Abstract
Current–voltage (
I
–
V
) characteristics of MgB
2
bulk sintered superconductor, prepared from the commercially available powder (Alfa-Aesar), have been investigated before and after several
γ
irradiations up to 5000 MR. A minor increase in the normal state resistance of the sample was observed up to 5000 MR without any change in its critical temperature (
T
c
).
I
–
V
characteristics before and after
γ
irradiation with different doses up to 5000 MR were shown and fitted to the expression
V
∝
I
β
(
T
,
B
)
where
β
approaches unity near
T
c
before and after
γ
irradiation. A decrease in the critical currents (
I
c
) with
γ
irradiation up to 1000 MR was observed; after which they start to increase with higher irradiations up to 5000 MR without exceeding the critical currents before irradiation.