Microscopic Eu–Mn spin-coupling mechanism

Establish the microscopic mechanism by which the Eu and Mn spins in EuMnSb₂ are coupled and thereby produce the observed canted Eu magnetic structure.

Background

The mean-field description represents the Eu–Mn interaction through phenomenological staggered fields, including a transverse component required to reproduce the Eu-spin canting. Possible microscopic sources include antisymmetric exchange, particularly Dzyaloshinskii–Moriya interactions permitted by the absence of inversion symmetry along relevant Eu–Mn exchange paths, and dipolar interactions. However, the quantitative microscopic mechanism and the corresponding exchange pathways have not yet been established.

References

Several questions therefore remain open: (1) Why does such a large magnetic domain imbalance occur, as evidenced from the non-zero off-diagonal elements of $P_{ij}$ for the Bragg peaks (210) and (220)? (2) What is the origin of the signal denoted $H_{\textrm{c}2}$ observed in the high-field magnetization for $H\parallel c$? Is it related to the flop-like transition predicted by the model for $H \parallel a$? (3) What is the microscopic mechanism that couples the Eu and Mn spins and drives the canted structure?

— Resolving the Magnetic Ground State and Field-Induced Transitions in Magnetic Dirac Semimetal Candidate EuMnSb$_2$  (2608.16724 - Chiu et al., 17 Aug 2026) in Section 6, Conclusion and Outlook