STUDY OF THE INTERDIFFUSION AT THE INTERFACES OF NIO ALPHA-FE2O3 MULTILAYERS PREPARED BY PULSED-LASER DEPOSITION/

We prepared NiO/alpha Fe2O3 multilayer films by pulsed laser ablation. Interdiffusion leads to the formation of the nickel ferrite NiFe2O4 a t the interfaces. Its ferrimagnetism provides a local probe on the adm ixture of the antiferromagnetic oxides NiO and alpha Fe2O3 which is ma croscopically measurable. We performed magnetization, torque and magne tooptical measurements on the multilayer samples. Several phenomena we re observed. As a function of the substrate temperature a kinetically (due to the incoming particle energies) and a thermally activated regi me of NiFe2O4 formation were observed. In the thermally activated regi me, the duration of the deposition per layer and therefore the tempera ture dependent diffusion at the interfaces plays a crucial role to the formation of the ferrite as can be seen from the magnetic moment m wh ich tends to saturate for long in-situ annealing times. Surprisingly, an oscillation of m as a function of the number of interfaces was obse rved for the NiO/alpha Fe2O3 multilayer films. This indicates a magnet ically and perhaps structurally non equivalence of the NiO/alpha Fe2O3 and the alpha Fe2O3/NiO interfaces. This oscillation is observed in t he magnetization, the Faraday and the coercive fields. (C) 1998 Elsevi er Science Ltd.