An antisite defect mechanism for room temperature ferroelectricity in orthoferrites

Abstract

Single-phase multiferroic materials that allow the coexistence of ferroelectric and magnetic ordering above room temperature are highly desirable, motivating an ongoing search for mechanisms for unconventional ferroelectricity in magnetic oxides. Here, we report an antisite defect mechanism for room temperature ferroelectricity in epitaxial thin films of yttrium orthoferrite, YFeO3, a perovskite-structured canted antiferromagnet. A combination of piezoresponse force microscopy, atomically resolved elemental mapping with aberration corrected scanning transmission electron microscopy and density functional theory calculations reveals that the presence of YFe antisite defects facilitates a non-centrosymmetric distortion promoting ferroelectricity. This mechanism is predicted to work analogously for other rare earth orthoferrites, with a dependence of the polarization on the radius of the rare earth cation. Our work uncovers the distinctive role of antisite defects in providing a mechanism for ferroelectricity in a range of magnetic orthoferrites and further augments the functionality of this family of complex oxides for multiferroic applications.

Antisite Defects Stabilized by Antiphase Boundaries in YFeO3 Thin Films

“…Instead, the outof-plane ferroelectric response remains dominated by the Y Fe antisites. [3] Beyond the polarization, magnetic properties can be impacted by presence of APBs. In the DFT relaxed structure, the oxygen octahedra at the APBs are found to tilt.…”

“…Thin Film Growth: The YFO thin film was grown using pulsed laser deposition on an Nb-doped STO substrate using a KrF excimer laser (λ = 248 nm) with 1.3 J cm −2 fluence and 10 Hz repetition rate. [3] A commercial YFeO 3 target from Plasmaterials Inc. was used for thin film growth. The substrate was held at 900 °C and the oxygen partial pressure was kept at 10 mTorr.…”

“…While the orthoferrite YFeO 3 (YFO) is centrosymmetric (non-polar) and antiferromagnetic, [1,2] it exhibits multiferroic behavior when grown as a thin film under nominally stoichiometric and Y-rich conditions. [3] Specifically, the introduction of Y Fe antisites breaks crystal inversion symmetry (Pbnm to…”

“…While the orthoferrite YFeO 3 (YFO) is centrosymmetric (non‐polar) and antiferromagnetic, [ 1,2 ] it exhibits multiferroic behavior when grown as a thin film under nominally stoichiometric and Y‐rich conditions. [ 3 ] Specifically, the introduction of Y Fe antisites breaks crystal inversion symmetry (Pbnm to R 3 c ) and stabilizes a spontaneous dipole moment that leads to stoichiometry‐dependent ferroelectricity. Although the resulting multiferroic behavior is robust, planar defects are also found in YFO thin films grown on SrTiO 3 , which requires further investigation to gain complete control over the material properties.…”

Double-Bilayer Polar Nanoregions and Mn antisites in (Ca,Sr)3Mn2O7

“…The stabilization mechanism of db-PNRs in CSMO due to Mn antisites is similar to Ti antisites producing PNRs and a switchable polarization in SrTiO 3 40,41 , as well as the recent report of Y antisites leading to room temperature ferroelectricity in yttrium orthoferrite YFeO 3 . 42 Our work…”