Ferromagnetic Epitaxial μ-Fe$_{2}$O$_{3}$ on β-Ga$_{2}$O$_{3}$: A New Monoclinic form of Fe$_{2}$O$_{3}$

John S. Jamison; Brelon J. May; Julia I. Deitz; Szu-Chia Chien; David W. McComb; Tyler J. Grassman; Wolfgang Windl; Roberto C. Myers

doi:10.1021/acs.cgd.9b00029

paper

Ferromagnetic Epitaxial μ-Fe $_{2}$ O $_{3}$ on β-Ga $_{2}$ O $_{3}$ : A New Monoclinic form of Fe $_{2}$ O $_{3}$

arXiv:1901.04844 · doi:10.1021/acs.cgd.9b00029

Abstract

Here we demonstrate a new monoclinic iron oxide phase (μ-Fe $_{2}$ O $_{3}$ ), epitaxially stabilized by growth on (010) β-Ga $_{2}$ O $_{3}$ . Density functional theory (DFT) calculations find that the lattice parameters of freestanding μ-Fe $_{2}$ O $_{3}$ are within ~1% of those of β-Ga $_{2}$ O $_{3}$ and that its energy of formation is comparable to that of naturally abundant Fe $_{2}$ O $_{3}$ polytypes. A superlattice of μ-Fe $_{2}$ O $_{3}$ /β-Ga $_{2}$ O $_{3}$ is grown by plasma assisted molecular beam epitaxy, with resulting high-resolution x-ray diffraction (XRD) measurements indicating that the μ-Fe $_{2}$ O $_{3}$ layers are lattice-matched to the substrate. The measured out-of-plane (b) lattice parameter of 3.12 $\pm$ 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-Fe $_{2}$ O $_{3}$ layers with β-Ga $_{2}$ O $_{3}$ . Finally, DFT modeling predicts that bulk μ-Fe $_{2}$ O $_{3}$ is antiferromagnetic, while the interface region between μ-Fe $_{2}$ O $_{3}$ and β-Ga $_{2}$ O $_{3}$ leads to ferromagnetic coupling between interface Fe $^{3 +}$ cations selectively occupying tetrahedral positions. Magnetic hysteresis persisting to room temperature is observed via SQUID measurements, consistent with the computationally predicted interface magnetism.

19 pages and 7 figures

Ferromagnetic Epitaxial μ-Fe2​O3​ on β-Ga2​O3​: A New Monoclinic form of Fe2​O3​

Abstract

Ferromagnetic Epitaxial μ-Fe $_{2}$ O $_{3}$ on β-Ga $_{2}$ O $_{3}$ : A New Monoclinic form of Fe $_{2}$ O $_{3}$