The proton ordering model for the KH$_{ 2}$PO$_{ 4}$ type ferroelectrics is modified by taking into account the dependence of the effective dipole moments on the proton ordering parameter. Within the four-particle cluster approximation we calculate the crystal polarization and explore the electrocaloric effect. Smearing of the ferroelectric phase transition by a longitudinal electric field is described. A good agreement with experiment is obtained.
Categories: cond-mat.mtrl-sci