Magnetic properties of multilayer BaTiO3/NiFe2O4 thin films prepared by solution deposition technique

In this work multilayered structures, composed of perovskite BaTiO3 and spinel NiFe2O4 layers, were obtained by solution deposition technique. The multiferroic films with different geometries, i.e. different numbers and thicknesses of titanate and ferrite layers, were prepared. Structural characterization of the sintered thin films confirmed the well-defined layered structure with overall thickness around 500 nm, crystalline nature of perovskite BaTiO3 and spinel NiFe2O4 phases without secondary phases (after sintering at 750 degrees C) and grains on nanometer scale. It was also shown that there are no significant changes of the film microstructure with variation of the layer geometry. The influence of the film geometries on magnetic properties of the multiferroic films sintered at 750 and 900 degrees C were also investigated. The well saturated hysteresis loops with low coercitivity, typical for nickel-ferrite based materials, were recorded. It was shown that the saturation magnetization decreased with decrease of the titanate and ferrite layer thicknesses (i.e. increased amount of their contact surfaces). It is believed that the observed magnetic behaviors are mainly influenced by the interlayer straining, whereas contribution of the microstructural differences is not so pronounced.