Swift heavy ion irradiation of MgB2 thin films: a comparison between gold and silver ion irradiations

Abstract

The effect of 200 MeV Au ion irradiation on the temperature and field dependence of the critical currentdensity, Jc, of MgB2 thin films on sapphire substrates is reported. The results have beenpresented in comparison with those obtained after 200 MeV Ag ionirradiation of a similar film. After irradiation, the critical temperatureTc decreased for all samples except for the one with a higher dose of gold ions, where itincreased marginally. This observation was also confirmed from measurementsof magnetization as a function of temperature with a constant applied field of10−2 T. The criticalcurrent density, Jc, was estimated from the widths of magnetization loops using Bean’s critical state model. It has been foundthat Jc increases after irradiation, the enhancement being morepronounced for the Au ion irradiation. The higher enhancement ofJc by Au ion irradiation may be attributed to higher flux-pinning efficiency of theirradiated samples. It has been concluded that, although the flux-line shear (FLS)model satisfactorily explains the silver ion irradiation induced enhancement ofJc, some other mechanisms also seem to play a role in theJc enhancement by gold ion irradiation.