Orbital and charge ordering in LaSr₂Mn₂O₇ observed by resonant X-ray scattering

Orbital and charge ordering phenomena in bilayered perovskite manganite LaSr₂Mn₂O₇ have been studied by resonant X-ray scattering. Superlattice reflections corresponding to these orderings are observed below 210K. The in-plane and stacking structure of the orbital and charge order is determined from these reflections. The anisotropy of the anomalous atomic scattering factor of Mn³⁺ in the orbital ordered state is observed in the azimuthal angle dependence of the reflections. The anisotropy is attributed to the band dispersion of 4p level due to the layered structure as well as the orbital order. In the course of this study, we have found that charge and orbital orderings collapse simultaneously, maintaining the same correlation lengths with further decreasing temperature.