Composition‐Dependent Ferroelectricity of LuFeO₃ Orthoferrite Thin Films

Abstract This work characterizes the structural, magnetic, and ferroelectric properties of epitaxial LuFeO₃ orthoferrite thin films with different Lu/Fe ratios. LuFeO₃ thin films are grown by pulsed laser deposition on SrTiO₃ substrates with Lu/Fe ratio ranging from 0.6 to 1.5. LuFeO₃ is antiferromagnetic with a weak canted moment perpendicular to the film plane. Piezoresponse force microscopy imaging and switching spectroscopy reveal room temperature ferroelectricity in Lu‐rich and Fe‐rich films, whereas the stoichiometric film shows little polarization. Ferroelectricity in Lu‐rich films is present for a range of deposition conditions and crystallographic orientations. Positive‐up‐negative‐down ferroelectric measurements on a Lu‐rich film yield ≈13 µC cm⁻² of switchable polarization, although the film also shows electrical leakage. The ferroelectric response is attributed to antisite defects analogous to that of Y‐rich YFeO₃, yielding multiferroicity via defect engineering in a rare earth orthoferrite.