Magnetic and topological properties of Kagome metal YMn₆Sn₆

The Kagome lattice has historically been known for frustration-driven novel phenomena, such as spin-liquid phases. Recent experiments have indicated that 3D kagome magnets provide a natural platform to study the effect of the interplay between magnetism and electronic topology. For example, Weyl fermions and a non-collinear spin texture are observed in Mn₃Sn, heavy Dirac bands are reported in frustrated ferromagnet Fe₃Sn₂, and flat bands and Dirac cones are realized in antiferromagnetic FeSn. Here we present our recent findings of the complex nature of the magnetism and topological features in the electronic structure of a ternary kagome magnet, YMn₆Sn₆. This compound orders with a commensurate antiferromagnetic helical structure below 340 K, which on cooling shows an incommensurate double helical structure. Both wave vectors are temperature dependent with the difference in q between the two helices gradually decreasing with decreasing temperature but remaining in the ground state. Electronic band structure calculations show the presence of a Dirac point near the Fermi energy, and a linear magnetoresistance is observed at low temperature when a magnetic field is applied along c-axis.