Weyl nodes and magnetostructural instability in antiperovskite Mn₃ZnC

The room temperature ferromagnetic phase of the cubic antiperovskite Mn₃ZnC is suggested from first-principles calculation to be a nodal line Weyl semimetal. Features in the electronic structure that are the hallmark of a nodal line Weyl state - a large density of linear band crossings near the Fermi level - can also be interpreted as signatures of a structural and/or magnetic instability. Indeed, it is known that Mn₃ZnC undergoes transitions upon cooling from a paramagnetic to a cubic ferromagnetic state under ambient conditions and then further into a noncollinear ferrimagnetic tetragonal phase at a temperature between 250 K and 200 K. The existence of Weyl nodes and their destruction via structural and magnetic ordering are likely to be relevant to a range of magnetostructurally coupled materials.