  The interaction between electromagnetic waves and objects is strongly
affected by the shape and material composition of the latter. Artificially
created materials, formed by a subwavelength structuring of their unit cells,
namely metamaterials, can exhibit peculiar responses to electromagnetic
radiation and provide additional powerful degrees of freedom to the scatterer
design. In particular, negative material susceptibilities give rise to strong
resonant interactions with deeply subwavelength particles. While the negative
electrical permittivity of natural noble metals manifests itself in localized
plasmon resonant oscillations, negative magnetic permeability is virtually
non-existent in nature. Here the concept of artificial magnon resonance in
subwavelength objects with effective negative permeability, designed based on
the metamaterial approach, is demonstrated. Strong localized oscillations of
the magnetic fields within an array of split ring resonators, forming a sphere,
hybridize in a collective mode of the structure. As a result, extremely high
scattering cross section, exceeding that of a steel sphere with the same radius
by four orders of magnitude, was demonstrated. Furthermore, the scattering
cross section of subwavelength metamaterial-based sphere was shown to be
comparable to the low frequency (MHz) radar signature of a big military
aircraft. Super scatterers, based on tunable resonances within artificially
created materials, can find use in a broad range of electromagnetic
applications, including wireless communications, radars, RFID, internet of
things hardware and many others.
