Critical properties of superconducting Ba_1-xK_xFe₂As₂

Abstract

Magnetisation and magneto-resistance measurements have been carried out on superconducting Ba_1-xK_xFe₂As₂ 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 >10⁴ A/cm² 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, dH_C2/dT 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.