Spin Wave Electromagnetic Nano-Antenna Enabled by Tripartite Phonon-Magnon-Photon Coupling

Tripartite coupling between phonons, magnons, and photons in a periodic array of elliptical magnetostrictive nanomagnets delineated on a piezoelectric substrate to form a 2D two-phase multiferroic crystal is investigated. Surface acoustic waves (SAW) (phonons) of 5-35 GHz frequency launched into the substrate cause the magnetizations of the nanomagnets to precess at the frequency of the wave, giving rise to confined spin-wave modes (magnons) within the nanomagnets. The spin waves, in turn, radiate electromagnetic waves (photons) into the surrounding space at the SAW frequency. Here, the phonons couple into magnons, which then couple into photons. This tripartite phonon-magnon-photon coupling is thus exploited to implement an extreme sub-wavelength electromagnetic antenna whose measured radiation efficiency and antenna gain exceed the approximate theoretical limits for traditional antennas of the same dimensions by more than two orders of magnitude at some frequencies. Micro-magnetic simulations are in excellent agreement with experimental observations and provide insight into the spin-wave modes that couple into radiating electromagnetic modes to implement the antenna.

Automated summary

This study investigates the tripartite coupling between phonons, magnons, and photons in a periodic array of elliptical magnetostrictive nanomagnets on a piezoelectric substrate to form a 2D two-phase multiferroic crystal. The phonons launch surface acoustic waves (SAW) that cause the spin-wave modes (magnons) within the nanomagnets to radiate electromagnetic waves (photons). This phonon-magnon-photon coupling is exploited to implement an extreme sub-wavelength electromagnetic antenna with significantly higher radiation efficiency and antenna gain compared to traditional antennas of the same size.