Fe-based ferromagnetic microwires enabled meta-composites

Abstract

The microwave properties of polymer-based glass fiber reinforced composites containing amorphous Fe77Si10B10C3 microwires in parallel and orthogonal arrays and their dependencies on external magnetic field have been investigated. Double-negative-index characteristics are confirmed for both wire arrays through the observed transmission window in the 1–7 GHz frequency band. The microwave interaction within inter-wire range is responsible for a multi-peak feature observed in the absorption spectra of the parallel wire array composite when the wire spacing is below 7 mm. We introduce the term of “effective diameter” associated with the microwire domain structure to remedy the discrepancy between the computed and experimentally observed plasma frequency.

Metacomposite characteristics and their influential factors of polymer composites containing orthogonal ferromagnetic microwire arrays

“…In the case of parallel wire array composite, the displayed multi-peak feature in 6 to 14 GHz frequency band is likely due to the fact that narrowing down wire spacing to a critical value (between 3 and 10 mm in the present study) can induce the 6 long-range dipolar resonance among the wires. 7 On the other hand, it is indicated in Fig. 3(c) that the addition of 10 mm spaced vertical wires to form the orthogonal architecture can dramatically reduce the critical wire spacing to below 10 mm and induce microwave interaction peaks at 7.5…”

“…4(a)), revealing a positive influence of matrix on metacomposite features. In order to achieve a given transmittance level, less wire amount would be needed for a wire 7 composite than a pure wire array. This suggests that the metacomposite features are influenced not only by intrinsic properties and topological arrangement of microwires, but also by the existence of the polymer matrix and the related interface therein.…”

“…6(a). 1,7 More detailed discussion of the effective permittivity of the microwire composites will be done later. Together, intrinsic magnetic properties of microwires and their alignment in the composite indicate the DNG features and explain the identified transmission window.…”

“…Unlike conventional metamaterials, the ultimate properties of such metacomposites are dependent not only on the local properties of microwires but also on their geometrical parameters, which offers more flexibility to manipulate the microstructural configuration to meet different engineering requirements. 7 Fundamentally, it has been confirmed that an array of periodically arranged conductive wires could formulate a left-handed medium in a certain frequency band. 1 It follows that free standing Co-based microwire arrays without any matrix have been proved to exhibit a typical metamaterial behaviour as verified by the transmission window in the microwave band and the flexible tunability towards the external fields.…”

“…Mostly recently, we have demonstrated that by incorporating parallel Fe-based ferromagnetic microwire arrays into polymer matrix, peculiar metacomposite characteristics can be obtained. 7 Furthermore, an orthogonal structure consisting of ferromagnetic microwires and conductive fibers was proposed by Liu et al 11 and a double-negative behaviour was theoretically predicted. Hence, we believe that, owing to the excellent magnetic properties of Fe-based microwires, more salient metamaterial features could be attained by employing orthogonal ferromagnetic microwire arrays alone, which also lead to more simplified fabrication process.…”