Electrodeposited Fe–Ni Films Prepared in a Citric-Acid-Based Bath with Different pH Values

We plated Fe-Ni films from a citric-acid-based plating bath and evaluated the effect of pH value in the bath on the magnetic properties and the productivities of the films. In this study, the pH value of the bath was controlled from 0.5 to 3.6 by the addition of hydrochloric acid or sodium citrate. The electrodeposited Fe-Ni film with the Fe content of approximately 22 at.% prepared at high pH (>3) tends to show large coercivity (> 100 A/m), rough surface and relatively high cathode efficiency (>70%) whereas the films prepared at low pH (1) tend to show low coercivities (<; 50 A/m), smooth surfaces and low cathode efficiencies (60%). The Fe
₂₂
Ni
₇₈
film prepared from the bath without the pH adjuster of a hydrochloric acid or a sodium citrate shows low coercivity of 25 A/m, smooth surface and relatively high cathode efficiency of 65%. Since low coercivity, smooth surface and high cathode efficiency are important factors for mass-producing Fe-Ni films, we concluded that a citric-acid-based bath with pH range from 1 to 3 is suitable for electrodeposition of soft magnetic Fe-Ni films.