Transverse domain structure related giant magnetoimpedance in nanocrystalline Fe73.5Cu1Nb3Si13.5B9 ribbons

A sensitive field- and frequency-dependent magnetoimpedance (MI) has been observed in nanocrystalline Fe73.5Cu1Nb3Si13.5B9 ribbons. A maximum value for the MI ration Delta Z/Z = [Z(H) -Z(H-max)]/Z( H-max), of more than 400% was obtained in these nanocrystalline ribbons (annealed for 3-5 h at 550 degrees C). A peak in the field dependence of the MI ratio Delta Z/Z was observed in nanocrystalline samples, but not in the as-quenched amorphous samples. The sensitivity attained a value larger than 60% Oe(-1) in the field range 3-7 Oe at 800 kHz for the nanocrystalline ribbons. Domain observation experiments show that the transverse domain structure observed in nanocrystalline samples is responsible for their giant MI effects, and the domain wall movements in the transverse domain pattern region are dominant during the initial magnetization processes in both longitudinal and transverse directions of the applied field. The correlation between the magnetization processes and the giant MI effects is discussed briefly based on the view of a modified skin effect. (C) 1998 American Institute of Physics. [S0021-8979(98)05322-5].