Superconductivity and critical current density in LaFeAsO 1 − xF x compounds

Abstract

Here, we report our studies on the crystal structures, morphologies, and superconductivity in LaFeAsO 1 − x F x compounds which were fabricated by solid state reaction. The crystal structures were refined using Rietveld refinement. Superconducting properties, such as critical temperature, T c, critical current density, J c, and upper critical field, H c2, were determined using magneto-transport and magnetic measurements over a wide range of temperature below and above T c, and in magnetic fields up to 14 T. A peak effect in the J c versus field is observed at T < 15 K. Upper critical field in the ab and c directions is H ab c2 = 122.8 T and H c c2 = 38.6 T, respectively.