Effects of heavy-ion irradiations in K-doped BaFe2As2

•Effects of columnar defects introduced by heavy-ion irradiations in (Ba0.6K0.4)Fe2As2 are investigated.•Tc is only weakly suppressed by heavy-ion irradiation below BΦ = 8 T.•In all cases, the maximum critical current density reach ∼15 MA cm−2, which is ∼7.5% of the depairing current density.•The Jc enhancement in proportion to BΦ1/2 is understood by the half-loop excitation of vortices.

We report the effects of heavy-ion irradiation in (Ba0.6K0.4)Fe2As2 single crystals including its dose dependence. We found that the suppression of Tc is weak up to a certain dose of irradiation. Critical current density (Jc) under self-field is strongly enhanced up to 15 MA cm−2 at 2 K by the introduction of defects through irradiations with different energies and ion species. This upper limit is in agreement with the previous report for that in cuprate superconductors. The dose dependence of Jc follows BΦ1/2, which can be explained by the simple scenario on the interaction between a driven vortex and discontinuous columnar defects.