Magnetic Control of Negative Permeability Metamaterials based on Liquid Crystals

We demonstrate numerically and experimentally a magnetically tunable negative permeability metamaterial consisting of an array of broadside coupled split ring resonators infiltrated with liquid crystals (LCs). We stress by a comparative analysis of the LC influence on the resonant frequency under isotropic and anisotropic conditions, the specificities of the tunability of the electromagnetic properties via the substrate permittivity tensor. Experiments were carried out on the basis of a prototype designed and fabricated for X-band operation and infiltrated with a nematic LC with birefringence Deltan=0.18. Scattering parameters analysis shows a resonant frequency shift of 0.3 GHz obtained by reorienting the layered LC by means of permanent magnets; these results being in good agreement with the anisotropic theoretical approach.