Double stripe ordering in Nd0.5Sr0.5MnO3 determined by resonant soft x-ray scattering

We have studied the low-temperature ordered phase of Nd0.5Sr0.5MnO3 by resonant soft x-ray scattering at the Mn L-2,L-3 edges. Strong resonances were observed at (0 1/2 0) and (0 1/2 0) reflections, which are resolved in momentum space. Azimuthal scans reveal a pi periodicity for both resonances, the minimum intensity being almost zero. The two reflections show a very different energy dependence which extends in the whole energy region of the Mn L-edge. The (0 1/2 0) reflection originates from the anisotropy induced on the d-symmetry projected density of states owing to the local tetragonal distortion at one of the two crystallographic inequivalent Mn sites (the so-called Mn3+ ions in the conventional ionic description). This is similar to the resonance observed at the Mn K edge. We propose that the (0 1/2 0) reflection, which has not its counterpart either on the Mn K-edge resonant scattering or on the magnetic scattering, is originated by anisotropy of the d-symmetry projected density of the so-called Mn4+ sublattice. In this way, the latter reflection could denote a pure orbital ordering in this sublattice.