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

Abstract

The giant magnetoimpedance effect in composite wires consisting 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 magnetic material.

Torsion annealing influence on the impedance behaviour in amorphous FeSiB and CoSiB wires

“…The off-diagonal f /z component has been enhanced for the reinforced helical anisotropy at the wire surface [12,13]. Fig.…”

Giant magneto-impedance and skin effect in CuBe/CoNiP composite wires

“…It indicates the current will no longer homogeneously distribute in the composite wire. From a theoretical point of view, we simulated the current density distributions of S3 at different frequencies by means of a simultaneous solution of Maxwell equations and Landau-Lifshitz equation [21]. In the calculation, the conductivities of CuBe core and CoNiP magnetic coating are about 5.23 Â 10 7 and 2.46 Â 10 6 (Om) À1 according to the experimental results, respectively.…”

Magnetoimpedance in soft magnetic amorphous and nanostructured wires

“…This shows that the circular permeability decreases due to the development of the helical induced anisotropy. The off-diagonal ζ φz component has been enhanced for the reinforced helical anisotropy at the wire surface [49,50]. Figure 16 shows the case of other Fe 73.5 Si 13.5 B 9 Nb 3 Cu 1 wires, in the aq state, after being partially nanocrystallized (ann), and the last ones after being torsion annealed (t-ann), as they were above defined.…”