Electronic structure and exchange interaction in the layered perovskite Sr3Mn2O7
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The electronic structure of the Ruddlesden-Popper layered perovskite compound Sr3Mn2O7 is studied from density-functional calculations using the linear muffin-tin orbitals method. An antiferromagnetic, insulating solution is obtained in agreement with the experiments, with a magnetic moment of about 2.52mu(B) 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 (m(z)*/m(x,y)* similar to 10.9 for electrons and similar to4.2 for holes), while for the related compound LaSr2Mn2O7, which is a ferromagnetic metal, we obtain a strong anisot...ropy in the resistivity rho(c)/rho(ab)similar to40 using kinetic transport theory, in qualitative agreement with the experimental value of similar to100.