CHARACTERIZATION OF YBA2CU3O7, INCLUDING CRITICAL CURRENT-DENSITY JC, BY TRAPPED MAGNETIC-FIELD

Spatial distributions of persistent magnetic field trapped by sintered and melt-textured ceramic-type high-temperature superconductor (HTS) samples have been studied. The trapped field can be reproduced by a model of the current consisting of two components: (i) a surface current J(s) and (ii) a uniform volume current J(v). This J(s) + J(v) model gives a satisfactory account of the spatial distribution of the magnetic field trapped by different types of HTS samples. The magnetic moment can be calculated, based on the J(s) + J(v) model, and the result agrees well with that measured by standard vibrating sample magnetometer (VSM). As a consequence, J(c) predicted by VSM methods agrees with J(c) predicted from the J(s) + J(v) model. The field mapping method described is also useful to reveal the granular structure of large HTS samples and regions of weak links.