Effects of hypophosphite contents and surface treatment on electroplated Co-Ni-P thin films

This article describes the effects of sodium hypophosphite (hypo) content in cobalt nickel sulfate bath, and the duration of surface treatment prior to electroplating, on the magnetic, structural, and electrical properties of Co-Ni-P thin films. The coercivity of the Co-Ni-P layer can be controlled independently either by hypo content or by surface treatment. Transmission electron microscopy microstructure indicates that the width of grain boundaries of Co-Ni-P films is influenced by hypo in the magnetic bath. The mechanism of the coercivity increase by hypo in the bath is thought to result from magnetostatic or exchange decoupling at phosphorus-rich grain boundaries. Effects of these factors on media noise can be well-explained by the microstructural change of Co-Ni-P layers.