NiO/αFe2O3 multilayers prepared by PLD: a model system for magnetic study of interdiffusion

We prepared multilayer films based on NiO and αFe₂O₃ by pulsed laser ablation. In these NiO/αFe₂O₃ and αFe₂O₃ /NiO multilayers, interdiffusion leads to the formation of the nickel ferrite NiFe₂O₄ at the interfaces. Its ferrimagnetism provides a local probe on the admixture of the antiferromagnetic oxides NiO and αFa₂O₃ which is macroscopically measurable. We performed magnetization, torque and magneto-optical measurements on the multilayer samples. Surprisingly, an oscillation of the total magnetic moment m as a function of the number of interfaces was observed. The oscillation of m reverses when the succession of NiO/αFe₂O₃ layers is inverted to αFe₂O₃/NiO multilayers. This indicates a magnetic and structural nonequivalence of the NiO/αFe₂O₃ and the αFe₂O₃/NiO interfaces. This oscillation is observed in the magnetization, the Faraday effect and the coercive fields. Furthermore, Secondary Ion Mass Spectroscopy measurements (SIMS) on some NiO/αFe₂O₃ samples showed a well formed multilayer structure with pronounced interlayers. The presence of NiFe₂O₄ can be seen from transmission spectroscopy measurements which we performed on the αFe₂O₃/NiO multilayers series