An Unconventional Ultra-Sub-Wavelength Receiving Nano-Antenna Activated by ac Spin Pumping and the ac Inverse Spin Hall Effect

TL;DR

This paper introduces an ultra-sub-wavelength nano-antenna activated by ac spin pumping and the inverse spin Hall effect, demonstrating unexpectedly high gain at GHz frequencies despite its tiny size.

Contribution

It presents a novel nano-antenna design that surpasses conventional size and gain limitations using spintronic effects at microwave frequencies.

Findings

Achieved a receiving gain at 2.4 GHz over 4000 times the theoretical limit for its size.

Demonstrated operation at Bluetooth and Wi-Fi frequencies with a tiny antenna area.

Measured a gain of approximately -9 dB at 2.4 GHz.

Abstract

We report an extreme sub-wavelength unconventional receiving antenna. It consists of an array of nanomagnets connected to heavy metal nanostrips. Incident electromagnetic (EM) radiation generates intrinsic and extrinsic spin waves in the nanomagnets, which pump spin into the heavy metal nanostrips at their own frequencies giving rise to a polychromatic alternating voltage across the latter owing to the ac inverse spin Hall effect. This implements a receiving nano-antenna. We demonstrate its operation at two different EM wave frequencies of 1.5 GHz and 2.4 GHz - the latter being the Bluetooth and Wi-Fi frequency. We measure the receiving gain at 2.4 GHz to be approximately -9 db. The free space radiated wavelength "lambda" at 2.4 GHz is 12.5 cm while the antenna area A is merely 160 micron^2, making the ratio A/lambda^2 = 0.97x10^-8. This antenna's receiving gain should be very poor because of the tiny size. Yet the measured gain is more than 4000 times larger than the theoretical limit for a conventional antenna of this size at this wavelength because of the unconventional operating principle.