Effect of ac field on the dielectric behavior in epitaxial films of relaxor ferroelectricPbMg1∕3Nb2∕3O3

Abstract

The dynamic dielectric response of epitaxial $\mathrm{Pb}{\mathrm{Mg}}_{1∕3}{\mathrm{Nb}}_{2∕3}{\mathrm{O}}_{3}$ thin films was experimentally studied as a function of amplitude of ac electric field including very large amplitudes (to $10\phantom{\rule{0.3em}{0ex}}\mathrm{MV}∕\mathrm{m}$). For all amplitudes, a typical glasslike relaxor behavior was evidenced by the Vogel-Fulcher relationship, empirical scaling of the dielectric peak, and a broadening of the relaxation time spectra on cooling. With increasing amplitude of the ac field, both the temperature of the dielectric maxima and the freezing temperature decreased, the relaxation time spectrum became narrower, and the nonlinear permittivity was nonmonotonic. The comparison of the observed dielectric behavior with that under an applied small dc electric field and with the results of modeling revealed an orientational contribution to polarization.