Influence of Cu deposition potential on the giant magnetoresistance and surface roughness of electrodeposited Ni-Co/Cu multilayers

摘要

It has been shown previously for electrodeposited Co/Cu multilayers that thesingle-bath electrodeposition process can be optimized from an electrochemicalpoint of view in order to avoid unwanted Co dissolution and incorporation of Coin the non-magnetic layer during the Cu deposition pulse. In the present work,electrodeposition of Ni-Co/Cu multilayers has been studied to clarify if thesame optimization method is appropriate when two magnetic elements are presentand if this potential results in the largest giant magnetoresistance (GMR) forthe particular alloy system studied. For this purpose, several Ni-Co/Cumultilayers were prepared by varying the deposition potential of the Cu layer.The composition analysis of the deposits showed that the Ni:Co ratio exhibits aminimum as a function of the Cu deposition potential, which can be explained byconsidering both the dissolution of Co and the mass transport of the reactants.Both the saturation GMR value and the intensity of the satellite peaks in theX-ray diffractograms were highly correlated with the resulting surfaceroughness of the deposits which was strongly varying with the Cu depositionpotential. Higher GMR values, lower saturation fields and more perfectmultilayer structure were observed for sufficiently positive Cu depositionpotentials only which enabled a partial Co dissolution resulting in a reducedsurface roughness. The results draw attention to the complexity of theoptimization procedure of the deposition of multilayers with several alloyingcomponents.