Electrodeposited Co-Fe and Co-Fe-Ni alloy films for magnetic recording write heads

The electrodeposition of Co-Fe and Co-Fe-Ni alloys from electrolytes without any organic additives is explored. For Co-Fe alloys, the effect of the ratio of Co and Fe concentrations in the electrolyte on the composition and magnetic properties of the deposits is examined. A maximum saturation magnetization of 20.4 kG is obtained, however the films showed high coercivity (20 to 30 Oe). The addition of Ni to the solution leads to much improved soft magnetic properties. A Fe-rich alloy, Co₁₉Fe₅₂Ni₂₉ showed a saturation magnetization of 20.5 kG, a coercivity of about 1 Oe and saturation magnetostriction λ_s, about 10^-6. Best soft magnetic properties are obtained when BCC and FCC phases are seen to coexist. The films show good stability of magnetic properties upon easy axis annealing up to 200°C. Magnetic force microscopy showed the domain pattern to be a ripple structure for films with positive magnetostriction, changing to a stripe domain structure with increasing Ni content. This corresponds to a change in sign of the magnetostriction