Electrodeposition for obtaining homogeneous or heterogeneous cobalt-copper films

Direct electrodeposition of heterogeneous deposits may be an alternative method for preparing cobalt-copper coatings with magnetoresistive properties. Co-Cu electrodeposition was obtained in sulfate baths containing different citrate concentrations in order to prepare either homogeneous or heterogeneous Co-Cu deposits. X-ray diffraction (XRD) and voltammetric stripping analysis were used to study the kind of deposits formed. Citrate-free baths produced heterogeneous films, although dendritic growth was observed, thus increasing the deposit's thickness. Increasing the Cu(II)/Co(II) ratio in solution enabled the formation of smoother deposits. The presence of citrate at up to twice the total metallic concentration in the bath improved the morphological aspects of the deposits, their structural heterogeneity being maintained. Higher citrate concentrations induced the loss of heterogeneity, and both electrochemical and diffraction peaks tended towards single peaks. Homogeneous Co-Cu deposits, formed by a solid solution structure, were obtained in highly complexed citrate baths.