Effect of thickness and frequency of applied field on the switching dynamics of multiferroic bismuth ferrite thin films

Epitaxial films of multiferroic BiFeO3 (BFO) with different thicknesses are grown on SrRuO3 buffered SrTiO3 (001) substrates using the pulsed laser deposition technique. The room-temperature polarization-voltage (P-V) hysteresis loop, leakage current and average domain size of films with varying thicknesses have been investigated. The frequency dependence of the coercive voltage and variation of the coercive voltage as a function of film thickness are ascertained to examine the validity of the Ishibashi-Orihara model and the semi-empirical Kay-Dunn scaling relationship, respectively. The results demonstrate that at room temperature the BFO films indeed follow the Ishibashi-Orihara (I-O) model and Kay-Dunn scaling law. The dimensionality of the domains acquired by piezoresponse force microscopy imaging further validates that found from the I-O model scaling exponent and is consistent with Kittel's law regarding dependence of domain width on film thickness. These combined results elucidate the fundamental properties that govern the switching kinetics of BFO and are relevant for BFO-based multiferroic materials in next generation logic and memory devices operating over a wide range of frequencies.