Magnetically polarized Ir dopant atoms in superconducting Ba(Fe1-xIrx)(2)As-2

Abstract

<p>We investigate the magnetic polarization of the Ir 5d dopant states in the pnictide superconductor Ba(Fe1−xIrx)2As2 with x=0.027(2) using Ir L3 edge x-ray resonant magnetic scattering (XRMS). Despite the fact that doping partially suppresses the antiferromagnetic transition, we find that magnetic order survives around the Ir dopant sites. The Ir states are magnetically polarized with commensurate stripe-like antiferromagnetic order and long correlations lengths, ξmag>2800 and >850 Å, in the ab plane and along the c axis, respectively, driven by their interaction with the Fe spins. This Ir magnetic order persists up to the Néel transition of the majority Fe spins at TN=74(2) K. At 5 K we find that magnetic order coexists microscopically with superconductivity in Ba(Fe1−xIrx)2As2. The energy dependence of the XRMS through the Ir L3 edge shows a non-Lorentzian line shape, which we explain in terms of interference between Ir resonant scattering and Fe nonresonant magnetic scattering.</p>