Mössbauer study of hyperfine interactions in EuFe 2 (As 1−x P x ) 2 and BaFe 2 (As 1−x P x ) 2

Abstract The magnetic properties of the pnictide superconductors with the nominal composition of BaFe 2 (As 0.68 P 0.32 ) 2 and EuFe 2 (As 0.8 P 0.2 ) 2 were studied by 57 Fe Mossbauer spectroscopy. A superconducting transition at 30 K was detected and coexistence of magnetism and superconductivity at low temperatures was observed. The Mossbauer spectra show two iron-atom surroundings, which are attributed to undoped A Fe 2 As 2 and substituted A Fe 2 (As 1− x P x ) 2 , with at least one phosphorus atom in the tetragonal iron environment, ( A = Ba or Eu). These two iron-atom surroundings were attributed to one macroscopic A Fe 2 (As 1− x P x ) 2 phase.