Stress and/or field annealing of Fe 73.5Cu 1Nb 3Si 15.5B 7 amorphous ribbon

Abstract

The magnetic anisotropy induced by stress (500 MPa) and/or axial magnetic field (750 A/m) annealing in Fe 73.5Cu 1Nb 3Si 15.5B 7 amorphous alloy has been investigated. The thermal treatments were carried out using the current annealing technique (current densities ranging from 30 to 47 A/ mm 2 , duration of 120 s). A uniaxial in-plane magnetic anisotropy was induced in the samples as a result of these thermal treatments. The easy axis of this induced anisotropy at current densities <40 A/mm 2 was transverse (stress annealing (SA) and stress+field annealing (SFA)) or longitudinal (field annealing (FA)) to the ribbon direction. At current densities >40 A/mm 2 the easy axis is parallel to the axis of the ribbon for the three types of treatment. The dependence of this induced anisotropy on the current density has a maximum (1000 J/ m 3) around 40 A/ mm 2 , which we relate to the first stages of the crystallization process followed by a minimum at around 47 A/ mm 2 . Similar dependence was obtained for the coercivity of the samples after these thermal treatments. A coercivity of about 1 A/m has been achieved after magnetic FA.