Spin structure and dynamics of the topological semimetal Co$_{3}$Sn$_{2-x}$In$_{x}$S$_{2}$

TL;DR

This study investigates the spin dynamics and magnetic structures of Co$_{3}$Sn$_{2-x}$In$_{x}$S$_{2}$, revealing how magnetism influences the anomalous Hall effect through neutron scattering analysis across different compositions.

Contribution

It provides a microscopic understanding of the interplay between magnetism and the anomalous Hall effect in a Weyl semimetal by analyzing spin structures and dynamics as a function of indium doping.

Findings

Magnetic structure evolves from ferromagnetic to canted antiferromagnetic with doping.

Spin gap and stiffness suggest Weyl fermion contribution to AHE.

Noncollinear spins induce Berry curvature affecting transport.

Abstract

The anomalous Hall effect (AHE), typically observed in ferromagnetic (FM) metals with broken time-reversal symmetry, depends on electronic and magnetic properties. In Co$_{3}$Sn$_{2-x}$In$_{x}$S$_{2}$, a giant AHE has been attributed to Berry curvature associated with the FM Weyl semimetal phase, yet recent studies report complicated magnetism. We use neutron scattering to determine the spin dynamics and structures as a function of $x$ and provide a microscopic understanding of the AHE and magnetism interplay. Spin gap and stiffness indicate a contribution from Weyl fermions consistent with the AHE. The magnetic structure evolves from $c$-axis ferromagnetism at $x$ = 0 to a canted antiferromagnetic (AFM) structure with reduced $c$-axis moment and in-plane AFM order at $x$ = 0.12 and further reduced $c$-axis FM moment at $x$ = 0.3. Since noncollinear spins can induce non-zero Berry curvature in real space acting as a fictitious magnetic field, our results revealed another AHE contribution, establishing the impact of magnetism on transport.