Theory of Antiferromagnet-Based Detector of Terahertz Frequency Signals

Ansar Safin,Andrei Slavin,Vasyl Tyberkevych,Andrei Kirilyuk,Sergey Nikitov

doi:10.3390/magnetochemistry8020026

Abstract

We present a theory of a detector of terahertz-frequency signals based on an antiferromagnetic (AFM) crystal. The conversion of a THz-frequency electromagnetic signal into the DC voltage is realized using the inverse spin Hall effect in an antiferromagnet/heavy metal bilayer. An additional bias DC magnetic field can be used to tune the antiferromagnetic resonance frequency. We show that if a uniaxial AFM is used, the detection of linearly polarized signals is possible only for a non-zero DC magnetic field, while circularly polarized signals can be detected in a zero DC magnetic field. In contrast, a detector based on a biaxial AFM can be used without a bias DC magnetic field for the rectification of both linearly and circularly polarized signals. The sensitivity of a proposed AFM detector can be increased by increasing the magnitude of the bias magnetic field, or by by decreasing the thickness of the AFM layer. We believe that the presented results will be useful for the practical development of tunable, sensitive and portable spintronic detectors of THz-frequency signals based of the antiferromagnetic resonance (AFMR).

Highlights

Frequency-selective and tunable detection of terahertz (THz) frequency signals is an operation that is important for many different applications—from medical scanning, to security, to high-speed 6G communication and radio astronomy [1]
Recent experiments on the effect of spin-pumping performed in both uniaxial [14,15,16] and biaxial [17,18] AFMs indicate the possibility of development of THz frequency-detectors based on antiferromagnet/heavy metal (AFM/HM) heterostructures
Magnetochemistry 2022, 8, 26 as well as the polarization of the received THz-frequency electromagnetic signal, on the possibility of resonance detection of such signals using spin pumping in passive spintronic detectors-based AFM/HM bilayers

Summary

Introduction

Frequency-selective and tunable detection of terahertz (THz) frequency signals is an operation that is important for many different applications—from medical scanning, to security, to high-speed 6G communication and radio astronomy [1]. Magnetochemistry 2022, 8, 26 as well as the polarization of the received THz-frequency electromagnetic signal, on the possibility of resonance detection of such signals using spin pumping in passive spintronic detectors-based AFM/HM bilayers. The influence of the signal polarization and the type of the AFM anisotropy on the detection of THz-frequency signals by the AFM/HM spintronic detectors has been further studied theoretically in [11,13]. The conditions necessary for using uniaxial AFMs for the detection of linearly polarized signals have not been studied in detail, so far It is well-known (see, e.g., [6]) that, in the absence of an external bias magnetic field, the AFMR frequencies in AFM crystals are proportional to the square root of the product of the anisotropy fields and the AFM internal exchange field.

Physical Structure

Magnetization Precession Induced by a Polarized THz EM Signal

Rectification of THz-Frequency Electromagnetic Signals

Conclusions