Electrodeposited Co-Ni films: Electrolyte pH-property relationships

Abstract

The effect of electrolyte pH on structural, magnetic, and magnetoresistive properties of Co-Ni films was studied. The films were deposited on a titanium substrate from the electrolytes with 4.10 +/- 0.05, 3.14 +/- 0.05, and 2.14 +/- 0.05 pH values. The Co-Ni system exhibited anomalous codeposition. Structural analysis indicated that the films had (220) preferential oriented face-centered cubic structure and their surface became smoother as the electrolyte pH decreased. The compositional and magnetic analysis revealed that an increase of the Co content in the films resulted in an increase in saturation magnetization and coercivity. Magnetoresistance curves indicated that the films show anisotropic magnetoresistance. Longitudinal and transversal magnetoresistances were found to be the highest values of 8 % and 7 %, respectively, for the film deposited at a low electrolyte pH. The variation of the Co:Ni ratio in deposits caused by the change of the electrolyte pH has a considerable effect on the properties of the films.