Magnetic properties and magneto-impedance of cold-drawn permalloy-copper composite wires

The permalloy-copper composite wires consisting of high conductivity Cu inn er core and NiFe outer shell were fabricated by a modified cold-drawn techn ique. The diameter of the Cu inner core was in 20-120 mu m range, and the N iFe outer shell was 10-40 mu m thick. The composite wires exhibit soft magn etic behavior and the giant magneto-impedance effect. The amplitude of the giant magneto-impedance at high frequencies is comparable to that of conven tional amorphous wires and significantly larger than that of NiFe wires wit hout Cu inner core. Nevertheless, the sensitivity of these wires does not r each the theoretical predictions based on the simple models for composite w ires with the axial or circumferential types of magnetic anisotropy.