Electrically Tunable Detector of THz-Frequency Signals Based on an Antiferromagnet

Abstract

The development of small and simple room-temperature devices capable of generating and/or receiving resonant signals in a "THz-gap" still stands a significant challenge. However antiferromagnetic spintronics promises to be the right direction for the research and development of THz technology.Recently [1], [2], it has been theoretically proposed to use active AFM generators for the detection of external THz-frequency signals via the mechanism of injection-locking of such a signal to the oscillations generated by a DC-current-driven AFM/HM THz generator.An alternative way to develop quasi-passive AFM/HM-based detectors [3] is to use the fact that resonance eigenfrequencies of the AFM dynamic modes (standing AFMR modes) lie in the THz frequency range. It has been shown theoretically in [3], that a dielectric AFM having bi-axial anisotropy, such as NiO, can be used for the resonance quadratic rectification of a linearly-polarized AC spin current of THz-frequency, and could have a sensitivity in the range of 102-103 V/W.In this work [4], we propose the concept of an electrically tunable resonance detector of THz-frequency signals based on an antiferromagnetic/heavy metal bilayer. The conversion of a THz-frequency input signal into DC voltage is done using the inverse spin Hall effect in a bilayer. An additional bias DC current in the HM layer can be used to vary the effective anisotropy of the AFM, and, therefore, to tune the AFMR frequency. The proposed hetero-structure works as a resonance-type quadratic detector which can be tuned by the bias current in the range of at least 10% of the AFMR frequency.In addition, we discuss experimental results obtained during spin-pumping experiments with antiferromagnetic/heavy metal bilayer (NiO/Pt). The results were obtained in the HFML-FELIX laboratory where we have access to intense THz radiation free-electron laser source as well as high DC magnetic fields up to 38T. **