Upper critical field, critical current density and thermally activated flux flow in fluorinedoped CeFeAsO superconductors

Abstract

We report our studies on the crystal structures, morphologies, and superconductivity inCeO1 − xFxFeAs compounds which were fabricated by solid state reaction. The crystal structures were refinedusing Rietveld refinement. Superconducting properties such as critical temperature (Tc), critical currentdensity (Jc), andupper critical field (Hc2) were determined using magneto-transport and magnetic measurement over a wide range of temperature belowTc, and in magneticfields up to 13 T. Jc is 2 × 103 A cm − 2 for thex = 0.1 sample.However, the Jc exhibited a weak dependence on magnetic field forB > 1 T andT = 5 and 10 K. A peakeffect in the Jc as a function of field was observed at 20 K in thex = 0.1 sample. Weestimate Hc2ab of 185 T for CeO0.9F0.1FeAs compound. The broadening of the superconducting transition nearTc with increasing field can be well understood using the thermal activated flux flowmodel. The pinning potential scales as with n = 0.2 for B < 3 T and n = 0.71 for B > 3 T in the x = 0.1 sample.