Simulation of light C4+ ion irradiation and its enhancement to the critical current density in BaFe1.9Ni0.1As2 single crystals

In this work, we analyse the influence of C4+ irradiation with ion flounce of 3 x 10(12) up to 2.3 x 10(15) ion cm(-2) on significant enhancement of the critical current density, J(c), in BaFe1.9Ni0.1As2 single crystals. J(c) was increased from 0.61 x 10(5) up to 0.94 x 10(5) A/cm(2) at T = 10 K and H = 0.5 T. BaFe1.9Ni0.1As2 single crystals with and without the C4+-irradiation 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, T-c. It is found that the C4+-irradiation causes little change in Tc, but it can greatly enhance the in-field critical current density by a factor of up to 1.5. Higher dose of C4+ ions, causes further Jc enhancement at T = 10 K. furthermore, flux jumping completely disappeared at T = 2 K after second C4+-irradiation. Our Monte Carlo simulation results show that all the C4+ ions end up in a well defined layer, causing extended defects and vacancies at the layer, but few defects elsewhere on the irradiation paths. Furthermore, the normal state resistivity is enhanced by the light C4+ irradiation, while the upper critical field, H-c2, the irreversibility field, H-irr, and T-c were affected very little.