Comparative Raman study of isostructural YCrO3 and YMnO3: Effects of structural distortions and twinning

Polarized Raman spectra of isostructural orthorhombic YCrO3 and YMnO3 single crystals were collected at the same conditions using different laser excitation in the visible range. The symmetry of the observed lines was determined and they were assigned to definite atomic vibrations based on lattice dynamical calculations. The frequencies of the lines of the same origin in both compounds are close, however, their intensities differ significantly. While the different intensity of the modes, activated by the Jahn-Teller distortion, can be explained by the different magnitude of this distortion in the two compounds, the cause of the reduced intensity of other lines in the low-frequency region in the Raman spectra of YMnO3 is likely due to the fine twinning of the crystal.