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

The effect of 200 MeV Au ion irradiation on the temperature and field\ud dependence of the critical current density, Jc, of MgB2 thin films on sapphire\ud substrates is reported. The results have been presented in comparison with\ud those obtained after 200 MeV Ag ion irradiation of a similar film. After\ud irradiation, the critical temperature Tc decreased for all samples except for\ud the one with a higher dose of gold ions, where it increased marginally. This\ud observation was also confirmed from measurements of magnetization as a\ud function of temperature with a constant applied field of 10−2 T. The critical\ud current density, Jc, was estimated from the widths of magnetization loops\ud using Bean’s critical state model. It has been found that Jc increases after\ud irradiation, the enhancement being more pronounced for the Au ion irradiation.\ud The higher enhancement of Jc by Au ion irradiation may be attributed to higher\ud flux-pinning efficiency of the irradiated samples. It has been concluded that,\ud although the flux-line shear (FLS) model satisfactorily explains the silver ion\ud irradiation induced enhancement of Jc, some other mechanisms also seem to\ud play a role in the Jc enhancement by gold ion irradiation