Growth, structure, and magnetic properties of γ-Fe2O3 epitaxial films on MgO

Single-crystal epitaxial thin films of $\mathrm{\gamma -}{\mathrm{Fe}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ (001) have been grown on MgO(001) using oxygen-plasma-assisted molecular beam epitaxy. The structure and magnetic properties of these films have been characterized by a variety of techniques, including reflection high-energy electron diffraction (RHEED), low-energy electron diffraction (LEED), x-ray photoelectron spectroscopy and x-ray photoelectron/Auger electron diffraction (XPD/AED), vibrating sample magnetometry, and ferromagnetic resonance. Real-time RHEED reveals that the film growth occurs in a layer-by-layer fashion. The $\mathrm{\gamma -}{\mathrm{Fe}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ (001) film surface exhibits a (1×1) LEED pattern. The growth of $\gamma$ -Fe${}_{\mathrm{2}}$ O${}_{\mathrm{3}}$ films at 450 $°$ C is accompanied by significant Mg outdiffusion. AED of Mg KLL Auger emission reveals that Mg substitutionally incorporates in the $\mathrm{\gamma -}{\mathrm{Fe}}_{\mathrm{2}}{\mathrm{O}}_3$ lattice, occupying the octahedral sites. Magnetic moments are $\sim$ 2300 G and $\sim$ 4500 G for $\mathrm{\gamma -}{\mathrm{Fe}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ films grown at 250 °C and 450 °C, respectively. The high magnetic moment for the films grown at 450 °C could be attributed to the high degree of structural order of the films and Mg substitution at octahedral sites.