In-plane magnetic field induced double fan spin structure with $\text{c}$-axis component in metallic kagome antiferromagnet YMn${}_6$Sn${}_6$

Abstract

The geometrical frustration nature of the kagome lattice makes it a great host to flat electronic band, non-trivial topological properties, and novel magnetisms. Metallic kagome antiferromagnet YMn${}_6$Sn${}_6$ exhibits the topological Hall effect (THE) when an in-plane magnetic field is applied. THE is typically associated with the nanometer-sized non-coplanar spin structure of skyrmions in non-centrosymmetric magnets with large Dzyaloshinskii-Moriya interaction. Here we use single crystal neutron diffraction to determine the field/temperature dependence of the magnetic structure in YMn${}_6$Sn${}_6$. We find that the observed THE cannot arise from a magnetic skyrmion lattice, but instead from an in-plane field-induced double fan spin structure with $\text{c}$-axis components (DFC). Our work provides the experimental basis from which a microscopic theory can be established to understand the observed THE.