Off-stoichiometry effect on orbital order in A-site manganites probed by x-ray absorption spectroscopy

We here report on the occurrence of strong orbital order driven by off-stoichiometry in oxide manganite films. Multiple-electronic-valence Mn ions are possibly substituted into the perovskite atomic A site (namely, A-site manganites). By combining state-of-the-art synchrotron ultrafine spectroscopies, we did provide evidence of a high ferromagnetic metallic state together with a strong orbital order of Mn ions, despite that the kinetic energy of the free charge carriers should prevent long-range orbital order. By varying the total amount of Mn ions at the perovskite A site, a specific orbital order (either in-plane or out-of-plane) can be determined.