Impact of Dzyaloshinskii-Moriya and anisotropic exchange interactions on the cubic kagome antiferromagnets Mn$_3$X and Mn$_3$AB

TL;DR

This paper investigates how Dzyaloshinskii-Moriya and anisotropic exchange interactions influence the magnetic excitations in cubic kagome antiferromagnets Mn₃X and Mn₃AB, revealing effects observable via neutron scattering.

Contribution

It identifies and analyzes new staggered Dzyaloshinskii-Moriya and gamma-type anisotropic exchange interactions in these materials, which were previously overlooked in minimal models.

Findings

New interactions do not alter ground-state energies.

These interactions affect spin-wave excitations.

Proposed neutron scattering experiments can detect these interactions.

Abstract

We perform a symmetry analysis of the ABC-stacked kagome planes of Mn atoms common to the $L1_2$ Mn$_3$X and antiperovskite Mn$_3$AB alloys. In addition to the single-ion-anisotropy and Kitaev-type anisotropic exchange known to stabilize 120{\deg} 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{\deg} ground-states which explains their absence in prior minimal magnetic models. We go on to show, however, that their influence becomes apparent when spin-wave excitations are considered. We highlight these effects by calculating inelastic neutron scattering cross-sections to illustrate experimental means of probing the existence and relative strengths of these cloaked interactions.