Chiral properties of the zero-field spiral state and field-induced magnetic phases of the itinerant kagome metal YMn$_6$Sn$_6$

TL;DR

This study uncovers complex magnetic phases and chiral properties in YMn$_6$Sn$_6$, revealing intrinsic incommensurate structures and topologically non-trivial features linked to the topological Hall effect.

Contribution

The paper provides the first detailed magnetic structure analysis of two unknown commensurate phases and demonstrates the intrinsic nature of incommensurate magnetic structures in YMn$_6$Sn$_6$.

Findings

Identification of two previously unknown commensurate phases.

Observation of intrinsic incommensurate magnetic structures.

Detection of preferential chirality and topological Hall effect in the zero-field spiral phase.

Abstract

Applying a magnetic field in the hexagonal plane of YMn$_6$Sn$_6$ leads to a complex magnetic phase diagram of commensurate and incommensurate phases, one of which coexists with the topological Hall effect (THE) generated by a unique fluctuation-driven mechanism. Using unpolarized neutron diffraction, we report on the solved magnetic structure for two previously identified, but unknown, commensurate phases. These include a low-temperature, high-field fan-like phase and a room-temperature, low-field canted antiferromagnetic phase. An intermediate incommensurate phase between the fan-like and forced ferromagnetic phases is also identified as the last known phase of the in-plane field-temperature diagram. Additional characterization using synchrotron powder diffraction reveals extremely high-quality, single-phase crystals, which suggests that the presence of two incommensurate magnetic structures throughout much of the phase diagram is an intrinsic property of the system. Interestingly, polarized neutron diffraction shows that the centrosymmetric system hosts preferential chirality in the zero-field double-flat-spiral phase, which, along with the THE, is a topologically non-trivial characteristic.