Magnetic-field-induced anisotropies and exchange softening in Fe-rich nanocrystalline soft magnetic alloys

Realization of a high-saturation magnetization comparable to that of Fe–Si steel in advanced Fe-rich nanocrystalline soft magnetic alloys is potentially a very effective approach to reducing the emission of greenhouse gasses. This potential has stimulated recent research on the development of new alloys with exceptionally high Fe concentrations. However, some nanocrystalline soft magnetic alloys at the Fe-richest compositions exhibit unexpectedly large values of field-induced magnetic anisotropy (Ku ∼ 100 J m−3) which have a detrimental effect on the exchange-softening process in the nanostructures. Our viewpoint is that much attention must be paid to the induced anisotropies in order to utilize the full potential of the exchange-softening effect in Fe-rich nanocrystalline alloys. Possible origins of the large Ku value and the approach to suppressing the field-induced effect on Ku are discussed.