Surface Magnetoimpedance Measurements in Soft-Ferromagnetic Materials

Abstract

We present an investigation of the surface magnetoimpedance (Z s ) in ribbons of the amorphous alloy Co 70.4 Fe 4.6 Si 15 B 10 for a broad range of frequencies (2× 10 3 Hz≤f≤2 × 10 8 Hz) and magnitudes of the ac electrical current (2 mA ≤ I ac ≤ 75 mA). The experimental data are interpreted in terms of a theoretical model valid for any value of the skin depth δ, which is based on a modification of the currently used semi-infinite sample geometry model, in order to account for a broad range of δ, The shape of the Z S versus applied field (H) curve is mainly determined by the variation of δ with H. which can attain several orders of magnitude in the field range of the experiments (-3.2 × 10 3 A/m ≤ H ≤ 3.2 × 10 3 A/m). The results of the model fit very well the Z S versus f data using three adjustable parameters: the domain-wall relaxation time τ (= 250 ns for all values of I ac used in the experiments), the transversal magnetic permeability X T (I ac ) and a resonance linewidth ΔH which depend on the value of H.