Structural and magnetic characterization of electrodeposited Ni/Cu multilayers

Ni/Cu multilayers were electrodeposited from a single solution electrolyte by galvanostatic method. Interface roughness, magnetization and magneto-transport studies of Ni/Cu multilayers on Si(1 1 1)/Ti/Cu substrate were carried out for samples deposited from three different electrolytes, viz. pure sulphate, sulphate–citrate and sulphate-polyethylene glycol-8000 (PEG-8000). The top Ni-layer morphology of these samples was characterized by atomic force microscope (AFM). Detailed analysis of the morphological data showed a typical two-dimensional fractal growth pattern in all the three cases. The structural parameters like interface roughness, density and thicknesses of Ni and Cu layers were extracted from neutron reflectivity (NR) study. The order of interface roughness obtained from NR and AFM was found to be quite close. The sample deposited from sulphate–citrate electrolyte was found to have minimum interface roughness. The polarized neutron reflectometry (PNR) measurement showed reduced magnetic moment value (∼0.41 ± 0.01 μB) for nickel layers compared to bulk value in all the three samples. The magnetoresistance (MR) of these samples were measured at room temperature. An attempt has been made to explain the observed MR results in terms of granular structure and scattering mechanism involving super-paramagnetic and ferromagnetic particles in these samples.