Cluster and domain-wall dynamics of ferroelectric Sr1−xCaxTiO3

Abstract

The dielectric permittivity of the xy-type random-field system ${\mathrm{Sr}}_{0.942}$ ${\mathrm{Ca}}_{0.058}$ ${\mathrm{TiO}}_3$ is measured at frequencies 30<f${<10\mathrm{}}^7$ Hz and temperatures 7.5<T<200 K. At all temperatures a Debye-type, monodispersive process dominates with relaxation times τ∼${10}^{\mathrm{-}5}$ s. It is attributed to off-center ${\mathrm{Ca}}^{2+}$ dipole dynamics, which also determines the low-T ferroelectric bulk relaxation. At T<$T_c$∼35 K an additional polydispersive Cole-Cole–type domain wall relaxation is observed. Its large spectrum of relaxation times centered around τ∼${10}^{\mathrm{-}3}$ s gives rise to glasslike behavior at low T. Experiments with external electric fields competing with the built-in random fields are discussed.