Superconductivity and critical current density in LaFeAsO1-xFx compounds

Here, we report our studies on the crystal structures, morphologies, and superconductivity in LaFeAsO1 − xFx compounds which were fabricated by solid state reaction. The crystal structures were refined using Rietveld refinement. Superconducting properties, such as critical temperature, Tc, critical current density, Jc, and upper critical field, Hc2, were determined using magneto-transport and magnetic measurements over a wide range of temperature below and above Tc, and in magnetic fields up to 14 T. A peak effect in the Jc versus field is observed at T < 15 K. Upper critical field in the ab and c directions is Habc2 = 122.8 T and Hcc2 = 38.6 T, respectively.