Hybrid magnetoacoustic metamaterials for ultrasound control

Abstract

We propose a class of metamaterials in which the propagation of acoustic waves is controlled magnetically through magnetoelastic coupling. The metamaterials are formed by a periodic array of thin magnetic layers ("resonators") embedded in a nonmagnetic matrix. Acoustic waves carrying energy through the structure hybridize with the magnetic modes of the resonators ("Fano resonance"). This leads to a rich set of effects, enhanced by Bragg scattering and being most pronounced when the magnetic resonance frequency is close to or lies within acoustic bandgaps. The acoustic reflection from the structure exhibits magnetically induced transparency and Borrmann effect. Our analysis shows that the combined effect of the Bragg scattering and Fano resonance may overcome the magnetic damping, ubiquitous in realistic systems. This paves a route toward the application of such structures in wave computing and signal processing.