Critical properties of superconducting Ba 1−xK xFe 2As 2

Abstract

Magnetisation and magneto-resistance measurements have been carried out on superconducting Ba 1− x K x Fe 2As 2 samples with x = 0.40 and 0.50. From high field magnetization hysteresis measurements carried out in fields up to 16 T at 4.2 K and 20 K, the critical current density has been evaluated using the Bean critical state model. The J C determined from the high field data is >10 4 A/cm 2 at 4.2 K and 5 T. The superconducting transitions were also measured resistively in increasing applied magnetic fields up to 12 T. From the variation of the T C onset with applied field, d H C2/d T at T C was obtained to be −7.708 T/K and −5.57 T/K in the samples with x = 0.40 and 0.50.