Surface Modification of the Spontaneous Polarization in Ferroelectric Thin Films

The surface effects on the spontaneous polarization in ferroelectric thin films were discussed based on the Ising model in a transverse field. Both the modifications of the transverse field and the strength of coupling in the surface layer were taken into consideration. At the temperature much lower than the Curie point, the behaviour of the spontaneous polarization deviates from the phenomenological description. The surface effects might lead to the spontaneous polarization and the Curie temperature changing in different direction. The theory gives a reasonable description of the experimental temperature dependence of the spontaneous polarization of triglycine sulfate thin films in the literature.