On the basis of our work on electroless CoB soft magnetic films with high saturation magnetization (Ms) and low coercivity (He) the effects of applying an external field during deposition and of adding Fe to the CoB binary system were investigated in order to improve the soft magnetic properties. When an external field (560 G) is applied, the He of deposited CoB films decreases from 1.20 Oe to 0.64 Oe. In the case of CoFeB ternary alloy films, FeSO4 is added to the CoB bath and its concentration is varied from 0.001 to 0.05 mol dm–3. The best soft magnetic properties, He = 0.72 Oe and Ms = 1180 emu cc, are obtained when the film is deposited from the bath containing 0.0025 mol dm3 of FeSO4. The film had a small magnetostriction value (–4.4 x 10 7) and higher permeability. The results of structural analysis suggest that the film consists of fine–particulated hexagonal close–packed crystallite with high crystallinity.
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