Complementarity of phase transition and stochastic resonance in spatially restricted systems.

We study the linear response in a soft potential, the Landau-type temperature dependence of which is responsible for the monostable-to-bistable transformation. The system can be considered as a model of a sample with internal noise, where a second-order phase transition takes place in the bulk limit. The intensity of noise influencing the order parameter is supposed to be a function of the volume. We demonstrate that the anomaly of susceptibility at the phase transition point described by the Landau phase transition theory transforms into the maximal response caused by stochastic resonance if the volume of the system decreases. The phenomenon can be treated also as an increase in the diffuseness of a phase transition with lowering of the critical temperature. We suggest that it is this crossover that contributes to the mechanism of dielectric peculiarities in ceramic and relaxor ferroelectrics.