Joint superexchange-Jahn-Teller mechanism for layered antiferromagnetism in LaMnO 3

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.