Glass removal and pulse current annealing effects on GMI properties and stability of Co-based amorphous microwires

The Giant Magnetoimpedance (GMI) effect in Co-based amorphous microwires (AMWs) has garnered significant attention for its potential in high-sensitivity, low-cost magnetic sensors. In this study, Co_69.25Fe_4.25Si₁₃B_12.5Nb₁ microwires prepared via the Ulitovsky–Taylor method were investigated to assess the effect of glass coating/removal and square-wave pulse current (SWPC) annealing on the GMI properties and long-term impedance drift stability. The GMI ratio was analyzed using definitions based on both zero-field and maximum-field (±50 Oe) conditions. Removing the inherent glass coating enhances the lower frequency (1–2 MHz) GMI sensitivity by releasing internal stress and decreased magnetoelastic anisotropy. and also improved impedance drift stability. SWPC annealing at 107 mA further enhanced the low-frequency GMI ratio and led to notably faster drift stabilization compared with as-prepared microwires. This improvement attributes to structural relaxation that lowers energy barriers for magnetic structure rearrangement. These findings highlight the critical role of post-processing techniques in tailoring GMI sensitivity and impedance drift stability, offering a pathway for developing robust, high-performance GMI sensors for weak magnetic field detection.