Surface Effects on Dielectric Susceptibility of a Semi-infiniteFerroelectric

The profile of susceptibility near the surface of a semi-infinite ferroelectric is calculated from Landau free energy. In surface ferroelectric phase, the susceptibility is reduced at surface for |δ| <<β and much enhanced for |δ| ~β Where δ and β are the extrapolation length and the coherent length respectively. In ferroelectric phase, the surface susceptibility is generally reduced for δ<0. But the curve is not monotonic, there is a minimum in the surface layer. For δ >0, the surface susceptibility is reduced for |δ| <<β and enhanced for δ~β. The curve has a maximum in the surface layer.