Co-Ni-Cu/Cu multilayer films form one of the most promising electrodeposited systems for giant magnetoresistance applications. We have studied the surface roughness of Co-Ni-Cu/Cu multilayers with different total thickness and different layer thicknesses systematically by ex situ atomic force microscopy. Films for which the Cu deposition potential was −0.4 or −0.5 V relative to a saturated calomel reference electrode were significantly smoother than films for which the deposition potential was −0.2 V when the total film thickness was less than about 300 nm. For films grown on deliberately roughened substrates, a critical thickness at which the roughness changed from being substrate-dominated to being growth-dominated was identified.Ever since the first reports on the Fe/Cr system were published, 1,2 giant magnetoresistance ͑GMR͒ in magnetic metal multilayer films has been a topic of active investigation. Most studies were made using films deposited by vacuum-based methods, sputtering and molecular beam epitaxy, but electrodeposited GMR multilayers have also been studied intensively because they can be prepared at ambient temperatures and pressures using low-cost apparatus. 3 These features of electrodeposited multilayers make them potentially attractive for low-cost GMR applications. 4 Earlier studies have clearly demonstrated that the GMR of electrodeposited multilayers is linked to the exact values of deposition parameters such as electrolyte pH 5 and deposition potential, 6 and it has been widely assumed that this is because changes in the deposition parameters give rise to changes in the continuity of the magnetic and/or nonmagnetic layers and the interface roughness. For example, pinholes in the nonmagnetic layer can lead to ferromagnetic coupling between the magnetic layers, which destroys the GMR, and rough layers can also couple magnetostatically. However, despite their obvious relevance, there have been very few detailed structural studies of electrodeposited GMR multilayer films grown under different conditions 7 and even fewer that provide quantitative atomic force microscopy ͑AFM͒ data on the surface roughness. 8 Here we present such data for a series of electrodeposited Co-Ni-Cu/Cu multilayers with different repeat distances and different total thicknesses. The Co-Ni-Cu/Cu system is one which has been previously demonstrated to exhibit record GMR values. 3 We show for the first time how the roughness of electrodeposited multilayers depends on the initial roughness of the substrate and the deposition potential. We demonstrate that films for which the Cu deposition potential V Cu = −0.4 or −0.5 V relative to saturated calomel ͑SCE͒ are substantially smoother than those for which V Cu = −0.2 V for total film thickness less than about 300 nm. We further demonstrate that for multilayers grown on rough substrates, the roughness is dominated by the substrate roughness until a critical thickness t c is reached. This thickness is approximately that at which the roughness of a similar film grown on a smooth su...
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