Extreme sub-wavelength magneto-elastic electromagnetic antenna implemented with multiferroic nanomagnets

TL;DR

This paper demonstrates an ultra-miniature electromagnetic antenna using multiferroic nanomagnets actuated by surface acoustic waves, achieving radiation efficiency far exceeding traditional limits and enabling significant miniaturization of communication devices.

Contribution

The authors introduce a novel extreme sub-wavelength EM antenna design that surpasses the A/(lambda)^2 efficiency limit using magneto-elastic effects and surface acoustic waves.

Findings

Achieved over 10^5 times efficiency beyond the classical limit.

Implemented an antenna with a wavelength of 2 meters and an emitting area of 10^-8 m^2.

Demonstrated drastic miniaturization potential for communication systems.

Abstract

Antennas typically have emission/radiation efficiencies bounded by A/(lambda)^2 (A < lambda^2) where A is the emitting area and lambda is the wavelength of the emitted wavelength. That makes it challenging to miniaturize antennas to extreme sub-wavelength dimensions. One way to overcome this challenge is to actuate an antenna not at the resonance of the emitted wave, but at the resonance of a different excitation that has a much shorter wavelength at the same frequency. We have actuated an electromagnetic (EM) antenna with a surface acoustic wave (SAW) whose wavelength is about five orders of magnitude smaller than the EM wavelength at the same frequency. This allowed us to implement an extreme sub-wavelength EM antenna, radiating an EM wave of wavelength lambda = 2 m, whose emitting area is ~10^-8 m2 (A/lambda^2 = 2.5 10^-9), and whose measured radiation efficiency exceeded the A/(lambda)^2 limit by over 10^5. The antenna consisted of magnetostrictive nanomagnets deposited on a piezoelectric substrate. A SAW launched in the substrate with an alternating electrical voltage periodically strained the nanomagnets and rotated their magnetizations owing to the Villari effect. The oscillating magnetizations emitted EM waves at the frequency of the SAW. These extreme sub-wavelength antennas, that radiate with efficiencies a few orders of magnitude larger than the A/(lambda)^2 limit, allow drastic miniaturization of communication systems.