Magnetism and superconductivity in GdBa₂Cu₃O_7-x

Abstract

The coexistence of magnetism and superconductivity in the high-Tc compound GdBa2Cu3O7-x (x approximately 0) and the influence of oxygen deficiency on the magnetic properties in a sample with x>0.5 have been studied by measurements of the specific heat and the bulk magnetisation and by 155Gd Mossbauer spectroscopy. The magnetic ordering is found to have a pronounced two-dimensional character. The orientation of the ordered Gd moments parallel to the c axis shows the ordering to be due to an anisotropic superexchange interaction. The effect of oxygen vacancies on the magnetic properties is marginal. No indications for magnetic moments at Cu ions was found.