Magnetic Order and Strain in Hexagonal Manganese Pnictide CaMn₂Bi₂

The manganese pnictide CaMn₂Bi₂, with Mn atoms arranged in a puckered honeycomb structure, shows narrow-gap antiferromagnetism, and it is currently a promising candidate for studying complex electronic and magnetic phenomena, such as magnetotransport effects and potential spin spirals under high pressure. In this paper, we perform a detailed research of the magnetic properties of CaMn₂Bi₂ using density functional theory (DFT) combined with the Hubbard U correction and spin-orbit coupling, which accurately describe the magnetic interactions. Our results obtained for a large number of magnetic configurations are accurately captured by a modified Heisenberg model that includes on-site magnetization terms required to describe magnetic energy excitations. We further study the role of the spin-orbit coupling, and find that the magnetic anisotropy of CaMn₂Bi₂ shows an easy plane, with the preferred magnetization direction exchanged between axes in the plane by applying small strain values. This strain-tunable magnetization, driven by the interplay between spin-orbit interactions and lattice distortions, highlights the potential for controlling magnetic states in Mn-pnictides for future applications in spintronic and magnetoelectric devices.