Giant magneto-impedance effect in nanocrystalline ribbons

Results on the GMI response of Fe73.5Cu1Nb3,Si13.5B9, Fe90Hf7B3, and Fe90Zr 7B3 nanocrystalline ribbons are reported. The obtained results are compared with those obtained for CoFeSiB amorphous ribbons, using the MI ratio, def ined as Delta Z/Z = [Z(H-dc = 0) - Z(H-dc = 1 kA.m(-1))]/Z(H-dc = 0). The m ast sensitive GMI response is given by Fe90Zr7B3 nanocrystalline ribbons - about 30%. A sensitivity of about 25% has been observed in Fe90Hf7B3 nanocr ystalline ribbons, which is comparable to that of CoFeSiB amorphous ones, w hile for Fe73.5Cu1Nb3,Si13.5B9 ones the maximum MI ratio reaches only 10%. The results are explained in terms of differences in the electrical resisti vities of the samples investigated as well as by taking into account the lo cal anisotropy distributions in each case. One of the main goals of this pa per is to discuss the role of good soft magnetic properties on the magnitud e and sensitivity of the GMI effect. (C)1999 Acta Metallurgica Inc.