Dynamic dielectric nonlinearity in epitaxial thin-film relaxors and ferroelectrics

The dynamic dielectric response of epitaxial thin-film PbMg1/3Nb2/3O3, PbSc0.5Nb0.5O3, and Ba0.4Sr0.6TiO3 was experimentally studied as a function of temperature, frequency, and amplitude of ac electric field (to 10 MV/m). In thin-film relaxors at all amplitudes, a glasslike behavior was evidenced by Vogel-Fulcher relationship, scaling of the dielectric peak, and broadening of the relaxation time spectra on cooling. Both this and the nonlinear dielectric response were consistent with reorientation of randomly interacting dipoles at presence of random fields. In thin-film ferroelectrics, a relaxorlike nonlinear dielectric behavior was found. As a reason for this, possible coexistence of polar and nonpolar regions was discussed.