Defect and Interfacial Structure of Heteroepitaxial Fe3O4/BaTiO3 Bilayers

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 mu m.