Superconductivity in a new iron pnictide oxide(Fe2As2)(Sr4(Mg, Ti)2O6)

Abstract

We have discovered a new iron pnictide oxide superconductor(Fe2As2)(Sr4(Mg, Ti)2O6). This material isisostructural with (Fe2As2)(Sr4M2O6) (M = Sc, Cr, V),which were found in previous studies. The structure of this compound is tetragonal with a space group ofP4/nmm andconsists of the anti-fluorite type FeAs layer and perovskite-type block layer. The lattice constants area = 3.935 Å andc = 15.952 Å for(Fe2As2)(Sr4MgTiO6). Bulk superconductivitywith a Tc(onset) of ∼ 26 K was observed for a partially Co-substituted sample. Moreover, Co-free and Ti-rich samples exhibitedhigher Tc(onset)s above 35 K, which were further enhanced by applying high pressures up to ∼ 43 K.