Dynamic electromagnetic processes in micro-wires inferred from GMI-characteristics

The penetration depth of the skin-effect has been calculated for a specimen in the form of a piece of amorphous glass-coated magnetic micro-wire of the “non-magnetostrictive” composition Co67Fe3.85Ni1.45Mo1.7Si14.5B11.5 displaying large 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 the penetration depth with the applied DC-axial field and frequencies of the AC-current, flowing along the wire, is presented. The so-called Cole–Cole diagrams were also plotted for the same specimen. These diagrams, representing the measured impedance plotted in the complex plane, were obtained for axial DC-magnetic field of selected intensities and circular AC-field generated by an AC-current of various frequencies (1–30 MHz) flowing along the wire specimen. Analysis of the diagrams enabled one to characterize magnetization processes within the wire specimen and also to estimate the median relaxation time of these processes as well as a relative measure of the distribution of relaxation times.