Paraelectric in a strong high-frequency field

A change in the effective permittivity of a ferroelectric film in the paraelectric phase under the action of a strong high-frequency field (nonequilibrium soft mode heating) is considered. It is shown that this effect must be most clearly pronounced far from the resonance (ω0[graphic not available: see fulltext] ωsm), rather than for the external field frequency ω0 close to the soft mode frequency ωsm. The effective permittivity as a function of the high-frequency field amplitude is determined using a phenomenological approach and within the framework of a microscopic theory based on a simple model of a displacement-type ferroelectric.