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, $\xi_{ab} > 2850\pm400$ \AA . Our experimental observation shows that the Ru is spin-polarized in Ba(Fe${}_{1-x}$Ru${}_x$)${}_2$As${}_2$ compounds.