NiO//spl alpha/Fe/sub 2/O/sub 3/ multilayers prepared by PLD: a model system for magnetic study of interdiffusion

We prepared multilayer films based on NiO and /spl alpha/Fe/sub 2/O/sub 3/ by pulsed laser ablation. In these NiO//spl alpha/Fe/sub 2/O/sub 3/ and /spl alpha/Fe/sub 2/O/sub 3//NiO multilayers, interdiffusion leads to the formation of the nickel ferrite NiFe/sub 2/O/sub 4/ at the interfaces. Its ferrimagnetism provides a local probe on the admixture of the antiferromagnetic oxides NiO and /spl alpha/Fa/sub 2/O/sub 3/ 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//spl alpha/Fe/sub 2/O/sub 3/ layers is inverted to /spl alpha/Fe/sub 2/O/sub 3//NiO multilayers. This indicates a magnetic and structural nonequivalence of the NiO//spl alpha/Fe/sub 2/O/sub 3/ and the /spl alpha/Fe/sub 2/O/sub 3//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//spl alpha/Fe/sub 2/O/sub 3/ samples showed a well formed multilayer structure with pronounced interlayers. The presence of NiFe/sub 2/O/sub 4/ can be seen from transmission spectroscopy measurements which we performed on the /spl alpha/Fe/sub 2/O/sub 3//NiO multilayers series.