Magnetic properties of corrosion-resistant CoW films

CoW films with different compositions have been prepared by an electrochemical deposition method. The tungsten contents in the CoW films are controlled by adjusting electrolyte concentrations, pH values, and applied potentials. The magnetic and corrosion-resistant properties of the CoW films are systematically studied. With an increase in tungsten content and annealing temperature, the CoW films shift from in-plane magnetic anisotropy to magnetic isotropy, which is due to the formation of a hexagonal close packed (hcp) Co3W phase confirmed by morphological and phase evolutions. The magnetic properties of the CoW films remain stable even after immersion in a 0.5% NaCl solution for 170 hours. An ultrathin tungsten oxide passivation layer coated on the surface of the films protects the CoW films from corrosion.