Coulomb correlation in noncollinear antiferromagnetic α-Mn

We discuss the interplay between magnetic and structural degrees of freedom in elemental Mn. The equilibrium volume is shown to be sensitive to magnetic interactions between the Mn atoms. While the standard generalized gradient approximation underestimates the equilibrium volume, a more accurate treatment of the effects of electronic localization and magnetism is found to solve this longstanding problem. Our calculations also reveal the presence of a magnetic phase in strained α-Mn that has been reported previously in experiments. This new phase of strained α-Mn exhibits a noncollinear spin structure with large magnetic moments. Our results are relevant for smart materials such as the shape-memory and magnetocaloric Mn-rich Heusler alloys because elemental Mn and the Mn-rich Heusler alloys present phase diagrams with common features.

Pulkkinen et al., Phys. Rev. B 101, 075115 (2020)