Nanoscale spin rectifiers for harvesting ambient radiofrequency energy

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 the performance of state-of-the-art radiofrequency rectifiers is restricted by thermodynamic limits and high-frequency parasitic impedance. 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−1) and high efficiency (7.81%). The performance of our spin rectifier array relies on self-parametric excitation, driven by voltage-controlled magnetic anisotropy. We show that these spin rectifiers can be used to wirelessly power a sensor at a radiofrequency power of −27 dBm. Sensitive spin rectifier devices can be used to create rectennas that harvest ambient radiofrequency signals between –62 and –20 dBm, and can be used to create on-chip co-planar-waveguide-based spin rectifier arrays with large zero-bias sensitivity and high efficiency.