Nanoscale spin rectifiers for harvesting ambient radiofrequency energy

TL;DR

This paper introduces nanoscale spin rectifiers based on magnetic tunnel junctions capable of efficiently harvesting ambient radiofrequency energy, enabling wireless powering of sensors at very low power levels.

Contribution

The study presents a novel on-chip spin rectifier array with high sensitivity and efficiency, overcoming previous limitations of low a.c.-to-d.c. conversion in spin-based rectifiers.

Findings

Harvests RF signals between -62 and -20 dBm

Achieves high zero-bias sensitivity (~34,500 mV/mW)

Reaches rectification efficiency of 7.81%

Abstract

Radiofrequency harvesting using ambient wireless energy could be used to reduce the carbon footprint of electronic devices. However, ambient radiofrequency energy is weak (less than -20 dBm), and thermodynamic limits and high-frequency parasitic impedance restrict the performance of state-of-the-art radiofrequency rectifiers. Nanoscale spin rectifiers based on magnetic tunnel junctions have recently demonstrated high sensitivity, but suffer from a low a.c.-to-d.c. conversion efficiency (less than 1%). Here, we report a sensitive spin rectifier rectenna that can harvest ambient radiofrequency signals between -62 and -20 dBm. We also develop an on-chip co-planar waveguide-based spin rectifier array with a large zero-bias sensitivity (around 34,500 mV/mW) and high efficiency (7.81%). Self-parametric excitation driven by voltage-controlled magnetic anisotropy is a key mechanism that contributes to the performance of the spin-rectifier array. We show that these spin rectifiers can wirelessly power a sensor at a radiofrequency power of -27 dBm.