Antiferromagnetic Antenna Based on Parametric Resonance Driven by Spatially Non-Uniform Voltage-Controlled Magnetic Anisotropy

Antiferromagnets (AFMs), having no stray fields and terahertz frequency dynamics, are ideal candidates to be employed as material elements in antennas in 5G/6G systems, where compact, efficient antennas working in the radiofrequency are essential. Voltage controlled magnetic anisotropy (VCMA) can provide an energy-efficient electrical method for controlling AFMs thanks to reduced ohmic losses. In addition, VCMA can drive parametric excitation achieving large-amplitude precession of the AFM state achieving greater efficiency than conventional excitation methods. Here, we theoretically study the response of the AFM induced by an incident radiofrequency electromagnetic (EM) wave, modelled as a time-dependent spatially inhomogeneous VCMA drive. We find that it is possible to excite parametrically the AFM at twice the input frequency, with total suppression of the input mode when the incident EM radiation satisfies the standing wave conditions. This shows how this system can be exploited as a receiving antenna in the radiofrequency range with the capability of generating an output signal with twice the input frequency. Therefore, AFM-based antennas could overcome current limitations in traditional antenna designs, offering an in-materio and low-power tool for terahertz communication applications.