National Synchrotron Light Source Symposium

LaMnO3 (LMO) is an orbitally degenerate Mott insulator that exhibits A type antiferromagnetism and orbital order. SrMnO3 (SMO) is a high spin "band" insulator with G type antiferromagnetic order. Recent transport and magnetization measurements of epitaxial LMO-SMO superlattices show that the composite structure is metallic and ferromagnetic with a Curie temperature of 220 K. This suggests that the interface between these two materials is qualitatively different than the bulk. In this talk I will present resonant soft x-ray scattering (RSXS) studies of “8-4” LMO-SMO superlattices at the OK and MnL2,3 edges. The (0,0,3) superlattice reflection, which is forbidden in the nominal structure, is visible near the OK threshold, indicating a real space reconstruction of the low-energy density of states. The (0,0,3) intensity tracks the magnetization data with temperature proving that electronic reconstruction is responsible for ferromagnetism in this system. The MnL3 line shape contains a high energy shoulder indicating split eg levels that grows with decreasing temperature. This shoulder shows no azimuthal dependence. Our results are consistent with a picture in which the orbital degree of freedom is quenched by strain, but the orbital occupancy changes through growth of the depletion region as the mobility rises below Tc. These results suggest a general strategy for using RSXS to study interface effects in oxide devices.