Electronic structure of the layered manganiteLaSr2Mn2O7

Ab initio electronic structure calculations, based on density-functional theory within the generalized gradient approximation, on ${\mathrm{LaSr}}_2{\mathrm{Mn}}_2{\mathrm{O}}_7$ are reported. The bulk electronic structure shows a gap in the minority-spin channel, while the Fermi energy lies at the bottom of the minority conduction band. At the surface of ${\mathrm{LaSr}}_2{\mathrm{Mn}}_2{\mathrm{O}}_7,$ the magnetic moment per formula unit and the spin polarization at the Fermi energy are lowered with respect to the bulk values.