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Resonance of polarisation mechanisms in alternating fields
μ = qr r κ Frequency, Hz > +
Below its resonance frequency, the ionic mode of polarisation oscillates as seen previously.
μ = qr r +
When the frequency of the applied field is equal to the resonance frequency of the ionic polarisation mechanism, resonance occurs and the amplitude of the oscillations increases. This causes an increase in the polarisation and hence in the dielectric constant.
If the frequency is raised further, to above the resonance frequency of the mechanism, then as we have seen before the ionic mechanism can no longer keep up with the field switching and ceases to contribute to polarisation, leading to a drop in the dielectric constant.
A similar thing happens for the electronic mode of polarisation.
Below resonance frequency