Tunable negative permittivity in nano-carbon coated magnetic microwire polymer metacomposites

While polymer-based metacomposites with embedded ferromagnetic wires have demonstrated metamaterial wave phenomena with potential applications, fine control over the electromagnetic response remains challenging. Our contribution here involves coupling carbon nanotubes (CNT) and graphene oxide (GO) with the wire via electrodeposition and tailoring the dielectric function of the resulting metacomposite by controlling the thickness and morphology of the CNT and degree of thermal reduction in the GO. As the CNT coating thickness is increased, a conversion of dielectric dispersion from Lorentz resonance to Drude plasma oscillation occurs, which is ascribed to the degree of inter-connection between the CNT networks in the coating. Also, the gradual restoration of sp(2) domains and thus expansion of the delocalized pi-electron network upon GO thermal reduction are responsible for such conversion in the GO-coated wires. Apart from the regulation of negative permittivity mechanism, the nano-carbon coatings also allow control over the dielectric parameters, including negative permittivity magnitude, plasma frequency and scattering rates determined by interfacial conditions, defects and roughness of the hybrid fibers. These outcomes offer an alternative way to obtain tailorable negative permittivity in the magnetic wire metacomposites and integrate the design philosophy of multiscale composites to that of metacomposites.