We report a systematic investigation of orthorhombic perovskite-type RCrO 3 powder samples by Raman scattering for nine different rare earth R 3+ cations (R = Y, La, Pr, Sm, Gd, Dy, Ho, Yb, Lu). The roomtemperature Raman spectra and the associated phonon mode assignment provide reference data for structural investigation of the whole series of RCrO 3 orthochromites and phonon ab-initio calculations.The assignment of the chromite spectra and comparison with Raman data on other orthorhombic perovskites allows correlating the phonon modes with the structural distortions in the RCrO 3 series. In particular, two A g modes are identified as octahedra rotation soft modes as their positions scale linearly with the octahedra tilt angle of the CrO 6 octahedra.

We report a Raman scattering study of six rare earth orthoferrites RFeO3, with R = La, Sm, Eu, Gd, Tb, Dy. The use of extensive polarized Raman scattering of SmFeO3 and first-principles calculations enable the assignment of the observed phonon modes to vibrational symmetries and atomic displacements. The assignment of the spectra and their comparison throughout the whole series allows correlating the phonon modes with the orthorhombic structural distortions of RFeO3 perovskites. In particular, the positions of two specific Ag modes scale linearly with the two FeO6 octahedra tilt angles, allowing the distortion throughout the series. At variance with literature, we find that the two octahedra tilt angles scale differently with the vibration frequencies of their respective Ag modes. This behavior as well as the general relations between the tilt angles, the frequencies of the associated modes and the ionic radii are rationalized in a simple Landau model. The reported Raman spectra and associated phonon-mode assignment provide reference data for structural investigations of the whole series of orthoferrites.

We report an investigation of perovskite-type LaNiO3 thin films by Raman scattering in both various scattering configurations and as a function of temperature. The room-temperature Raman spectra and the associated phonon mode assignment provide reference data for phonon calculations and for the use of Raman scattering for structural investigations of LaNiO3, namely the effect of strain in thin films or heterostructures. The temperature-dependent Raman spectra from 80 to 900 K are characterized by the softening of the rotational A1g mode, which suggest a decreasing rhombohedral distortion towards the ideal cubic structure with increasing temperature