Epitaxial Iron Oxides via Scalable Solution-Based Growth: Structure and Defect-Mediated Properties

We demonstrate substrate-selective epitaxial growth of iron-oxide polymorphs by spray pyrolysis, establishing a scalable, nonvacuum route to crystalline magnetic oxides. Under identical deposition conditions (718 ± 5 K), corundum α-Fe2O3 is stabilized on c-Al2O3(0001), whereas spinel γ-Fe2O3 forms on MgO(100), highlighting the dominant role of interfacial lattice matching in phase selection via coherent interface stabilization of the lowest-energy polymorph. X-ray diffraction, ϕ-scans, RSM and ex situ RHEED confirm high-quality epitaxy, with instrument-corrected rocking-curve FWHM of 0.126° for α-Fe2O3 and 0.160° for γ-Fe2O3. Magnetic measurements reveal an in-plane easy axis for both films, with bulk-like ferrimagnetic order in γ-Fe2O3 (∼440 emu·cm–3) and an enhanced canted state in α-Fe2O3 (∼120 emu·cm–3). Temperature-dependent transport further links functional response to the defect landscape, with antiphase-boundary-mediated magnetoresistance in γ-Fe2O3 and a suppressed Morin transition in α-Fe2O3. These results demonstrate that spray pyrolysis enables phase-engineered epitaxial iron oxides with structural and magnetic quality comparable to vacuum-based methods.