The Contribution of Domain‐Wall Oscillations to the Small‐Signal Permittivity of Triglycine Sulphate

The complex permittivity ϵ * of ferroelectric triglycine sulphate is measured in a weak ac field in the frequency range 5 × 10 2 to 5 × 10 7 Hz as a function of the net polarization P a of the sample. The value of P a is adjusted in steps by charge supplied from a parallel capacitor. Throughout the frequency range both components of ϵ * are larger for crystals with | P a |≠| P s | than for a single‐domain crystal with | P a | = | P s |. This indicates a contribution Δϵ w * to the permittivity by the domain walls. The imaginary component Δϵ w ″ is an order of magnitude greater than the value of ϵ″ of a singel‐domain crystal; Δϵ w ′ is up to five times larger than the ϵ′ of a single‐domain crystal. The frequency dependence of Δ w * suggests contributions from two different mechanisms. The frequency dependence of one of them is given approximately by the Debye equations with τ ≈ 10 −7 s. Both components of the second contribution to Δϵ w * decrease monotonically with frequency. The probable mechanisms of these contributions are discussed.