I−V curves and intergranular flux activation energy in the magnetic superconductor RuSr2GdCu2O8

Abstract

A systematic study of I−V characteristic curves for RuSr2RCu2O8 [Ru−(1212)] is presented, with magnetic fields up to 3T and 2K⩽T⩽30K, in the region of the superconducting transition. The activation energy Ea(H,T) for flux line depinning was determined by fitting the nonlinear region of the curves up to the flux flow regime. Ea(H,T) was found to increase linearly on cooling without saturation down to T∕TSC=0.25, while a power-law dependence on the magnetic field was observed up to H=0.1T, where an abrupt reduction in its decreasing rate occurs. The value extrapolated for Ea(0,0)≃50meV, is twice the reported value for YBa2Cu3O7−δ, but the critical current density JC(0,0)≃70A∕cm2 is about one order of magnitude lower. These results are explained as a consequence of the contribution of the magnetization in the grains to the effective field at the intergranular links and to a spin-flop transition of the Ru-sublattice.

Source-reported materials — not catalogue approval

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