Defect‐Enhanced Polarization Switching in the Improper Ferroelectric LuFeO3

Results of switching behavior of the improper ferroelectric LuFeO3 are presented. Using a model set of films prepared under controlled chemical and growth‐rate conditions, it is shown that defects can reduce the quasi‐static switching voltage by up to 40% in qualitative agreement with first‐principles calculations. Switching studies show that the coercive field has a stronger frequency dispersion for the improper ferroelectrics compared to a proper ferroelectric such as PbTiO3. It is concluded that the primary structural order parameter controls the switching dynamics of such improper ferroelectrics. Polarization switching in epitaxial thin films of the improper ferroelectric LuFeO3 shows that the inclusion of point defects can reduce the coercive electric field. Frequency dispersion of the switching field is larger when the thickness is reduced, suggesting that the mechanical constraint induced by the substrates may play a key role in the switching of the polarization state.