Giant magneto-impedance effect adjusted by electrolytic polishing and thinning of Co-based amorphous ribbons

Abstract

The giant magneto-impedance (GMI) effect of Co-based ribbons treated by using electrochemical polishing method has been investigated. The initial susceptibility (χi ) and the longitudinal GMI ratio (L-GMI) as a function of the polishing time (t poli) were measured and discussed. The L-GMI firstly increases and then decreases with the increasing of t poli. At t poli = 30 s, the maximum GMI of ∼270% is obtained. This L-GMI trend as a function of t poli is mainly attributed to the variation of effective magnetic anisotropy (H k,eff). The variation of H k,eff comes from the optimization of surface qualities as well as the thinning of the thickness. The thinning of the Co-based ribbons results in the changing of demagnetization effect and, more importantly, the variation in the residual stress distributions. The latter effect will strongly affect the magnetization conditions for the samples with longer t poli: stress variation here is dominant over the influence of surface qualities in the final GMI effect. Furthermore, another factor that may influence GMI is the current density variation related to thickness decrease. At the same time, reducing of stray fields, closely related to surface qualities, is the dominant factor affecting GMI for the samples with shorter t poli.