Simulation of Light C<SUP>4+</SUP> Ion Irradiation and Its Enhancement to the Critical Current Density in BaFe<SUB>1.9</SUB>Ni<SUB>0.1</SUB>As<SUB>2</SUB> Single Crystals

Abstract

In this work, we analyse the influence of C4+ irradiation with ion flounce of 3 × 1012 up to 2.3 × 1015 ion·cm−2 on significant enhancement of the critical current density, Jc , in BaFe1.9Ni0.1As2 single crystals. Jc was increased from 0.61 × 105 up to 0.94 × 105 A/cm2 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, Tc . 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 Tc were affected very little.