Electroplated Fe-Pt thick films prepared in plating baths with various pH values

Abstract

Fe-Pt thick-films were electroplated on a Ta substrate using a direct current, and the effect of the pH value of the plating bath on the magnetic properties of the films was evaluated. For the films prepared from the baths with the same bath composition, the Fe composition and the thickness increased with increasing the pH value. In order to remove the effect of the change in the film composition on the magnetic properties, we controlled the film composition at approximately Fe50Pt50 or Fe60Pt40 by the change in the amount of the iron sulfate. The remanence of the annealed Fe60Pt40 films did not depend on the pH value clearly, and showed almost constant value of 0.75 T. We obtained the large coercivity of approximately 460 kA/m in the pH value from 4 to 7. Since the Fe52Pt48 film prepared at pH ≈ 4 shows much higher (BH)max value of 70 kJ/m3 than that of 57 kJ/m3 for our previously-reported Fe50Pt50 film (pH ≈ 2), we concluded that slight higher pH value than not-adjusted one (pH ≈ 2) is effective to increase the coercivity.