Abstract
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.
Original language | English |
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Pages (from-to) | 4205-4211 |
Number of pages | 7 |
Journal | Crystal Growth and Design |
Volume | 19 |
Issue number | 8 |
DOIs | |
State | Published - 7 Aug 2019 |