Infrared Phonon Spectra and Lattice Dynamics for NdGaO3

Abstract

Polarized infrared reflected spectra of NdGaO3 crystal are measured at room temperature. The infrared-active phonon frequencies, linewidths and the dielectric constants are obtained by oscillator fitting procedure of the reflective data measured at room temperature. The phonon dispersion curves of NdGaO3 are calculated using a shell model. The B2u mode at 174 cm-1 involves mixedvibrations of the Nd atoms and the GaO6 octahedra, and the higher frequency mode do not involve motion of Nd atoms above 300 cm-1. The linewidth of B2u mode has been analyzed at 174 cm-1, 356 cm-1 and 595 cm-1 using the lattice dynamical perturbative treatment within the cubic anharmonic term in the expansion series ofthe crystal potential energy, and the calculated results reproduces the observedones at room temperature. We found that the linewidth of the B2u mode (174 cm-1) va-ried with increasing temperature by comparison with other phonon peaks (356 cm-1 and 595 cm-1).