Field dependent specific heat of PbTiO₃ and KNbO₃ ferroelectric perovskites

59-63An expression has been obtained for the specific heat of anharmonic pure PbTiO3 and KNbO3 ferroelectric perovskites using double-time Green’s function along with Silverman-Joseph modified Hamiltonian which includes anharmonicity up to the fourth order due to the interaction of the soft mode. The electric field and temperature dependence of the soft mode and the specific heat has been studied for both the crystals. The specific heat decreases with increasing external electric field and increases with increasing temperature. In the low field’s region, the effect of temperature ceases and the change in specific heat arises mainly due to higher order anharmonic terms. Anharmonicity is necessary in these crystals to observe these effects