Influence of the distance between two voltage contacts on giant magneto-impedance of Co-based amorphous wires

The Co75Fe4.2Si8B12Nb0.8 amorphous wires of 30μm in diameter are produced by melt extraction and annealing at 450℃ for 20 min in vacuum with a longitudinal or transverse field of 40 kA/m. Distances between the two voltage contacts of 6, 5, 4 and 2 mm are obtained by moving the two voltage contacts towards the centre of the sample at the same time. Results indicate that magneto-impedance response is dependent on the distance significantly. As distance decreases from 6 to 2 mm, AZ/Z reduces from 609% to 95% and giant magneto-impedance （GMI） profiles change from two-peak to single-peak. Besides, field sensitivity improves from 0.47%/（A/m） to 0.76%/（A/m） when the single-peak GMI just appears. It is therefore concluded that actual measurements can be made comparable only by taking into account the influence of distance between two voltage contacts for a magneto-impedance measurement.