Antiferromagnetic Half-skyrmions and Bimerons at room temperature

TL;DR

This paper reports the experimental realization of antiferromagnetic topological textures, such as merons, bimerons, and half-skyrmions, in $ ext{Fe}_2 ext{O}_3$ with potential for low-energy spintronic applications at room temperature.

Contribution

It demonstrates the stabilization and control of antiferromagnetic topological textures in a natural material, using a first-order Kibble-Zurek mechanism, with implications for spintronics.

Findings

Stabilization of merons, bimerons, and half-skyrmions in $ ext{Fe}_2 ext{O}_3$

Textures can be erased and re-generated via magnetic fields and temperature cycling

Characteristic sizes of ~100 nm controlled by material parameters

Abstract

In the quest for post-CMOS technologies, ferromagnetic skyrmions and their anti-particles have shown great promise as topologically protected solitonic information carriers in memory-in-logic or neuromorphic devices. However, the presence of dipolar fields in ferromagnets, restricting the formation of ultra-small topological textures, and the deleterious skyrmion Hall effect when driven by spin torques have thus far inhibited their practical implementations. Antiferromagnetic analogues, which are predicted to demonstrate relativistic dynamics, fast deflection-free motion and size scaling have recently come into intense focus, but their experimental realizations in natural antiferromagnetic systems are yet to emerge. Here, we demonstrate a family of topological antiferromagnetic spin-textures in $\alpha$-Fe$_2$O$_3$ - an earth-abundant oxide insulator - capped with a Pt over-layer. By exploiting a first-order analogue of the Kibble-Zurek mechanism, we stabilize exotic merons-antimerons (half-skyrmions), and bimerons, which can be erased by magnetic fields and re-generated by temperature cycling. These structures have characteristic sizes of the order ~100 nm that can be chemically controlled via precise tuning of the exchange and anisotropy, with pathways to further scaling. Driven by current-based spin torques from the heavy-metal over-layer, some of these AFM textures could emerge as prime candidates for low-energy antiferromagnetic spintronics at room temperature.