Tunable decoupling of coexisting magnetic orders in Co$_{1/3}$TaS$_2$

TL;DR

This paper demonstrates tunable coupling between topological scalar spin chirality and nematic order in Co$_{1/3}$TaS$_2$, revealing a new magnetic multiferroic-like behavior with potential for advanced functionalities.

Contribution

It introduces an all-magnetic analogue of multiferroic behavior in Co$_{1/3}$TaS$_2$, showing how magnetic fields can tune the coupling between coexisting magnetic orders.

Findings

Magnetic field induces strong coupling between scalar spin chirality and nematic order.

Nonreciprocal transport probes global spin chirality.

Topological Hall state shows resistance anomalies due to chiral-nematic coupling.

Abstract

In multiferroics, new physical responses and functionalities emerge when symmetry-distinct order parameters couple. This conventionally occurs when lattice and magnetic degrees of freedom order independently in a material. Here, we report an all-magnetic analogue of multiferroic behavior in the antiferromagnet Co$_{1/3}$TaS$_2$, where topological scalar spin chirality and nematicity coexist on the same spin lattice. While the chiral spin texture generates an anomalous Hall effect (AHE), the nematic order breaks threefold rotational symmetry and dominates longitudinal transport. Crucially, in zero field these symmetry-distinct orders merely coexist yet magnetic fields induce strong coupling between them, thus realizing a new type of multiferroic bebhavior via tuning of the coupling itself instead of direct manipulation of secondary orders. In sub-domain sized devices with achiral geometry, we demonstrate that nonreciprocal transport serves as a symmetry-based probe of the global spin chirality, co-aligned with the strong topological AHE of the system. In Co$_{1/3}$TaS$_2$ the topological Hall state inherits a large resistance anomaly via chiral-nematic coupling, thus our results showcase how hybrid magnetic orders can achieve advanced functionalities by merging symmetry-forbidden material responses.