Relaxational dynamics of polar nanodomains in Sr1-xCaxTiO3, x=0.002

The dielectric permittivity of Sr1-xCaxTiO3, x = 0.002, measured at frequencies 10(-3) less than or equal to f less than or equal to 10(7) Hz and temperatures 1.5 less than or equal to T less than or equal to 15 K, exhibits enhanced loss. epsilon ''(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 approximate to 3 K athermal quantum tunneling starts to dominate both epsilon ''(f) and P(t).