Dielectric Dispersion in Ferroelectric Ca₂Sr(C₂H₅CO₂)₆

Abstract

The complex dielectric constant ε(ω) of Ca₂Sr(C₂H₅CO₂)₆ along the tetragonal c-axis was measured at 54 different frequencies between 10³ Hz and 10⁹ Hz. In the paraelectric phase, ε(ω) is well described by the Debye dispersion formula with a single relaxation time except in the vicinity of the Curie temperature T_c. In the temperature region of 0<T−T_c\lesssim3 K, the second dispersion of a resonant type is observed in addition to the Debye type dispersion. The temperature dependence of the relaxation time τ of the Debye dispersion is well expressed in the temperature range 1 K\lesssimT−T_c by a power law, τ∝(T−T_c)^−Δ with Δ=1.31, which is larger than the critical exponent γ=1.28 for the static dielectric constant obtained by extrapolation of the Debye dispersion.