Critical currents and pinning forces in Nd2−xCexCuO4− thin films

Critical current density, Jc, and flux-pinning force density, Fp, have been investigated at different temperatures in electron-doped Nd2−xCexCuO4− thin films for magnetic fields, H, applied parallel to the c axis. The reduced pinning force density fFp /Fp max shows a clear scaling behavior when H is normalized to the irreversibility field H, indicating the presence of the same pinning mechanism in the investigated temperature range. Moreover the maximum of Fp as function of the field at each temperature depends linearly on H. The experimental data, interpreted using a modified Anderson-Kim description of the flux-creep theory, imply a magnetic field dependence of the activation energy UHH− with =0.8. This value indicates that in Nd2−xCexCuO4− a quasi-two-dimensional vortex system is present, intermediate between Bi-based and Y-based hole-doped compounds.