A CoFe binary alloy film with 24 kG of saturation magnetic flux density, Bs, was prepared by electrodeposition. The Bs value of the CoFe alloy film prepared by electrodeposition from the conventional bath is usually equal to 21 kG. With the addition of trimethylamineborane, a well-known reducing agent, the Bs value was found to increase to 23 kG. Furthermore, with the use of a separated compartment dual cell system, a Bs value as high as 24 kG was reached. For obtaining the highest Bs, it was found to be essential to avoid the oxidation of ferrous ion to ferric ion in the plating bath. The coercivity, Hc, values were 15, 14, and 15 Oe for the films with 20, 23, and 24 kG of Bs, respectively. The key for obtaining high Bs materials is to avoid the oxidation of ferrous ions in the bath. In addition, it was found that the Hc value of 15 Oe for CoFe film with the highest Bs value of 24 kG could be lowered to 8 Oe by annealing in an applied magnetic field of 500 Oe.
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