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

To improve the interface magnetism of Co
_x
Fe
_3-x
O
₄
(CFO) films that are grown on MgO substrates and exhibit extremely large perpendicular magnetic anisotropy, we attempted to insert two different spinel-type oxides [CoCr
₂
O
₄
(CCO) and MgTi
₂
O
₄
(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.