Coexistence of antiferromagnetism and superconductivity in YBa2(Cu1−xFex)3O7 only for x around 0.10

Abstract

$\mathrm{Y}{\mathrm{Ba}}_2{\left({\mathrm{Cu}}_{1-x}{\mathrm{Fe}}_x\right)}_3{\mathrm{O}}_7$ compounds for $0\le x\le 0.30$ show a continuous orthorhombic-tetragonal phase transition at $x\approx 0.05$. Both the diamagnetic onset temperature $T_c$ and the effective iron moment decrease with increasing $x$. Coexistence of antiferromagnetism and superconductivity is observed only for $x=0.10\mathrm{} \mathrm{and} 0.12$ as determined by magnetic-susceptibility measurements. The antiferromagnetic order may result from the Ruderman-Kittel-Kasuya-Yosida interaction.