Enhancing GMI properties of melt-extracted Co-based amorphous wires by twin-zone Joule annealing

► GMI effect is closely related to annealed microstructures observed by HRTEM. ► Twin-zone Joule-heated annealing (TJHA) as a novel effective annealing treatment. ► TJHA wires have relatively larger GMI ratio and field sensitivity. ► From HRTEM perspective to explain the GMI peaks feature of different states wires. ► TJHA wires are useful for high-resolution magnetic sensor applications.