The GMI effect attracts growing attention especially owing to the large sensitivity (up to 300%) to the DC magnetic field, when the high- frequency (100 kHz - 20 MHz)electrical current flows along the magnetic conductor. Such GMI effect is mostly observed in magnetic materials with large circular magnetic permeability associated to the vanishing magnetostriction. At such f the GMI effect in magnetic materials with considerable magnetostriction is almost negligible (of the order of few %). Recent progress in tailoring of magnetically soft thin wires enabled to enhance significantly the GMI ratio (up to about 600%) [1] in Co-rich compositions with vanishing magnetostriction, while Fe-rich amorphous microwires with rectangular hysteresis loop exhibit poor initial magnetic permeability and almost do not show GMI effect without special processing.

In this paper we report novel results on the GMI effect at high frequency region (10 MHz -500 MHz) in different compositions of amorphous microwires (Fe-rich, with positive magnetostriction, Co-rich with negative magnetostriction and Co-Fe-rich with vanishing magnetostriction) fabricated by the Taylor-Ulitovski method.

Increasing the frequency the GMI effect significantly increases. For example, the shape of the Z(H) of Co-rich microwires with vanishing magnetostriction shows small hysteresis at low DC magnetic field and non-monotonic dependence with a maximum at certain DC magnetic field, H_m. Such H_m increases with increasing the frequency, f. A remarkable difference in the GMI effect with conventional amorphous wires can be attributed to the different magnetoelastic anisotropy of these wires, which should be ascribed to the differences in the fabrication technique resulting in different frequency dependence of the GMI effect.

1. V. Zhukova, A. Chizhik, A. Zhukov, A. Torcunov, V. Larin and J. Gonzalez, IEEE Trans. Magn. 38, 5, partI, (2002) 3090.

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1. Studies of a structural and magnetic properties of glass-coated nanocrystalline Fe₇₉Hf₇B₁₂Si₂ microwires