Critical current density and vortex dynamics in pristine and proton-irradiated (Ba, K)Fe2As2

Magnetization and flux creep in pristine and 3 MeV proton-irradiated Ba0.5K0.5Fe2As2 single crystals with a dose of 5.3 x 10(16) cm(-2) are measured. Both the pristine and irradiated samples show sharp superconducting transitions, demonstrating the homogeneity of the sample. The sharp central peak in the pristine sample becomes broader after the irradiation. Commonly observed fish-tail effects in iron-based superconductors disappear in the highly disordered sample after the irradiation. The normalized relaxation rate shows a large field dependence in the pristine sample, while it is weakly field dependent in the proton irradiated sample. The dip structure around zero-field is attributed to either the self-field effect or individual pinning. (c) 2013 Elsevier B.V. All rights reserved.