The field dependence of the resistivity and the critical current density, Jc(B), ofMgB2 doped with10wt% wet and dry succinic acid have been investigated by magnetic measurements.The dry succinic acid significantly enhanced the upper critical field, the irreversibility field, and the Jc(B) compared to the wet succinic acid doped MgB2 and the pure MgB2. The field dependence of Jc(B) was analyzed within the collective pinning model. The observed temperature dependence of the crossover field, Bsb(T), from the single vortex to the small vortex bundle pinning regime shows that flux pinning a rising from variation in the critical temperature, δTc, is the dominant mechanism for the wet sample over the whole studied temperature range, while there is a competition between δTc pinning and the pinning from variation in the mean free path, δl, for the dry sample.

Keywords