Magnetic properties and giant magnetoimpedance of nanocrystalline Fe92-xZr7BxCu1 ribbons

The influence of substitution of B for Fe on the microstructure, magnetic properties, and giant magnetoimpedance (GMI) effect has been studied for the nanocrystalline soft magnetic ribbons Fe92-2Zr7BxCu1 (x=2,4,6,8,10) annealed at 873 K for 20 min. The experimental results show that the thermal stability of the amorphous precursor is enhanced and the body-centered-cubic phase grains become smaller with increasing B content. The coercive force H-c exhibits a minimum of 2.51 A/m for the ribbon with x=8, where the effective permeability reaches the maximum. The frequency and field dependence of GMI effect is very sensitive to B content. For the ribbon with x=8, The maximal GMI ratio (Delta Z/Z)Delta Z/Z=[Z(H)-Z(H-max)]/Z(H-max) is about 260% at f=6.5 MHz, and the maximal sensitivity reaches value up to about 0.88% (A/m)(-1) (66.6% Oe(-1)) at f=10.5 MHz. The correlation between the magnetic properties and the GMI effect shows that the excellent soft magnetic properties and proper transverse anisotropy play a decisive role in the occurrence of the GMI effect. (C) 1999 American Institute of Physics. [S0021-8979(99)03518-5].