The field dependence of the critical current density, jc (B), of MgB2 doped with 10 weight % liquid precursor, silicone oil, was measured. The enhanced jc (B) compared to the pure MgB2 was obtained. An observed temperature dependence of the crossover field, Bsb(T), from the single vortex to the small vortex bundle pinning regime shows that δl pinning behavior, i.e., pinning associated with charge-carrier mean free path fluctuations, is dominant for temperature below 20 K.

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