FeCo-based soft magnetic alloys with high Bs approaching 1.75 T and good bending ductility

Fe-rich amorphous alloys with FeCo contents above 85 at% were formed by partial replacement of Fe by Co in Fe-Si-B-P alloy system. The resulting alloys exhibit good soft magnetic properties and bending ductility after stress relief annealing. Moreover, the maximum magnetic flux density (Bs) approaches 1.75 T, which is higher than those for previous reported Fe-rich Fe-metalloid alloys. Thus, the partial substitution of Fe by Co caused both Curie temperature (TC) and Bs exceeding those for the Fe-Si-B-P alloys. Any compositional modification so as to raise TC was found to be effective for the further increase in the previous maximum value of Bs for the Fe-metalloid amorphous alloy system reported to date. Based on this concept, it is expected that further high Bs exceeding largely 1.75 T is obtained for Fe-based soft magnetic alloys with higher total ferromagnetic element content.