In-plane magnetic field induced double fan spin structure with $\textit{c}$-axis component in metallic kagome antiferromagnet YMn$_{6}$Sn$_{6}$

TL;DR

This study reveals that in YMn$_{6}$Sn$_{6}$, the topological Hall effect under in-plane magnetic fields arises from a novel double fan spin structure with c-axis components, not skyrmions, as shown by neutron diffraction.

Contribution

The paper experimentally identifies a new in-plane field-induced double fan spin structure with c-axis components in YMn$_{6}$Sn$_{6}$, explaining the topological Hall effect without skyrmions.

Findings

Topological Hall effect observed in YMn$_{6}$Sn$_{6}$ under in-plane magnetic field.

Neutron diffraction reveals a double fan spin structure with c-axis components.

The spin structure differs from skyrmion lattice, providing new insights into magnetic topological phenomena.

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 $\textit{c}$-axis components (DFC). Our work provides the experimental basis from which a microscopic theory can be established to understand the observed THE.