Non-Debye domain-wall-induced dielectric response inSr0.61−xCexBa0.39Nb2O6

Abstract

Two different non-Debye dielectric spectra are observed in a polydomain relaxor-ferroelectric ${\mathrm{Sr}}_{0.61\ensuremath{-}x}{\mathrm{Ba}}_{0.39}{\mathrm{Nb}}_{2}{\mathrm{O}}_{6}:{\mathrm{Ce}}_{x}^{3+}$ single crystal in the vicinity of its transition temperature, ${T}_{c}\ensuremath{\approx}320 \mathrm{K}.$ At infralow frequencies the susceptibility varies as ${\ensuremath{\chi}}^{*}\ensuremath{\propto}{\ensuremath{\omega}}^{\ensuremath{-}\ensuremath{\beta}},$ $\ensuremath{\beta}\ensuremath{\approx}0.2,$ and is attributed to an irreversible creep-like viscous motion of domain walls, while logarithmic dispersion due to reversible wall relaxation [T. Nattermann, Y. Shapir, and I. Vilfan, Phys. Rev. B $42,$ 8577 (1990)] occurs at larger $\ensuremath{\omega}.$