Construction of the misfit strain–temperature phase diagrams of epitaxial BiFeO3 thin film

A nonlinear phenomenological theory was described for the epitaxial BiFeO3 (BFO) thin films with single domain structure. With the consideration of the mechanical substrate effect, the “misfit strain–temperature” phase diagram is constructed for the BFO thin film by numerical calculations. It is found that the polarization instabilities result in the formation of new domain states forbidden in bulk crystals, which has been observed in the experiments.