Low-frequency dielectric dispersion in tri-glycine sulphate

Measurements are reported of the complex dielectric permittivity, ε(ω), of single crystal tri-glycine sulphate (TGS) at temperatures on either side of the ferroelectric Curie temperature, Tc, covering the frequency range ω/2π = 10-105 Hz. By contrast with the reported strong dispersion in the GHz region, the dielectric loss and the real part of the susceptibility, x(ω) - ε(ω) — ε∞, follow the empirical relation χ'(ω) ∞χ'(ω) ∞ ωx-1 which gives a frequency-independent ratio χ'(ω)/χ'(ω) = cot(ηπ/2) in conformity with the response of most other solid dielectrics. The physical significance of this result in relation to the interpretation of the polarization mechanisms in ferroelectrics is discussed.