Infrared phonon spectrum of pure and doped LaMnO3

The infrared reflectance spectra of two LaMnO3 crystals (pure and doped) have been measured at various temperatures between 300 and 10 K. The infrared active phonons of the two samples have been studied in detail and have been compared to recent lattice dynamics calculations. In the case of the undoped LaMnO3, the number of infrared active phonons agrees with the predictions of group theory. In contrast the phonon structures of the doped sample are broader and do not allow to identify all the expected lines.