Impact of Dzyaloshinskii-Moriya and anisotropic exchange interactions on the spin configurations and excitations in the cubic kagome antiferromagnets Mn₃X and Mn₃AB

We perform a symmetry analysis of the ABC-stacked kagome planes of Mn atoms common to the L1₂ Mn₃X and antiperovskite Mn₃AB alloys. In addition to the single-ion-anisotropy and Kitaev-type anisotropic exchange known to stabilize the 120-degree spin structures in these materials, our analysis results in a staggered Dzyaloshinskii-Moriya interaction and further gamma-type anisotropic exchange between nearest-neighbor spins. The presence of these new terms is shown not to affect the energetics of the 120-degree ground-states which explains their absence in prior minimal magnetic models. We go on to show, however, that the influence of these terms is swithced on when spin-wave excitations are considered, resulting in reduced symmetry and magnon band gaps. We highlight these effects by calculating inelastic neutron scattering cross-sections to illustrate possible experimental routes for probing the existence and relative strengths of these cloaked interactions.