Scanning of nickel sulfamate concentration in electrodeposition bath used for production of Ni–Co alloys

The Ni–Co films were produced by using the electrodeposition technique from the electrolytes with different Ni(SO₃·NH₂)₂·4H₂O concentrations (from 0 to 0.45 M). The Ni content of the films changed gradually from 0 to 57 %. The Ni–Co system exhibited anomalous codeposition. For 0 at.% Ni content, the saturation magnetization, M_s of the film was found to be 1298 emu/cm³, which is close to that of bulk Co (1420 emu/cm³). As the Ni content increased, M_s decreased since the M_s value of bulk Ni (480 emu/cm³) is lower than that of bulk Co. The coercivity, H_c, of Co film was found as 37 Oe. When the Ni content increased to 6 at.%, the H_c value dramatically increased to 109 Oe. The hexagonal closed packed (hcp) structure was observed for the films containing 0 and 6 at.% Ni. When the Ni content increased to 25 at.%, a mixed phase of face centered cubic (fcc) and hcp structure (mostly fcc) was detected. For further increase in Ni content (39 and 57 at.%), the peaks which occurred from the reflections of fcc phase were obtained. As a result of structural analysis, the Co content can be determined as 62–64 at.% for changing of crystal structure. The transfiguration from spherical granular to acicular surface morphology occurred around 75 at.% Co content. Magnetoresistance of the films was measured and it was found that the films show anisotropic magnetoresistance.