Effect of Electroplating Parameters on Magnetic Properties of Ni-Co Alloys

Abstract

Relations between crystal structure, composition, and coercive force of Ni-Co, Ni-Co-P, and Co-P alloys have been reported. These relations are very useful for the understanding of the magnetic properties of Ni-Co alloys. However, their practical application is limited because the dependence between plating parameters and magnetic properties of the deposit were not established. In this paper, relations between magnetic properties and plating parameters of Ni-Co films varying in composition and thickness are reported. A relation between coercivity and stress of deposit is shown. The coercivity for a particular thickness of deposit and particular composition and concentration of solution increases from 130 to 250 Oe as the plating temperature increases from 25°C to 40°C, then the coercivity decreases as temperature increases from 40°C to 85°C. Similar relations have been found between magnetic properties and plating current density, Ni/Co ratio of solution (for various concentrations), and thickness. These results are reproducible and have been plotted. The effect of pH is also reported. With these experimental results, the optimum plating conditions for Ni-Co materials with coercivity ranging from 100–550 Oe can be found. Ni-Co alloy with 500 Oe coercivity was deposited on drums and bit density of 5000-flux reversals was obtained.