Characterization of YBa2Cu3O7, including critical current density J c, by trapped magnetic field

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Abstract
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 Js and (ii) a uniform volume current Jv. This Js + Jv 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 Js + Jv model, and the result agrees well with that measured by standard vibrating sample magnetometer (VSM). As a consequence, Jc predicted by VSM methods agrees with Jc predicted from the Js + Jv model. The field mapping method described is also useful to reveal the granular structure of large HTS samples and regions of weak links.