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 TN=365K 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 ≈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 ρ(300 K)/ρ(2 K) values ≈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 Jin-plane/Jout-of-plane≈10. The predicted spin-wave spectrum is presented.