Optimization of the giant magneto-impedance effect in Fe₂₀Ni₈₀/Cu composite wires by Joule heating annealing

Giant magnetoimpedance (GMI) sensors are increasingly employed in modern magnetic sensing technologies. However, improving the GMI performance of magnetic cores remains challenging due to intrinsic limitations in material properties and structural stability. In this work, we explore the use of Joule heating to enhance the GMI response of Fe₂₀Ni₈₀/Cu composite wires. By applying a current of 1.8 A for 10 min, notable improvements in magnetic domain uniformity and a reduction in domain spacing are observed. Under these conditions, GMI ratios reach 1870% in the non-diagonal mode and 1147% in the diagonal mode, respectively, highlighting their potential for applications in high-precision weak magnetic field sensing.