International audienceFerroelectric and multiferroic materials present a nonlinear variation in their permittivity due to domain wall motion. Currently, this variation is described either by the Rayleigh law for fields above a threshold or by a power law for soft ferroelectrics. We propose a hyperbolic law based on the contributions of domain walls and intrinsic lattice which includes the two classic approaches. The threshold field is clearly defined by considering reversible and irreversible components of the permittivity. A good agreement between the hyperbolic law and experimental data is obtained. Moreover, we show that the threshold field obeys to the Volgel-Fulcher law

International audienceFerroelectric materials subjected to a DC electric field have their dielectric permittivity which decreases with time. This is connected to the reorganization of the domain walls to achieve a more stable configuration. We propose here to study the domain walls motion when the material is subjected to an electrical field. We use the hyperbolic law (generalized Rayleigh law) for contributions related to the walls. This allows to clearly identifying the domain walls as responsible for the time decay of the permittivity

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