Structural, magnetic, and mechanical properties of electrodeposited cobalt–tungsten alloys: Intrinsic and extrinsic interdependencies.

Abstract: The mapping of structural, magnetic, and mechanical properties of Co–W coatings galvanostatically electrodeposited from a citrate–borate bath is investigated. The intrinsic characteristics of the coatings, such as crystallite size or tungsten content are correlated with the extrinsic growth parameters, such as pH, complexes distribution, and current density. The increase in pH from 5 to 8 results in an increase of the W content in the deposits from 2at.% up to 36at.% in a controlled way, and it correlates with an increase in concentration of W(VI) complexes in the bath. The crystallite size estimated from XRD patterns, decreases from 39 to 5nm with increasing W content from 3 to 25at.% respectively. The obtained coatings show highly tunable mechanical and magnetic properties. The hardness increases with W content from ∼3GPa up to ∼13GPa. A semi-hard ferromagnetic behavior with a coercivity of ∼470Oe along the perpendicular-to-plane direction is observed for Co–W alloys containing small amounts of W in the range of ∼2–3at.%. At higher tungsten contents the coatings are magnetically softer, and the electrodeposits become non-ferromagnetic beyond ∼30at.% W. Because of this combination of physical properties, electrodeposited Co–W coatings may become suitable materials for multi-scale technologies. [Copyright &y& Elsevier]