Magnetic properties of cobalt ferrite (001) films grown on spinel-type buffer layers

In order to improve the interface magnetism of the Co_xFe_3-xO₄(CFO) films grown on MgO substrates that show extremely large perpendicular magnetic anisotropy, we attempted to insert two different spinel-type oxides of CoCr₂O₄ (CCO) and MgTi₂O₄ (MTO) between the CFO films and the MgO(001) substrates. Although both buffer layers were epitaxially grown on MgO(001), the CFO films on the CCO/MgO(001) became polycrystalline with a significantly lower magnetization. The magnetization of the CFO films on the MTO/MgO(001) decreased as a function of the MTO layer thickness. An SIMS experiment revealed an interdiffusion of Co and Mg. All the results indicate that other spinel-type buffer layers are required to improve the interface magnetism of the CFO(001) films. The promising spinel-type compound may not contain Mg .