Giant magnetoimpedance in layered FeSiB/Cu/FeSiB films

The giant magnetoimpedance (GMI) effect has been studied in layered FeSiB/C u/FeSiB films in the frequency range of 100 kHz-30 MHz. The field dependenc e of the GMI ratio shows that the GMI ratio increases with magnetic field H -a, reaching a positive maximum value at a certain field, and then graduall y decreases to negative values. For the layered films with a Cu film width of 0.6 mm, the positive maximum GMI ratio is about 2%, which is smaller tha n the value of the negative GMI ratio (-6.6% at H-a = 50 Oe) at a frequency of 5.2 MHz. With an increase of the Cu film width, a positive maximum GMI ratio of 4.5% and 13.5% is obtained for H-a = 30 Oe and 5.2 MHz in the laye red films with a Cu film widths of 1 and 1.3 mm respectively. In addition, all the layered films exhibit a large negative GMI ratio at a relatively la rge field and it is associated with the easy axis orientation of the layere d films. The increase of the positive maximum GMI ratio with an increase of Cu film width at 5.2 MHz may be due not only to the effect by the increase of Cu film width, but also to the difference in the easy axis orientations of the layered FeSiB/Cu/FeSiB films. (C) 2001 American Institute of Physic s.