Influence of nanocrystallization on the magneto-impedance effect in FeCuNbSiB amorphous wires

The evolution of the giant magneto-impedance effect (GMI) in the Fe/sub 73.5/Si/sub 13.5/B/sub 9/Cu/sub 1/Nb/sub 3/ amorphous alloy wire as a function of the structural and magnetic changes induced by suitable thermal treatments are reported here. The results show that the maximum GMI relative changes and magnetic field sensitivity are observed after annealing in the range of temperatures T/sub a/=550-600/spl deg/C, where nanocrystallization occurs. This maximum effect is related to the optimum compromise between soft magnetic behaviour and electrical properties, i.e. maximum circular susceptibility and minimum resistivity.