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