Mössbauer Study of the Ferroelectric Phase Transition in Potassium Ferrocyanide Trihydrate

An increase in the area of the Mössbauer spectrum at the ferroelectric transition point has been observed in single crystals of potassium ferrocyanide trihydrate (KFCT), for spectra with the $\gamma$ beam in a direction near the ferroelectric [$10\overline{1}$] axis. Also an anomalous change in the center shift appears at the transition point. This behavior is related to polarization effects, due to the presence of small quadrupole splitting in KFCT and to changes in the orientation of the electric field gradient caused by the onset of ferroelectricity.