Magnetoresistance, critical current density, and magnetic flux pinning mechanism in nickel doped BaFe2As2 single crystals

The critical current density, Jc, flux pinning behavior and magneto- resistance results of BaFe2-xNixAs2 single crystal have been investigated in fields up to 13 T over a temperature range of 2 to 20 K. The magnetoresistance below the superconducting transition temperature (Tc) shows Arrhenius thermally activated behavior: ρ = ρoexp(-Uo(T,H)/kBT), where Uo is the thermally activated energy. BaFe2-xNixAs2 exhibits high thermally activated flux flow energy with a very weak field dependence. Jc is as high as 2 × 105 A/cm2 for zero magnetic field at 2 K. Jc was found to decrease for B B > 1 T at T  = 2, 5, and 10 K. Flux jumping was also observed in magnetization loops at very low temperature for large sample, which is related to the high Jc in the single crystal. A peak effect was observed at 10 K.