Defect and Interfacial Structure of Heteroepitaxial Fe₃O₄/BaTiO₃ Bilayers

Abstract The defect and interfacial structure in a Fe₃O₄/BaTiO₃ heteroepitaxial bilayer was investigated by scanning transmission electron microscopy. The results show that the Fe₃O₄ film grew epitaxially on BaTiO₃. The orientation relationship between Fe₃O₄, BaTiO₃ and MgO is [100]_{Fe₃O₄}//[100]_{BaTi₃O}//[100]_MgO and (010)_{Fe₃O₄}//(010)_{BaTiO₃}//(010)_MgO. An initial interfacial nucleation layer was formed that partially accommodated the lattice mismatch strain between BaTiO₃ and MgO. This investigation indicates that the formation of this buffer layer provides a high-quality BaTiO₃ surface for subsequent Fe₃O₄ growth, resulting in a semicoherent interface. The Fe₃O₄ surface is nearly atomically abrupt (roughness R_rms = 0.78 nm). The Fe₃O₄ film exhibits magnetic domains with a diameter in the range of 0.4–2 μm.