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

TL;DR

This paper demonstrates a novel nano-antenna leveraging tripartite phonon-magnon-photon coupling in a multiferroic crystal, achieving radiation efficiency and gain surpassing traditional antenna limits by over two orders of magnitude.

Contribution

It introduces a new nano-antenna design based on tripartite coupling in multiferroic nanostructures, with experimental validation and micro-magnetic simulations.

Findings

Radiation efficiency exceeds traditional limits by over 100 times.

Antenna gain surpasses theoretical bounds for conventional antennas.

Micro-magnetic simulations match experimental results closely.

Abstract

We investigate tripartite coupling between phonons, magnons and photons in a periodic array of elliptical magnetostrictive nanomagnets delineated on a piezoelectric substrate to form a two-dimensional two-phase multiferroic crystal. A surface acoustic wave (phonons) of 5 - 35 GHz frequency launched into the substrate causes the magnetizations of the nanomagnets to precess at the frequency of the wave, giving rise to spin waves (magnons). The spin waves, in turn, radiate electromagnetic waves (photons) into the surrounding space at the surface acoustic wave frequency. Here, the phonons couple into magnons, which then couple into photons. This tripartite phonon-magnon-photon coupling is exploited to implement an extreme sub-wavelength electromagnetic antenna whose measured radiation efficiency and antenna gain exceed the theoretical limits for traditional antennas 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.