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

Abstract 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.