Simulation of light C4+ ion irradiation and its significant enhancement   to the critical current density in BaFe1.9Ni0.1As2 single crystals
  In this work, we report the simulation of C4+ irradiation and its significant effects towards the enhancement of the critical current density in BaFe1.9Ni0.1As2 single crystals. BaFe1.9Ni0.1As2 single crystals with and without the C-implantation were characterized by magneto-transport and magnetic measurements up to 13 T over a wide range of temperatures below and above the superconducting critical temperature, Tc. It is found that the C-implantation causes little change in Tc, but it can greatly enhance the in-field critical current density by a factor of up to 1.5 with enhanced flux jumping at 2 K. Our Monte Carlo simulation results show that all the C ions end up in a well defined layer, causing extended defects and vacancies at the layer, but few defects elsewhere on the implantation paths. This type of defect distribution is distinct from the columnar defects produced by heavy ion implantation. Furthermore, the normal state resistivity is enhanced by the light C4+ irradiation, while the upper critical field, Hc2, the irreversibility field, Hirr, and Tc were affected very little. 
M. Shahbazi, X.L. Wang, M. Ionescu, S. R. Ghorbani, S. X. Dou, K.Y.   Choi, K.K. Chung
cond-mat.supr-con