Spin polarization of Ru in superconducting Ba(Fe 0.795 Ru 0.205 ) 2 As 2 studied by x-ray resonant magnetic scattering

We have employed the x-ray resonant magnetic scattering (XRMS) technique at the Ru $L_2$ edge of the Ba(Fe$_{1-x}$Ru$_x$)$_2$As$_2$ ($x = 0.205$) superconductor. We show that pronounced resonance enhancements at the Ru $L_2$ edge are observed at the wave vector which is consistent with the antiferromagnetic propagation vector of the Fe in the undoped BaFe$_2$As$_2$. We also demonstrate that the XRMS signals at the Ru $L_2$ edge follow the magnetic ordering of the Fe with a long correlation length, $\xi_{ab} > 2850\pm400$ A. Our experimental observation shows that the Ru is spin-polarized in Ba(Fe$_{1-x}$Ru$_x$)$_2$As$_2$ compounds.