Extremely subwavelength planar magnetic metamaterials

We present highly subwavelength magnetic metamaterials designed for operation at radio frequencies (rf's). A dual-layer design consisting of independent planar spiral elements enables the experimental demonstration of a unit cell size $(a)$ that is ~700 times smaller than the resonant wavelength (λ₀). Simulations indicate that utilization of a conductive via to connect spiral layers permits further optimization and we achieve a unit cell that is λ₀/a~2000. Magnetic metamaterials are characterized by a time domain method which permits determination of the complex magnetic response. Numerical simulations are performed to support experimental data and we find excellent agreement. These designs make metamaterial low-frequency experimental investigations practical and suggest their use for the study of magnetoinductive waves, levitation, and to further enable potential rf applications.