Electrodeposition and characterization of soft, high moment iron-cobalt-nickel thin film alloys for magnetic recording heads

The purpose of the research work outlined in this dissertation is to gain a better understanding of the relationship among deposition conditions, film composition, microstructure and the magnetic properties of Fe-Co-Ni thin film alloys. Fe-Co-Ni alloys are strong candidates for application in high density magnetic recording heads due to their high saturation magnetization and low coercivity. Soft, high moment Fe-Co-Ni films were grown by both direct current and pulsed-current electrodeposition. Structural and magnetic measurements were performed on these films revealing that soft magnetic properties in FeCoNi were obtained through the reduction of the grain size to dimensions smaller than the ferromagnetic exchange length. Reduction of the grain size was achieved by the competitive nucleation and growth of BCC and FCC phases under favorable conditions. The effect of various underlayers (nonmagnetic, ferromagnetic and antiferromagnetic) on film properties was investigated. Ferromagnetic underlayer can improve the magnetic alignment of FeCoNi, resulting in a smaller anisotropy dispersion and better overall magnetic properties. The high frequency performance of these materials becomes increasingly important for the advanced heads, which need to operate at extremely high frequencies, in excess of 1 GHz. Therefore, the high frequency behavior of Fe-Co-Ni thin films was studied. Magnetic results were complemented by an investigation of the corrosion resistance and mechanical properties of the alloys, of importance for the reliability and processing of these materials.