Connecting Topology and Magnetism



The kagome magnet Co3Sn2S2 has recently attracted a lot of attention as a promising Weyl semimetal candidate. One of the interesting observations has been that the magnitude of the Anomalous Hall Effect is constant with temperature below 90 K and then gradually decreases until the magnetic order disappears at around 170 K.

In our recent muon study, we found that this temperature range, in fact, corresponds to the presence of two competing magnetic orders: At low temperatures, there is a ferromagnetic ground state but an in-plane antiferromagnetic state appears at temperatures above 90 K, eventually attaining a volume fraction of 80% around 170 K, before reaching a non-magnetic state. The behavior of the anomalous Hall conductivity is found to be related to the volume fraction of the ferromagnetic state.

This study is interesting for two reasons. First, it establishes a link between the topological properties, such as Berry curvature and magnetism as well as provides the evidence of tuning the Berry curvature through magnetic phase competition. The second reason is no less exciting – In this study, we combined detailed DFT calculations which obtained the muon stopping site with the local field calculations at the muon site to obtain a qualitative picture and a physical model of the two competing phases. This points to the direction of muSR progressively becoming a more quantitative technique.

Find out more at: Nature Communications 11, 559 (2020)