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.