Study of the electronic and magnetic properties as a function of isoelectronic substitution in SmFe1-xRuxAsO0.85F0.15

We have studied the electronic and magnetic properties of SmFe1-xRuxAsO0.85F0.15 (x = 0, 0.05, 0.25, 0.33, 0.5) by high-resolution x-ray absorption and x-ray emission spectroscopy. The local Fe magnetic moment (mu) tends to decrease for a small Ru substitution, but it shows a clear increase with further substitution. It appears that impurity scattering prevails in reducing the mu with small Ru substitution due to an extended Ru d-band. A nanoscale phase separation, that decouples the FeAs layers from the spacer layers, drives the increase of mu at higher Ru substitution. The results provide important information on nanoscale phase separation due to isoelectronic substitution in the active layers of iron-based 1111-superconductors and its effect on the local magnetic properties.