Frequency dependence of dielectric saturation.
Dielectric saturation originates from the upper bound to dipole orientation, reached when all dipoles are aligned "perfectly" with respect to the electric field. For Debye-type dynamics, it is well established that the saturation effect is diminished at high frequencies relative to its steady-state value. Here, it is argued that a similar frequency dependence of this nonlinear dielectric effect is expected also for dispersive dynamics, provided that the system is dynamically homogeneous. By contrast, more realistic relaxation time dispersions based upon heterogeneous dynamics display a strongly reduced frequency dependence of dielectric saturation. Calculations demonstrate this effect in terms of both the fundamental and the third harmonic frequency susceptibilities. The relations of signatures of nonlinearity in different Fourier components of the response are briefly discussed.
I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany.
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