Robust half-metallicity and topological properties in square-net potassium manganese chalcogenides

Combining ab initio and model Hamiltonian approaches, we investigate the electronic, magnetic, and topological properties of potassium manganese chalcogenides that host square nets of Mn and chalcogen atoms. Our analysis establishes these compounds to be robust half-metallic ferromagnets. The origin of ferromagnetism in these compounds is found to be based on a kinetic energy-driven double-exchange mechanism, first proposed for ${\mathrm{Sr}}₂{\mathrm{FeMoO}}₆$, a double-perovskite compound. The presence of finite spin-orbit coupling at chalcogen sites triggers nontrivial topology of the chalcogen-derived bands at the conducting channel, dominating the electronic structure close to the Fermi level. This puts the studied compounds in the class of topological half-metals with appreciable values of anomalous Hall conductivity, opening up the application possibility in topological quantum spintronics. Cleavability of these layered compounds makes the situation further promising.