The phase transitions in ferroelectric films described by a transverse spin-1/2 Ising model

The critical temperature in ferroelectric films described by a transverse s pin-1/2 Ising model is studied using effective;field theory along with a pr obability distribution technique. We discuss an L layer film of simple cubi c symmetry with nearest-neighbor interactions in which the strengths of the interactions are different from the bulk values in the surface layers. We derive the phase diagram, the magnetization profiles and the susceptibiliti es. In such films, the critical temperature can shift to either a lower or higher temperature compared with the corresponding bulk value. The film lon gitudinal susceptibility diverges at the film critical temperature.