Effects of Fe and Zn substitution upon superconductivity inYBa2Cu4O8

Abstract

We report experimental data about the influence of Fe and Zn substitution on the ${\mathit{T}}_{\mathit{c}}$ of ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_4$ ${\mathrm{O}}_8$. Dopant occupation sites have been found using Mössbauer spectroscopy for Fe and by x-ray diffraction for Zn. The Fe atoms were found to occupy the Cu(1) site predominantly at low concentration, whereas the Zn atoms possibly reside in the Cu(2) site. Both dopants suppress ${\mathit{T}}_{\mathit{c}}$ at the same rate of 23 K/at.% and this phenomenon is completely different from that observed in the ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$ system.