Magnetoresistive granular Cu–Co–Ni coatings prepared by electrodeposition

Electrodeposition of Cu–Co–Ni coatings was performed from slightly acidic citrate–sulphate solutions. Bath composition and deposition potentials were varied in order to prepare copper-rich ternary coatings with different metal percentages. Low copper (II) and high nickel (II) concentrations were necessary to attain uniform non-dendritic electrodeposits with Co + Ni percentages between 10 and 30 wt%. Low magnetoresistive values were detected for as-deposited samples containing Co + Ni percentages around 25 wt%, although X-ray diffractograms showed miscibility of the three metals. The annealing of the samples at different temperatures led to granular coatings with the magnetoresistive values increase, as a consequence of the ferromagnetic metals segregation from within the non-magnetic matrix. Magnetic Force Microscopy (MFM) technique made possible to detect changes on the magnetic response between as-deposited and annealed samples.