Analysis of current-density distribution and giant magnetoimpedance effect in composite wires

The current-density distribution and giant magnetoimpedance (GMI) properties are theoretically described for the homogenous ferromagnetic wires and composite wires consisting of an inner conductive core covered by an outer ferromagnetic coating. The numerical simulation shows that the current is distributed much closer to the surface for the Cu/FeCoNi composite wires than for FeCoNi homogenous ferromagnetic wires at the same frequency and with the same geometric size and magnetic structure. When obvious MI effect can be observed, the skin effect has already been strong in its ferromagnetic coating. The skin effect is still an important factor for the GMI effect in composite wires. Above a certain frequency of about 4 MHz, the driving current will flow through the ferromagnetic coating mainly and the electromagnetic interactions become weaker, the MI behavior in the composite wire becomes similar to that in the homogenous ferromagnetic wire.