Critical current density and vortex dynamics in uranium irradiated Co-doped BaFe2As2

We report the effect of defects introduced by heavy-ion irradiation with 2.6 GeV uranium ions at several matching fields in single crystalline Ba(Fe0.925Co0.075)2As2. The suppression rate of Tc at lower matching fields is larger than that at higher matching fields. The critical current density calculated from magnetic hysteresis loop is enhanced up to 4.1 × 106 A/cm2 at 2 K. Clear dips in magnetic hysteresis loops near zero field are observed at high matching fields. Field dependence of normalized relaxation rate is suppressed, and the relationship between the dip and the relaxation rate is discussed.

► Columnar defects are introduced by 2.6 GeV uranium ions in Ba(Fe0.925Co0.075)2As2.
► Jc is enhanced up to 4.1 MA/cm2 at 2 K in the sample with BΦ = 16 T.
► The slope of Tc change at low BΦ is −0.6 K/T and it is suppressed at higher BΦ’s.
► Clear dips in magnetic hysteresis loops near zero field are observed at higher BΦ’s.