The origin of ferromagnetic interactions in NaMnCl${}_3$: how the response theory reconciles with Goodenough-Kanamori-Anderson rules

Abstract

The on-site Coulomb repulsion $U$ is the key ingredient for describing the magnetic properties of Mott insulators, leading to a popular believe that many limitations of the density-functional theory based methods can be cured by artificially incorporating such on-site interactions for localized electrons in the model form. The layered antiferromagnet NaMnCl${}_3$ reveals quite a different story: while the Coulomb $U$ on the Mn sites controls the strength of antiferromagnetic superexchange interactions, an equally important parameter is the Stoner coupling ${\mathcal{I}}_{\mathrm{Cl}}$ on the ligand sites. The latter is responsible for large ferromagnetic contributions to the interatomic exchange interactions, which in NaMnCl${}_3$ nearly cancel the effect of the superexchange interactions. Although such behavior is anticipated from the phenomenological Goodenough-Kamanori-Anderson rules, the quantitative description of the ligand-related contributions remains disputable. Considering NaMnCl${}_3$ as an example, we discuss how they can be generally taken into account in the linear response theory to regain the dependence of the exchange interactions on ${\mathcal{I}}_{\mathrm{Cl}}$. The problem is complicated by the fact that, for the nearly filled Cl $3p$ shell, the parameters ${\mathcal{I}}_{\mathrm{Cl}}$ are sensitive to the model assumptions.

6 pages, 4 figures

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Cited by in corpus (2)

• Linear response theories for interatomic exchange interactions
• Linear Response Based Theories for Dzyaloshinskii-Moriya Interactions