DC MAGNETIZATION OF RANDOM Y1BA2CU3O8-DELTA-AG BULK COMPOSITES

It is commonly believed that high-field magnetization measurements of superconducting/normal metal bulk composites probe only the intragranu lar nature of the superconducting constituent. According to this view, the measured magnetic moment divided by the volume of superconducting material should be independent of the volume fraction of superconduct or. we have tested this hypothesis by measuring the dc magnetization a t 10K in magnetic fields to 5T of a series of YBCO/Ag bulk composites with 0 less-than-or-equal-to p less-than-or-equal-to 1.0, where p is t he volume fraction of superconductor. We find that the magnetization h ysteresis curves for p greater-than-or-equal-to 0.70 are nearly identi cal, while those for the p < 0.70 samples fall inside the p greater-th an-or-equal-to 0.70 curves. Two possible interpretations are (i) that variations in Ag content alters the superconducting properties of indi vidual YBCO grains, and (ii) that the p-dependent variations in the YB CO clusters affects the demagnetization factor for samples with p < 0. 70.