Possible coexistence of SDW state with superconductivity in Ir doped SmOFeAs

The structure and magnetic phase diagram of the newly discovered Ir-doped SmOFeAs superconductor have been investigated by using a spin generalized gradient approximation SGGA + U method. It was found that iridium doping strengthened interlayer coupling between the [FeAs] and [SmO] layers as well as the delocalized electronic distribution of Fe orbitals. The parent compound SmOFeAs showed a metal–insulator transition with a Mott gap of 1.13 eV when considering an on-site energy of 4.0 eV on Fe 3 d shells. By introducing electrons from iridium, the SmOFe1−xIrxAs system was led to a change from the antiferromagnetic state of Fe-spins with stripe-type into a nonmagnetic state with its superconductivity coexisting with the SDW state.