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.
Highlights
For applying the thick-film magnets into commercial small-size devices, high economic viabilities of fabrication processes of the magnet are required, such as high deposition rate and simplicity of fabrication equipment
The remanence did not depend on the pH value clearly, and showed almost constant value of 0.75 T
With increasing pH value from 2 to 4, the coercivity increased and the chemical species of H2[C4H4O6] decreased. This tendency shows good agreement with the result for the citric acid. These results suggest that the complete dissociation of the complex agents, such as citric acid and tartaric one, is one of important factors to obtain the Fe-Pt thick-film magnet with high coercivity, and we found that a slight higher pH value than not-adjusted one is effective to increase the coercivity for the Fe50Pt50 and Fe60Pt40 films
Summary
For applying the thick-film magnets into commercial small-size devices, high economic viabilities of fabrication processes of the magnet are required, such as high deposition rate and simplicity of fabrication equipment. Chemical processes such as electroplating methods are preferred over physical one, such as sputtering, PLD (Pulsed Laser Deposition), and arc deposition methods. We reported Fe-Pt thick-film (≈ 20 μm) prepared in a plating bath containing citric acid, and showed their good hard magnetic properties.[12]
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