Study on preparation of Co–Pt–W alloy films by electrodeposition

Abstract

Co–Pt–W alloy films were prepared by the electroplating method to replace costly sputtering on a copper substrate. Effects of different pH values and current densities on composition, microstructure and magnetic properties of films were investigated. With the rise in pH values, the amounts of tungsten and cobalt decrease simultaneously as a result of less tungstate oxides in higher OH– concentration solution. Almost all the deposited films were crystalline and formed fcc CoPt(111) and hcp CoPt(002). Co–Pt–W alloy films intend to change from fcc to hcp structure when the current density was >20 mA cm⁻². It was found that hcp structures of Co–Pt–W alloy films possess high coercivity performance. Moreover, higher pH values induced lower saturation magnetisation while higher current densities could result in larger saturation magnetisation. Dissimilar surface morphology could be detected under different current densities. With increasing the current density, grains of films tend to agglomerate and grow perpendicularly to substrate. Bigger agglomerated particles and ‘hill-like’ structure could be observed when the current density was up to 30 mA cm⁻².