Scaling of the magnetic response and field dependence for the characteristic pinning energy in (Y, Nd)Ba2Cu3O7-delta superconductors

Magnetic hysteresis loops for the superconductor (Y, Nd)Ba2Cu3O7-delta have been measured using a SQUID and a vibrating sample magnetometer. The field dependence of the current density and volume pinning force showed well dev eloped maxims and their temperature-dependent characteristics were used to construct different scaling types. The measurement of magnetic hysteresis l oops at different sweep rates enabled the field dependence of the character istic pinning energy to be determined. In all cases a remarkable consistenc y with the Perkins et al (1996 Phys. Rev. B 54 12 551) model was found, whi le the field dependence of the characteristic pinning energy appeared to be inconsistent with the collective pinning theory predication.