Magnetic properties and domain structures in stress-annealed FeZrB-(Cu)-(Nb) nanocrystalline ribbons

Abstract

Magnetic properties of nanocrystalline FeZrB-(Cu)-(Nb) compared to FeSiBCuNb are reported. Observations of domain patterns by magneto-optical Kerr effect (MOKE) method presented herein highlight qualitatively the incidence of stress-annealing on the induced anisotropy in soft magnetic materials. Transverse fine domains found in FeSiBCuNb alloys are consistent to a magneto-elastic interpretation of the stress-induced anisotropy. Nevertheless, it is not the case for FeZrB-(Cu)-(Nb) family where we observe a pronounced longitudinal induced anisotropy. According to the so-called “back stress effect” advanced by Herzer, the negative of bcc α-Fe grains, as well of bcc α-FeSi grains, should yield transverse anisotropy. Nowadays, this surprising feature is not still clear. For a technical standpoint, stress-induced anisotropy is interesting for new magnetic components in power electronics.