Structural inhomogeneity effects in resistive superconducting transitions of the magnetic superconductor RuSr2(Gd1.5Ce 0.5)Cu2O10-δ

Abstract

The study of granular effects in resistive superconducting transitions of ceramic ruthenocuprate RuSr2(Gd1.5Ce0.5)Cu 2O10-δprepared by a solid-state reaction method is presented for samples as prepared (ASP) and annealed (12 hours at 845°C) in pure oxygen at 62 atm. The resistive transitions for different measuring currents and applied magnetic fields (up to 8 T) bear evidence of granularity effects determined by inhomogeneous structure of the samples. This is dictated by the polycrystalline structure (with a grain size of a few μm) and oxygen deficiency in grain boundary regions. The resistive curves show clearly the intragranular and intergranular superconducting transitions, the intergranular superconductivity being determined by the Josephson coupling between the grains. This has allowed determination of intragranular (Tc0) and intergranular (Tcg) critical temperatures, which are 34 K and 9.4 K in ASP sample, and 37.3 K and 32.8 K in the 62-atm sample in zero field. The magnetic-field dependences of these characteristic temperatures were studied and discussed. In general, the granularity effects are most pronounced in the ASP sample where great sensitivity to applied current and low magnetic field is found. These effects become, however, much weaker after oxygen annealing. © 2006 IOP Publishing Ltd.