Tunable Ultrafast Dynamics of Antiferromagnetic Vortices in Nanoscale Dots

TL;DR

This paper proposes a tunable, ultrafast antiferromagnetic vortex system in nanoscale dots, demonstrating THz frequency oscillations and controllable vortex interactions for advanced memory and signal processing applications.

Contribution

It introduces a new ultrafast vortex state in antiferromagnetic nanodots with tunable interactions mediated by interfacial Dzyaloshinskii-Moriya interaction, enabling high-frequency device applications.

Findings

Vortex oscillations in the THz regime triggered by electric currents.

Tunable vortex interactions depend on polarity and topological charge.

Potential for high-density memory and ultrafast THz signal devices.

Abstract

Topological vortex textures in magnetic disks have garnered great attention due to their interesting physics and diverse applications. However, up to now, the vortex state has mainly been studied in microsize ferromagnetic disks, which have oscillation frequencies confined to the GHz range. Here, we propose an experimentally feasible ultrasmall and ultrafast vortex state in an antiferromagnetic nanodot surrounded by a heavy metal, which is further harnessed to construct a highly tunable vortex network. We theoretically demonstrate that, interestingly, the interfacial Dzyaloshinskii-Moriya interaction (iDMI) induced by the heavy metal at the boundary of the dot acts as an effective chemical potential for the vortices in the interior. Mimicking the creation of a superfluid vortex by rotation, we show that a magnetic vortex state can be stabilized by this iDMI. Subjecting the system to an electric current can trigger vortex oscillations via spin-transfer torque, which reside in the THz regime and can be further modulated by external magnetic fields. Furthermore, we show that coherent coupling between vortices in different nanodisks can be achieved via an antiferromagnetic link. Remarkably, this interaction depends on the vortex polarity and topological charge and is also exceptionally tunable through the vortex resonance frequency. This opens up the possibility for controllable interconnected networks of antiferromagnetic vortices. Our proposal therefore introduces a new avenue for developing high-density memory, ultrafast logic devices, and THz signal generators, which are ideal for compact integration into microchips.