Diamagnetic properties of YBa2Cu3O7 presintered powders: Critical current densities and a.c. losses

The intrinsic diamagnetic response of YBa2Cu3O7 presintered powders obtained by the citrate pyrolysis method has been studied. The techniques applied were: a.c. susceptibility at zero d.c. field, low field d.c. susceptibility, isothermal magnetization and a.c. susceptibility at varying bias fields up to 5 T. To investigate intragrain links, powders of known sizes were used directly, dispersed in oil and finally in the sintered form. Intragrain inductive critical currents and critical field values are derived. Finally, the experimental results are discussed within the framework of weak link models and flux pinning effects.