Current distribution and giant magnetoimpedance in composite wires with helical magnetic anisotropy

TL;DR

This paper theoretically investigates the giant magnetoimpedance effect in composite wires with a non-magnetic core and a magnetic shell exhibiting helical anisotropy, analyzing how impedance depends on anisotropy and shell thickness.

Contribution

It provides analytical expressions for impedance in composite wires with helical magnetic anisotropy, revealing optimal conditions for maximum sensitivity and impedance ratio.

Findings

Maximum sensitivity occurs with circular anisotropy.

Optimal shell thickness equals the magnetic skin depth.

Impedance expressions derived for low and high frequencies.

Abstract

The giant magnetoimpedance effect in composite wires consising of a non-magnetic inner core and soft magnetic shell is studied theoretically. It is assumed that the magnetic shell has a helical anisotropy. The current and field distributions in the composite wire are found by means of a simultaneous solution of Maxwell equations and the Landau-Lifshitz equation. The expressions for the diagonal and off-diagonal impedance are obtained for low and high frequencies. The dependences of the impedance on the anisotropy axis angle and the shell thickness are analyzed. Maximum field sensitivity is shown to correspond to the case of the circular anisotropy in the magnetic shell. It is demonstrated that the optimum shell thickness to obtain maximum impedance ratio is equal to the effective skin depth in the mahnetic material.