Preparation and Magnetic Properties of Fe₃O₄/MO(M=Ni, Co) Superlattices

The structural, electric and magnetic properties of (100)-oriented Fe₃O₄/NiO and Fe₃O₄/CoO superlattices on MgO(100) have been studied. The films were prepared by an activated reactive evaporation method. The lattice constants of each layers were a little changed from the bulk values due to a lattice mismatch with the substrate. The Fe 2p XPS of both Fe₃O₄/NiO and Fe₃O₄/CoO interfaces suggested the formation of stoichiometric Fe₃O₄. The saturation magnetizations (Ms) of Fe₃O₄/MO superlattices were compared with that of a Fe₃O₄ thin film as a function of the thickness of MO layers. The reduction in Ms of Fe₃O₄/NiO could be linked with the large exchange coupling with NiO. While the increase in Ms of Fe₃O₄/CoO was probably caused by the ferromagnetic coupling of the CoO interface with the Fe₃O₄ layer.