MAGNETO-IMPEDANCE IN GLASS-COATED COMNSIB AMORPHOUS MICROWIRES

A magneto-impedance (MI) effect has been experimentally detected and s ystematically studied Co68.5Mn6.5Si10B15 glass-coated amorphous microw ire P4 pm in diameter. The dependence of MI on a de applied magnetic h eld (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 micr owire has been measured in as-prepared samples, as weal as after heat treatments up to 400 degrees C. A maximum relative change in MI of aro und 16% is observed in the optimum conditions, that is, for about 5 Oe de axial applied held and 3 mA, 2 MHz ac current flowing along the mi crowire, which finally corresponds to a magnetic held sensitivity of a bout 0.4 V/Oe. Such modifications are interpreted considering the depe ndence of the skin-effect on those parameters through the induced chan ges in the circular permeability. MI in these ferromagnetic wires with micrometric dimension is of technological interest for local detectio n of magnetic fields.