Magnetic ordering of Gd and Cu in superconducting and nonsuperconductingGdBa2Cu3O7−δ

An investigation of the magnetic properties of superconducting and nonsuperconducting samples of $\mathrm{Gd}{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-\delta }$ has been carried out. The antiferromagnetic transition temperature for the Gd ions in the material is the same for both compounds (2.2 K) although the superconducting compound shows metallic behavior and the nonsuperconducting compound shows semiconducting behavior. This provides direct evidence for the lack of magnetic interactions mediated by conduction electrons in these materials. In the nonsuperconducting material, evidence is obtained for the presence of antiferromagnetic ordering in the Cu sublattice at a temperature of 18 K.