Giant magneto-impedance and its relaxation in Co–Fe–Si–B amorphous ribbons

Abstract

Systematic measurements of giant magneto-impedance (GMI) and its relaxation (magneto-impedance aftereffect) have been carried out in a series of Co-rich amorphous ribbons ranging in magnetostriction values from −3.5 to +3.5 ppm. The value of GMI is a maximum for the alloy with the lowest value of magnetostriction, corresponding to a maximum of the transverse permeability. The impedance relaxation between two fixed times depends on the magnetostriction constant (λs) of the samples, and the observed trend is consistent with the theories which predict a direct relationship of the conventional permeability aftereffect (MAE) with the square of λs. Furthermore, the variation of the impedance aftereffect with the driving current resembles the behavior of MAE, and a connection between both effects can be established.

The effect of magnetoelastic interaction on the GMI behaviour of Fe-, Co- and Co–Fe-based amorphous wires

“…The Co 72.5 Si 12.5 B 15 wire with large negative magnetostriction value (−2.6 × 10 −6 ) shows circular magnetisation and its domains are always circular structure (Bamboo domain structure). When Fe is partially substituted by Co in Co 72.5 Si 12.5 B 15 alloy, magnetostriction value changes [26] and it become nearly zero (∼0.08 × 10 −6 ) in (Co 94 Fe 6 ) 72.5 Si 12.5 B 15 alloys. Hence, the magnetoelastic energy of this material is very low and domains are not oriented in any preferential direction.…”

Relationship between the giant magnetoimpedance effect and the relaxation of magnetic permeability

“…4(b). The presence of magnetic after effect in amorphous wires has been previously reported in ribbons [4,5]. The Presence of MAE is usually ascribed to the rearrangement of the magnetic moments in the magnetically coupled grains [8].…”

“…According to the bibliography [2], typical values of parameters involved in such a dynamics goes to relaxation/resonance frequencies corresponding to a few MHz, reason because of this analysis can not be omitted in GMI experiences. In fact, there is in the bibliography a bit of information concerning to magnetic relaxation in amorphous samples, but the results are not conveniently related to GMI relaxation [3][4][5].…”

Magnetic after-effect of the giant magnetoimpedance in cobalt-based amorphous wires

“…In this work we study the time dependence of the complex impedance after a sudden change in the magnetic field. The existing number of works dealing with the time dependence of GMI in this materials are very reduced [4][5][6] although the consequences can be important. From the theoretical point of view MAE gives information about the dynamics of the material but also reveals a useful information about the stability and accuracy of these materials for technical applications in the field of sensors.…”