Here we demonstrate a new monoclinic iron oxide phase (μ-Fe2O3), epitaxially stabilized by growth on (010) β-Ga2O3. Density functional theory (DFT) calculations find that the lattice parameters of freestanding μ-Fe2O3 are within ∼1% of those of β-Ga2O3, and that its energy of formation is comparable to that of naturally abundant Fe2O3 polytypes. A superlattice of μ-Fe2O3/β-Ga2O3 is grown by plasma assisted molecular beam epitaxy, with resulting high-resolution X-ray diffraction (XRD) measurements indicating that the μ-Fe2O3 layers are lattice-matched to the substrate. The measured out-of-plane (b) lattice parameter of 3.12 ± 0.4 Å is in agreement with the predicted lattice constants and atomic-resolution scanning transmission electron microscopy (STEM) images confirm complete registry of the μ-Fe2O3 layers with β-Ga2O3. Finally, DFT modeling predicts that bulk μ-Fe2O3 is antiferromagnetic, while the interface region between μ-Fe2O3 and β-Ga2O3 leads to ferromagnetic coupling between interface Fe3+ cations selectively occupying tetrahedral positions. Magnetic hysteresis persisting to room temperature is observed via SQUID measurements, consistent with the computationally predicted interface magnetism.
|Number of pages||7|
|Journal||Crystal Growth and Design|
|State||Published - 7 Aug 2019|