Field dependence of the magnetization of melt textured and ceramic Y-Ba-Cu-O

We report on the field dependence of the zero-field-cooled magnetization of cylindrical melt textured and ceramic samples, both having similar packing factors, ≈80%. We define an effective demagnetizing factor, N_eff, which depends on the demagnetizing factors of the sample and of the grains, N and n, respectively, and on the fraction of superconducting volume, {cauchy integral}, which is itself a field dependent quantity. The structures of the two samples differ in two main properties. The ceramic sample is intrinsically isotropic and contains a significant amount of intergranular material, while the melt textured sample is intrinsically anisotropic and does not contain an appreciable amount of intergranular material. These structural observations lead to significant differences in the field dependence of {cauchy integral} and of the ratio of the magnetic moments, measured with the applied field parallel and perpendicular to the axis of the cylinder.