Relaxational dynamics of polar nanodomains in Sr _{1 − x} Ca _x TiO ₃ x = 0.002

Abstract

The dielectric permittivity of Sr1 − xCaxTiO3, x = 0.002, measured at frequencies 10−3 ⩽ f ⩽ 107 Hz and temperatures 1.5 ⩽ T ⩽ 15 K, exhibits enhanced loss, ε''(f), on its low-f slope. This contrasts with conventional glassy dynamics and is attributed to dynamic heterogeneity involving thermally activated relaxation of dynamically coupled mesoscopic domains. Crossover into non-activated dynamics occurs at very low f as corroborated by temporal relaxation studies of the field-induced polarization P. Below T ≈ 3 K athermal quantum tunneling starts to dominate both ε''(f) and P(t).