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

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. (C) 2002 Elsevier Science B.V. All rights reserved