Influence of Bath Composition on Magnetic Properties of Electrodeposited Co-Pt-W Thin Films

Effect of bath composition ([Co2+]/[PtIV] and [WO42-], [cit−]) and pH on the magnetic properties of electrodeposited Co-Pt-W thin films has been investigated. Electrodeposited Co-Pt-W thin films exhibited strong perpendicular magnetic anisotropy when the ratio of [Co2+] to [PtIV] was 10; cathode current efficiency and perpendicular magnetic anisotropy showed little variations when [WO42-] was lower than 0.1 mol/L, but perpendicular magnetic anisotropy had strengthened when [WO42-] was over 0.1 mol/L, which could be explained by the fact that the hydrogen evolution could produce pores as magnetic domain pinnings; citrate as complexing reagent can promote the polarization of [Co2+] and [PtIV]. As a result, the equilibrium electrode potentials of cobalt and platinum moved to negative direction, which led to the co-deposition of Co, Pt, and W. It was also found out that the as-deposited Co-Pt-W hard magnetic thin films were very homogeneous, smooth, and had the maximum coercivity for the bath pH 8.5 and the concentration of citrate 0.26 mol/L.