Electronic structure and exchange interaction in the layered perovskite Sr3Mn2O7
The electronic structure of the Ruddlesden-Popper layered perovskite compound Sr3Mn2O7 is studied from density-functional calculations using the linear muffin-tin orbital method. An antiferromagnetic, insulating solution is obtained in agreement with the experiments, with a magnetic moment of about 2.52μB for each Mn atom. The magnetic interactions between the Mn atoms, both within the bilayer and between the bilayers, are shown to arise from superexchange. The intrabilayer interaction involves the three-site Mn-O-Mn superexchange much like the case of the well-known CaMnO3, while the interbilayer exchange, mediated via the longer Mn-O-O-Mn superexchange path, is considerably weaker. Consistent with the layered nature of the compound, we find a strong out-of-plane to in-plane band-mass anisotropy for Sr3Mn2O7(mz*/mx,y*∼10.9 for electrons and ∼4.2 for holes), while for the related compound LaSr3Mn2O7, which is a ferromagnetic metal, we obtain a strong anisotropy in the resistivity ρc/ρab∼40 using kinetic transport theory, in qualitative argument with the experimental value of ∼100.
Phys. Rev. B 65, 094402 (2002)