Electronic reconstruction at SrMnO$_{3}$-LaMnO$_{3}$ superlattice interfaces

Progress in molecular beam epitaxy made possible the growth of manganese oxide superlattices with the dopant ions arranged in separate regular layers. Little is known about how this ``structural'' doping is reflected into the MnO$_{2}$ planes; for instance what is the plane effective hole concentration. We studied superlattices made of SrMnO$_{3}$ and LaMnO$_{3}$ layers with a doping of x=0.33 using resonant soft x-ray scattering. For scattering momenta at which the non-resonant contribution is suppressed by symmetry, i. e. L=3 in units of the superlattice period, resonant soft x-ray scattering probes the distribution of doped holes, and, in particular, the nature of the interface between the doped and undoped layers. Our measurements at the O K edge show a temperature-dependent hole distribution. This electronic reconstruction which occurs with cooling below T$_{c}$ =220~K is related to the transition of the superlattice to a ferromagnetic state. Resonant scattering spectra at the Mn L edges from spin and orbital distributions have complex shapes providing additional insights into these new materials.