We propose a mechanism for A-type antiferromagnetism in orthorombic LaMnO_3,
compatible with the large Jahn-Teller splitting inferred from structural data.
Orbital ordering resulting from Jahn-Teller distortions effectively leads to
A-type ordering (antiferromagnetic in the c axis and ferromagnetic in the ab
plane) provided the in-plane distorsion Q_2 is large enough, a condition
generally fulfilled in existing data.Comment: 4 pages Late
