Infrared Lattice-Vibration Spectra in NiF2, CoF2, and FeF2

Abstract

The optically active vibration modes of iron group divalent fluorides have been investigated by reflection measurements on single crystals and by optical-transmission studies on sintered powders containing fluorides diluted in polyethylene. The obtained spectra are compared with the theoretical predictions for optical absorption due to photon—phonon interaction. For some spectra Kramers—Krönig inversion was performed, allowing more precise measurements of the optically active normal-modes frequencies and providing an evaluation of the oscillator parameters.