We study the magnetic structure of the ${\left({\text{LaMnO}}_3\right)}_{2n}/{\left({\text{SrMnO}}_3\right)}_n$ superlattices from density-functional calculations. In agreement with the experiments, we find that the magnetism changes with the layer thickness $n$. The reason for the different magnetic structures is shown to be the varying potential barrier across the interface, which controls the leakage of the $\text{Mn-}{e}_g$ electrons from the ${\text{LaMnO}}_3$ side to the ${\text{SrMnO}}_3$ side. This in turn affects the interfacial magnetism via the carrier-mediated Zener double exchange. For the $n=1$ superlattice, the $\text{Mn-}{e}_g$ electrons are more or less spread over the entire lattice so that the magnetic behavior is similar to the equivalent alloy compound ${\text{La}}_{2/3}{\text{Sr}}_{1/3}{\text{MnO}}_3$. For larger $n$, the $e_g$ electron transfer occurs mostly between the two layers adjacent to the interface, thus leaving the magnetism unchanged and bulklike away from the interface region.

• Received 22 October 2008

DOI:https://doi.org/10.1103/PhysRevB.79.054428