Magneto-impedance in glass-coated CoMnSiB amorphous microwires

A magneto-impedance (MI) effect has been experimentally detected and systematically studied in Co/sub 68.5/Mn/sub 0.5/Si/sub 10/B/sub 15/ glass-coated amorphous microwire 14 /spl mu/m in diameter. The dependence of MI on a dc applied magnetic field (up to 20 Oe) for a range of values of ac current (less than 4 mA and having a frequency between 0.2 and 2.0 MHz) flowing along the microwire has been measured in as-prepared samples, as well as after heat treatments up to 400/spl deg/C. A maximum relative change in MI of around 16% is observed in the optimum conditions, that is, for about 5 Oe dc axial applied field and 3 mA, 2 MHz ac current flowing along the microwire, which finally corresponds to a magnetic field sensitivity of about 0.4 V/Oe. Such modifications are interpreted considering the dependence of the skin-effect on those parameters through the induced changes in the circular permeability. MI in these ferromagnetic wires with micrometric dimension is of technological interest for local detection of magnetic fields.