Epitaxial growth of CO0.75Fe2.25O4/NiO bilayer on MgO(001) substrate

In order to suppress the dead layer and improve the magnetic properties at the interface of the Co_xFe_3-xO₄ (CFO)/MgO(001), we investigated the effect of an insertion layer of NiO on the magnetization of CFO films. We succeeded in growing high-quality CFO films with perpendicular magnetic anisotropy (PMA) on NiO(001) buffer layers. Similar to CFO/MgO(001) films, a magnetic dead layer with a thickness of ~5 nm was observed. We conclude that the main cause for formation of the dead layer in CFO/MgO(001) is not Mg diffusion but in all probability the formation of anti-phase boundaries (APBs). Our results suggest that clarification of the dead layer formation in CFO films requires more detail of the interface structures, especially regarding the density of APBs.