Large anomalous Nernst and inverse spin-Hall effects in epitaxial thin films of kagome semimetal Mn3Ge

Synthesis of crystallographically well-defined thin films of topological materials is important for unraveling their mesoscale quantum properties and for device applications. Mn3Ge, an antiferromagnetic Weyl semimetal with a chiral magnetic structure on a kagome lattice, is expected to have enhanced Berry curvature around Weyl nodes near the Fermi energy, leading to large anomalous Hall/Nernst effects and a large spin-Hall effect. Using magnetron sputtering, we have grown epitaxial thin films of hexagonal D019Mn3Ge that are flat and continuous. Large anomalous Nernst and inverse spin-Hall effects are observed in thermoelectric and spin-pumping devices. The anomalous Nernst signal in our Mn3Ge films is estimated to be 0.1 μV/K and is comparable to that in ferromagnetic Fe, despite Mn3Ge having a weak magnetization of ∼3.5mμB/Mn at room temperature. The spin-mixing conductance is 90.5nm-2 at the Py/Mn3Ge interface, and the spin-Hall angle in Mn3Ge is estimated to be about eight times of that in Pt.