The effect of magnetic fields on the electroless deposition of Co–W–P film

Magnetic fields perpendicular to the copper substrate were applied during an electroless deposition process to obtain Co–W–P thin films from alkaline baths. Effects of different magnetic intensities, pH values and different powers of ultrasonic on the composition, microstructure and magnetic properties of Co–W–P alloys were investigated. Along with the increase of magnetic intensity, deposition speed and film thickness increased gradually as a result of the impacts of magnetic force and micro-MHD effect. Higher magnetic intensity could improve cobalt atomic percentage in the film and increase magnetization of Co–W–P films. Almost all of the deposited films were crystalline and contained hexagonal cobalt with a preferred crystallographic orientation (002). Dissimilar surface morphology could be detected under different pH values when 0.5 T magnetic intensity was introduced, such as rice-like and needle-like structures. When magnetic field was applied during the electroless deposition, grains of films tended to grow perpendicularly to the substrate and hill-like structures would appear with the increase of magnetic intensity. It was also found out that hill-like structure thin films tended to have high coercivities. Hill-like structures could be smoothed when ultrasonic was applied during magnetic electroless deposition. Maximum coercivity (914 Oe) could be obtained when 90 W ultrasonic and B = 0.5 T were introduced.