Effective pinning potential in Pb-doped Hg-1234 superconductor by ac susceptibility response

From the TEM microanalysis, there is presence of intergrowth structures in our Pb-doped Hg-1234 superconductor. By using the ac susceptibility measurements, the temperature, current density, and magnetic field dependence of the effective pinning potential U(T,H,J) for our Pb-doped Hg-1234 superconductor has been determined. It is found that, the current density dependence of U(T,H,J) obeys the inverse power law of the collective pinning theory. Moreover, as the current density J increases, the effective pinning potential of our Pb-doped specimen is dropped much faster than that of HgBa2Ca2Cu3O8+delta one. It is found that the intergrowth structures in our specimen act as weak pinning centres.