Dielectric permittivity dynamics of Ba1-xSrxTiO3 epitaxial films (x=0.75):Microstructure and depolarization effects

Trilayer epitaxial heterostructures including metal oxide electrodes (SrRuO 3, 200 nm) and a sandwiched dielectric layer (Ba0.25Sr0.75TiO3, 700 nm) wer e grown by laser ablation on (001)LaAlO3 substrates. The maximum permittivi ty of the Ba0.25Sr0.75TiO3 layer (epsilon'/epsilon (0) approximate to 3700) was obtained at T-M = 160 K and an external electric field E approximate t o 10(6) V/m. The epsilon'(T) dependence for the Ba0.25Sr0.75TiO3 layer in t he paraelectric phase is well fitted by the Curie-Weiss relation, with the Curie constant and the Weiss temperature differing only insignificantly fro m the corresponding bulk values. The change in the permittivity of the Ba0. 25Sr0.75TiO3 layer induced by the application of a +/-2.5 V bias voltage to the electrodes reached as high as 85%. The electric-field dependence of th e polarization retained clearly pronounced saturated hysteresis loops up to temperatures 10-15 K above T-M. (C) 2001 MAIK "Nauka/Interperiodica".