Influence of geometry on the giant magnetoimpedance of high-aspect ratio amorphous magnetic ribbons

Abstract

We study the influence of ribbon geometry on the giant magnetoimpedance behaviour of both low-and high-aspect ratio (length (l) /width (w) = 2 to 150) ribbons made from commercially available amorphous magnetic materials. Our results indicate that the GMI with geometry is due to the combination of edge effects (due to damage created by the ribbon cutting process) and global shape anisotropy. In highaspect ratio ribbons (length (l) /width (w) 20) we find that the GMI decreases with width, which we suggest is due to the cutting process creating induced stresses that suppresses the transverse susceptibility at the edge of the material. In lower aspect ratio ribbons (length (l) /width (w) 20), shape anisotropy results in a relatively rapid increase in GMI with increasing length. We conclude that, with suitable optimisation, high-aspect ratio ribbons prepared from commercially available materials are suitable for use as macro-scale sensors that detect small magnetic fields/strains over a large sensing area.

Comparative study of the giant stress impedance behavior of commercial amorphous ribbons for strain sensing applications

“…1(a)]. 25 Of the three samples, the Co-rich sample exhibited the highest susceptibility when compared to the other two ribbon samples. Figure 1 In this study, two sets of ribbons composed of the three materials with common cross sections of 10 mm × 25 μm were prepared by mechanically cutting the foils.…”

“…The sample lengths batch 2 samples were chosen to give the ribbons an aspect ratio (l/w) of 20 where it was expected that GMI/GSI ratios would be maximized. 25 The shorter length of the batch 1 samples was chosen to allow uniform magnetic fields to be applied to them using a Helmholtz coil.…”

“…However, as we showed in a previous study, these effects are relatively minor and are not expected to substantially affect our measurements. 25 GMI measurements under induced stress/strain were performed by measuring the samples' impedance spectra while sweeping the applied field between −150 and +150 Oe and applying constant longitudinal stresses of either 0 or 40 MPa. At both stresses, the ribbons' GMI ratios were then calculated using the expression…”

“…In Ref. 25, we performed the basic characterization of the structural properties of all three materials to confirm the material properties quoted by the supplier. X-ray diffraction (XRD) measurements with Cu Kα radiation affirmed the amorphous crystal structure of all three materials with the single broad peak being observed at 2θ ∼ 45°.…”

“…Recently, we reported on the GMI behavior of three commercialized amorphous ribbons with differing magnetic properties, including the saturation magnetostriction coefficient, λ s . 25 It is widely agreed that λ s determines the magnitude of the GMI response of a material, with lower λ s coefficients resulting in higher GMI ratios. This is because materials with near-zero (or negative) λ s coefficients have higher transverse permeabilities.…”