Epitaxial growth of ferromagnetic Fe₄N thin films on SrTiO ₃(001) substrates by molecular beam epitaxy

We have grown γ'-Fe₄N thin films on SrTiO ₃(STO)(100) and MgO(100) substrates by molecular beam epitaxy. From the ω scan X-ray diffraction measurement for the γ'-Fe ₄N(200) plane, the α-axis of γ'-Fe₄N grown on STO(100) was found to be perpendicular to the substrate. In contrast, the a-axis was inclined to the surface normal for γ'-Fe₄N formed on MgO(100). The saturation magnetization of γ'-Fe₄N/STO(100) deduced from the magnetization versus magnetic field curve was approximately 1900 emu/cm³ which is higher than that of bulk γ'-Fe ₄N value of 1400 emu/cm³.