Very large dielectric response of thin ferroelectric films with the dead layers

We study the dielectric response of ferroelectric (FE) thin films with "dead" dielectric layer at the interface with electrodes. The domain structure inevitably forms in the FE film in presence of the dead layer. As a result, the effective dielectric constant of the capacitor $\epsilon_{eff}$ increases abruptly when the dead layer is thin and, consequently, the pattern of 180-degree domains becomes "soft". We compare the exact results for this problem with the description in terms of a popular "capacitor" model, which is shown to give qualitatively incorrect results. We relate the present results to fatigue observed in thin ferroelectric films.Comment: 5 pages, REVTeX 3.1 with one eps-figure. A note added that the linear response is not changed by electromechanical effect. To appear in Phys. Rev.