||Superconducting critical currents were measured as a function of a perpendicular applied magnetic field in disordered La70Cu30.
It is shown that the pinning force is very sensitive to inhomogeneities already present in the as-quenched samples, although these inhomogeneities have no obvious influence on other superconducting and transport properties. A simple series resistance model is used to explain the magnetic field dependence of the pinning force. A large decrease of the pinning force was obtained for the annealed samples. This behaviour is consistent with the phase separation model that explains the evolution of the superconductive penetration depth. In order to obtain a better characterization of the structural evolution with annealing of the La70Cu30 system, the behaviour of the electrical resistivity, superconducting critical temperature and differential thermal analysis were measured.