Superconducting glass-phase diagram for ceramic YBa2Cu 3O7-δ

AC complex magnetic susceptibility of ceramic YBa2Cu3O 7-δ was measured close to the superconducting transition temperature, as a function of the amplitude of the alternating magnetic field and of a superimposed dc field. From the maxima of the imaginary part of susceptibility, the universal scaling of the dc field and the temperature dependence of the intergrain Josephson current were obtained, together with the critical fields : H0, for trapping the flux by the junctions, and H J for the occurrence of bulk superconductivity. The results suggest that these materials have spin-glass-like properties, and are qualitatively consistent with the predictions of models of disordered superconductors.