Skin-effect and circumferential permeability in micro-wires utilized in GMI-sensors

The penetration depth of the skin-effect and circumferential permeability have been calculated for a magnetic micro-wire of the nominal composition Co 67Fe 3.85Ni 1.45Mo 1.7Si 14.5B 11.5 displaying large giant magnetoimpedance (GMI) effect. For these calculations a simple model was applied in which a rough assumption was made that the changes of the real component of the impedance are due only to changes in the effective cross-section of the wire for the AC-current. The evolution of both, the penetration depth and circumferential permeability, is presented as a function of the applied DC-axial field at various frequencies of the AC-current, flowing along the wire. These quantities are calculated using the experimental data of the real component of the micro-wire impedance. A comparison of the experimental data obtained for the imaginary component of the impedance with those calculated by the model, shows that the latter gives only a qualitative agreement with the measured dependencies.