Dependencies of inter- and intragrain superconductive transitions in polycrystalline RuSr2GdCu2O8 superconductor on field and frequency

Measurements of the complex ac susceptibility components were employed to extract inter- and intragrain superconductive transition temperatures as well as the average transition temperature of RuSr2GdCu2O8 polycrystalline superconductor. The intra- and intergranular components of the granular susceptibility components were also estimated. It was found that both the intra- and intergranular transition temperatures increase by increasing field frequencies and decrease by increasing the field amplitudes. This might be an indication that the grains of RuSr2GdCu2O8 behave differently from a homogeneous bulk superconductor. The nature of d(X)'/dT curves indicated the presence of a superconducting transition between grains, coupled by weak links with a distribution of critical temperatures, and the superconducting transition within the grains. The two transitions observed are linked to the typical intra- and intergrain transitions of a granular superconductor. The weak coupling between grains might be modeled in terms of Josephson-junction arrays. (C) 2007 Elsevier Masson SAS. All rights reserved.