Cs-Dy double molybdate

Raman spectra of CsDy(MoO4)2 and CsDy0.93Gd0.07(MoO4)2 crystals were investigated in 300-4.2K range using double monochromator and argon laser as radiation source. Accurate polarization measurements of Raman spectra in CsDy(MoO4)2 and CsDy0.93Gd0.07(MoO4)2 showed that spectra of two compounds were identical when cooling down to 50K. It means that vibrational spectrum of the crystal with Gd3+ impurity manifests the single-mode behaviour. The presence of Gd3+ impurity affects the temperature and the character of phase transformation, taking place near 42K, where volume jump is observed. This influences the frequency position of Raman spectral lines. Phase transformation affects mainly the low-frequency spectrum, related with external vibrations of tetrahedral anions