Metamaterial is an artificially tailored media showing unusual electrodynamic properties based on the use of the resonant elements, so-called meta-atoms. At certain frequencies, the effective magnetic permeability and the electrical permittivity both become negative, resulting in e.g. "left-handed" wave propagation and, therefore, a negative index of refraction. The electrical and magnetic meta-atoms are designed as sub-wavelength size micro-resonators that couple primarily to either the electric or the magnetic field of the incoming electromagnetic wave.
The electrical meta-atom can be realized as metalic wire, i.e. electrical dipol. The magnetic meta-atom is usually fulfiled in form of a split-ring resonator. The key point of this work is planar superconducting spiral resonator using as a component of the metameterials. The planar spiral resonators were proposed in order to drastically reduce, in comparison with the split-ring resonators, the resonator size relative to the wavelength. These spiral resonators have multiple resonance modes and have a potential of designing ultra-compact magnetic meta-atoms.