Superconductivity in Ru substituted polycrystalline BaFe_2-xRu_xAs₂

Abstract

The occurrence of bulk superconductivity at ~22 K is reported in polycrystalline samples of BaFe_2-xRu_xAs₂ for nominal Ru content in the range of x=0.75-1.125. A systematic suppression of the spin density wave transition temperature (T_SDW) precedes the appearance of superconductivity in the system. A phase diagram is proposed based on the measured T_SDW and superconducting transition temperature (T_C) variations as a function of Ru composition. Band structure calculations, indicate introduction of electron carriers in the system upon Ru substitutiom. The calculated magnetic moment on Fe shows a minimum at x=1.0, suggesting that the suppression of the magnetic moment is associated with the emergence of superconductivity. Results of low temperature and high field Mossbauer measurements are presented. These indicate weakening of magnetic interaction with Ru substitution.