Fe$_3$O$_4$/ZnO: a high-quality magnetic oxide-semiconductor heterostructure

Magnetite (Fe$_3$O$_4$) is ranked among the most promising materials to use as a spin injector into a semiconducting host. We demonstrate epitaxial growth of Fe$_3$O$_4$ films on ZnO which presents a further step towards incorporation of magnetic materials into semiconductor technology. X-ray spectroscopy results evidence that the iron-oxide is phase-pure and nearly stoichiometric magnetite. Diffraction measurements indicate highly oriented epitaxy and almost complete structural relaxation. The microstructure consists of domains separated by anti-phase boundaries or twin boundaries as a result of island-like growth. The magnetic behavior shows a rather slow approach to saturation at high fields in comparison with bulk crystals, which is likely due to antiferromagnetic coupling at the anti-phase boundaries.