Simplest models to explain dielectric nonlinearity

It is shown that qualitatively-correct explanation of dielectric permittivity nonlinearity (the dependence of permittivity on the electric field) can be obtained from a consideration of even the simplest model representations of electronic, ionic and dipole polarization as for the elastic (strain) so for the thermal (relaxation) mechanism of the polarized state. Paraelectric nonlinearity is evaluated using Landau thermodynamics theory.