Study of Electrolyte pH in Production of Cu–Co–Ni Ternary Alloys and Its Effect on Microstructural and Magnetic Properties

Ternary Cu-Co-Ni alloys were electrodeposited in the mediums that have different pH levels to investigate the microstructuremagnetic relationship. The electrolyte pH was considered as high (4.2) and low (2.5) levels. For both levels, the anomalous codeposition occurred in the deposition of the alloys. The face centered cubic crystalline structure was observed in the ternary alloys grown at high and low electrolyte pH levels. In addition, a significant decrease in average grain size of the crystallites, from 60 to 21 nm, occurred when the pH was reduced from 4.2 to 2.5. A dendritic structure was detected in the surface of the alloy deposited from electrolyte with the high pH level, whereas the alloy grown at the low pH has a surface without dendritic clumps. According to magnetic analysis, an increase in the saturation magnetization, caused by the increase of Co content, was detected when the pH was reduced. The coercivity H_c levels were 89 and 80 Oe for the alloys grown at high and low pH, respectively. The change of H_c was attributed to the changes in microstructural properties, i.e., different average grain sizes of the crystallites and surface morphologies, occurred when the electrolyte pH changed. The anisotropic magnetoresistance (AMR) was exhibited by the alloys and the AMR ratio was enhanced from ~3% to ~3.5%-4% when the pH decreased.