High-frequency magnetic aftereffect in Co-based amorphous wires and ribbons

Abstract In this work, the magnetoimpedance relaxation in Co 68.25 Fe 4.5 Si 12.25 B 15 systems has been measured in the frequency interval 500 kHz–3 GHz. A comparison between ribbons, amorphous and glass-covered wires of nominal composition Co 68.25 Fe 4.5 Si 12.25 B 15 was made. The time variation of the calculated characteristic impedance after field removal displays a similar behavior to the classic magnetic permeability aftereffect measured at lower frequencies by means of conventional fluxmetric techniques. Thermal treatments are shown to affect the impedance relaxations in melt-spun alloys. Conversely, no substantial effect has been observed in glass-covered wires.