Joint superexchange–Jahn-Teller mechanism for layered antiferromagnetism inLaMnO3

We propose a mechanism for $A$-type antiferromagnetism in orthorhombic ${\mathrm{LaMnO}}_3$, compatible with the large Jahn-Teller splitting inferred from structural data. Orbital ordering resulting from Jahn-Teller distortions effectively leads to layered ordering (antiferromagnetic in the $c$ axis and ferromagnetic in the $\mathrm{ab}$ plane) provided the in-plane distortion $Q_2$ is large enough, a condition generally fulfilled in existing data.