Synthesis and superconductivity of Fe0.5Cu0.5BaSrRCu2O7+δ superconductors synthesized by high pressure

In this paper, the structure, oxygen content, superconductivity and magnetic properties of Fe0.5Cu0.5BaSrRCu2O7+δ superconductors (R represents rare-earth elements) synthesized by high pressure have been studied. Results indicate that all the AM- (prepared in air under ambient pressure) and the HP- (synthesized by high pressure) samples have tetragonal structure and the HP-samples have smaller lattice parameter c, unit-cell volume and more oxygen content than the AM-samples. None of the AM-samples is superconducting while superconductivity in some HP-samples was found. The HP-samples with larger rare-earth ion have lower Tc. An obvious antiferromagnetic transition has been observed in the M-T curve of Tm-based HP-sample.