The Effect of 320 MeV Au Irradiation in K-doped Ba-122

We report the effect of 320 MeV Au 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 level of irradiation in agreement with the previous report. Critical current density (Jc) is strongly enhanced by the introduction of defects up to 15 MA/cm2 at 2 K under self- field, which is 10 times larger than the pristine crystal. The field dependence of Jc changes from H-0.5 to H-1, which indicates that columnar defects are effectively introduced in the crystal by the irradiation.