Soft x-ray resonant scattering study of single-crystal La[Sr.sub.2][Mn.sub.2][O.sub.7]

Soft X-ray resonant scattering studies at the Mn [L.sub.II,III]-and the La [M.sub.IV,V]-edges of single-crystal La[Sr.sub.2][Mn.sub.2][O.sub.7] are reported. At low temperatures, below [T.sub.N] ≅ 160 K, energy scans with a fixed momentum transfer at the 4-type anti-ferromagnetic (0 0 1) reflection around the [M.sub.n] [L.sub.II, III-] edges with incident linear σ and π polarizations show strong resonant enhancements. The splitting of the energy spectra around the Mn [L.sub.II,III]-edges may indicate the presence of a mixed valence state, e.g., [Mn.sup.3+]/[Mn.sup.4+]. The relative intensities of the resonance and the clear shoulder-feature as well as the strong incident σ and π polarization dependences strongly indicate its complex electronic origin. Unexpected enhancement of the charge Bragg (0 0 2) reflection at the La [M.sub.IV, V]-edges with σ polarization has been observed up to 300 K, with an anomaly appearing around the orbital-ordering transition temperature, [T.sub.00] ≅ 220 K, suggesting a strong coupling (competition) between them.