Design comparison and magnetic control of negative permeability metamaterials

Four types of split ring resonators (SRRs), the so-called single-slit SRRs, two-slit SRRs (TSRRs), double-ring SRRs, and modified SRRs, have been considered and numerically investigated for the comparative analysis in connection with their suitability to the design of tunable metamaterials. It is found that the TSSR configuration on the gigahertz resonance reveals a larger variation in the magnetic resonance frequency through the influences of the SRR size scaling, the slit width and the substrate permittivity. Based on the TSRR structure infiltrated with liquid crystals (LCs) in the sandwich substrate, a tunable magnetic metamaterial was proposed in this study. The main relevant contribution of this paper is to provide a tuning procedure via controlling the director orientation of anisotropic LCs and to show that the TSRR structure can be designed to exhibit negative permeability over a broad frequency interval. The magnetic resonance frequencies could be adjusted in the microwave range of about 7.82 to 8.92 GHz.