Optimization of the Giant Magneto-Impedance effect in Fe₂₀Ni₈₀/Cu composite wires by joule heating annealing

Giant magneto-impedance (GMI) sensors are increasingly employed in modern magnetic sensing technologies. However, improving the GMI performance of magnetic cores remains difficult 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 Fe 20 Ni 80 /Cu composite wires. By applying a current of 1.8 A for 10 minutes, notable improvements in magnetic domain uniformity and a reduction in domain spacing were observed. Under these conditions, GMI ratios reached 1870% in the non-diagonal mode and 1147% in the diagonal mode, respectively, highlighting their potential for application in high-precision weak magnetic field sensing.