Micromagnetic modeling of Terahertz oscillations in an antiferromagnetic material driven by spin-Hall effect

TL;DR

This paper models THz oscillations in antiferromagnetic thin films driven by the spin-Hall effect, revealing two distinct dynamical modes influenced by Dzyaloshinskii-Moriya interaction strength.

Contribution

It provides a comprehensive micromagnetic simulation study of THz oscillators in AFMs, highlighting the impact of DMI on their dynamical behavior.

Findings

Two dynamical modes depending on DMI strength

Large amplitude uniform precession at low DMI

Ultrafast domain wall motion at high DMI

Abstract

The realization of THz sources is a fundamental aspect for a wide range of applications. Over different approaches, compact THz oscillators can be realized taking advantage of dynamics in antiferromagnetic (AFMs) thin films driven by spin-Hall effect. Here we perform a systematic study of these THz oscillators within a full micromagnetic solver based on the numerical solution of two coupled Landau-Lifshitz-Gilbert-Slonczewski equations, for the case of ultra-thin films, i.e. when the N\'eel temperature of an AFM is substantially reduced. We have found two different dynamical modes depending on the strength of the Dzyaloshinskii-Moriya interaction (DMI). At low DMI, a large amplitude precession is excited where both the magnetizations of the sublattices are in a uniform state and rotate in the same direction. At large enough DMI, the ground state of the AFM becomes non-uniform and the antiferromagnetic dynamics is characterized by ultrafast domain wall motion.