Electronic, magnetic, and thermodynamic properties of the kagome layer compound FeSn

Single crystals of the single kagome layer compound FeSn are investigated using x-ray and neutron scattering, magnetic susceptibility and magnetization, heat capacity, resistivity, Hall, Seebeck, thermal expansion, thermal conductivity measurements, and density functional theory (DFT). FeSn is a planar antiferromagnet below ${T}_{\mathrm{N}}=365\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ and exhibits ferromagnetic magnetic order within each kagome layer. The in-plane magnetic susceptibility is sensitive to synthesis conditions. Resistivity, Hall and Seebeck results indicate multiple bands near the Fermi energy. The resistivity of FeSn is \ensuremath{\approx}3 times lower for current along the stacking direction than in the plane, suggesting that transport and the bulk electronic structure of FeSn is not quasi-two-dimensional (2D). FeSn is an excellent metal with \ensuremath{\rho}(300 K)/\ensuremath{\rho}(2 K) values \ensuremath{\approx}100 in both directions. While the ordered state is antiferromagnetic, high temperature susceptibility measurements indicate a ferromagnetic Curie-Weiss temperature of 173 K, reflecting the strong in-plane ferromagnetic interactions. DFT calculations show a 3D electronic structure with the Dirac nodal lines along the K-H directions in the magnetic Brillouin zone about 0.3 eV below the Fermi energy, with the Dirac dispersions at the $K$ points gapped by spin-orbit coupling except at the $H$ point. The magnetism, however, is highly 2D with ${J}_{\mathrm{in}\text{\ensuremath{-}}\mathrm{plane}}/{J}_{\mathrm{out}\text{\ensuremath{-}}\mathrm{of}\text{\ensuremath{-}}\mathrm{plane}}\ensuremath{\approx}10$. The predicted spin-wave spectrum is presented.