About the ionic state of iron in the Cu sites of the Nd2−xCexCu2−yFeyO4−δ superconductor

Abstract The substitution of a small fraction of Cu atoms by Fe atoms in the copper oxide superconductors has proven to be useful in sensing, with Mossbauer spectroscopy, the local surroundings of the Cu sites of their structures. In this work we report the results of such substitution in the Nd 1.85 Ce 0.15 Cu 2 O 4−δ system. After annealing in argon at high pressure and temperature, a strong quadrupole doublet is observed indicating that the iron atoms have been incorporated into the superconductor structure.