Electroplating of Nanocrystalline CoFeNi Soft Magnetic Thin Films from a Stable Citrate-Based Bath

CoFeNi alloys are some of the most studied soft magnetic materials because of their superior properties over FeNi alloys as write head core materials in hard-disk-drives. Electroplating processes have major significance in the fabrication of thin-film recording heads due to their advantages of simplicity, cost-effectiveness, and controllable patterning. Conventional low pH (2.5-3.0) baths suffer from problems such as poor stability, low current density efficiency, and voids in deposited films due to the electroplating of hydrogen. A new, stable citrate-based bath has been developed in this study. Citrate can effectively improve the stability of CoFeNi plating baths, and denser CoFeNi films can be plated out because of the higher bath pH (>5). The effects of bath composition and plating conditions on the electroplating of CoFeNi thin films have been studied. CoFeNi thin films with preferred composition, mixed fcc-bcc phases, and 10-20 nm grain sizes have been plated out from the new citratebased bath.