Anisotropy and domain patterns of flash stress-annealed soft amorphous and nanocrystalline alloys

Domain structures and stress-induced anisotropy in some soft ferromagnetic materials are reported. Stress-Joule heating performed on amorphous Co66Fe4B12Si16Mo2 induces an anisotropy perpendicular to the ribbon axis, as in nanocrystalline FeSiBCuNb alloys. However, in the case of FeZrB-Cu-Nb systems, large longitudinal domains are observed. We think that the origin of this anisotropy comes from the so-called back stress effect as previously proposed by Herzer. As magnetostrictions of both α-Fe and α-FeSi crystallites are negative, the frozen-in stress exerted on α-Fe nanograins is expected to be compressive-type. We suggest that this surprising behaviour is related to more pronounced creep because of the smaller hardness of α-Fe nanograins