Optical phonons and its effect on physical properties of rare-earth orthoferrites RFeO3 (R = La, Nd, Gd, Dy, Er): IR reflectivity measurements

We have investigated the infrared reflectivity, UV-visible spectra and electrical property of polycrystalline RFeO3 (R = La, Nd, Gd, Dy, Er) synthesized by sol-gel method. Analysis of IR reflectivity spectra through Lorentz oscillator model has led to the observation of 14 IR active phonon modes out of 25 predicted modes. The results have been discussed in terms of different phonon bands related to the origin of atomic vibrations, which provides information about the structural evolution. The energy bandgap similar or equal to 1.67-1.90 eV estimated from optical conductivity (sigma(omega)) spectrum is found consistent both with that calculated from UV-visible spectra and estimated from electrical measurements.