Far infrared properties of the incommensurate ferroelectric Rb2ZnCl 4

Abstract

Dielectric spectra of Rb2ZnCl4 were determined in the 6-400 cm-1 region for 300 and 90 K. In the 30-400 cm -1 region they were evaluated from bulk reflectivity measurements, in the 6-22 cm-1 region they were calculated from complex transmittance measurements performed on a tunable monochromatic BWO spectrometer. All polar modes were approximately assigned and their parameters determined. No amplitudon and phason were observed in the incommensurate phase because of a high background absorption. A hard A1 mode at 18 cm-1 was seen below 130 K in agreement with Raman results