Mössbauer-Effect Study of Ferroelectric Potassium Ferrocyanide Trihydrate

The recoilless fraction and thermal shift in the M\"ossbauer spectra of potassium ferrocyanide trihydrate (KFCT) have been studied around the ferroelectric transition temperature. In contrast to the results of Hazony et al., but in agreement with Gleason and Walker, no anomaly was found. Estimates are presented which show that a 2% or smaller change in the recoilless fraction f may reasonably be expected for a soft-phonon-mode model of KFCT. Since the experiments place an upper limit of about 3% on the change in f, the possibility of a soft-phonon mode cannot be ruled out.