Magnetic Properties of Cobalt Ferrite (001) Films Grown on Spinel-Type Buffer Layers

To improve the interface magnetism of Co_xFe_3-xO₄ (CFO) films that are grown on MgO substrates and exhibit extremely large perpendicular magnetic anisotropy, we attempted to insert two different spinel-type oxides [CoCr₂O₄ (CCO) and MgTi₂O₄ (MTO)] between the CFO films and their MgO(001) substrates. Although both buffer layers were epitaxially grown on MgO(001), the CFO films grown on CCO/MgO(001) became polycrystalline with a significantly lower level of magnetization, while the magnetization of the CFO films on MTO/MgO(001) fell as a function of the thickness of the MTO layer. A secondary ion mass spectroscopy analysis revealed a remarkable interdiffusion of Co and Mg.