Modified Potassium Dihydrogen Phosphate Model in a Staggered Field

The exact solution of the modified potassium dihydrogen phosphate model of a ferroelectric, previously considered in a direct field only, is now extended to include a staggered field. The thermodynamic properties are found to remain unchanged with the addition of a staggered field; namely, the specific heat vanishes below the transition temperature $T_c$ and diverges as ${(T-T_c)}^{\frac{-1\mathrm{}}{2}}$ above $T_c$. Phase diagrams similar to those of an antiferroelectric in a direct field are obtained. Behavior of the polarizations in both direct and staggered fields is also discussed.