Influence of Nd < inf > 4 < /inf > Ba < inf > 2 < /inf > Cu < inf > 2 < /inf > O < inf > 10 < /inf > phase inclusions on flux penetration in melt-textured NdBa < inf > 2 < /inf > Cu < inf > 3 < /inf > O < inf > 7-δ < /inf > superconductors

Abstract

NdBa2Cu3O7-δ superconductor is processed with varying Nd4Ba2Cu2O10 (Nd-422) content, thereby varying systematically its microstructure. The samples are then investigated by studying the flux penetration into the samples as a function of magnetic field using a flat-band lock-in technique. Unlike in sintered samples, the flux profiles in the melt-processed samples are found to be linear, whose slopes increase with increasing Nd-422 content. The slope of the profile gives a direct, model-independent measure of the critical current density in the materials, and the specimens measured can be large enough to include several millimeter-sized domains. The critical current densities thus obtained are compared with those obtained using SQUID magnetometer, wherein the samples have to be much smaller and mostly single domain. The extent of flux penetration, reversible penetration depth, and the slope changes in the flux profiles at high fields are correlated to the micro structural features of the melt-textured samples. © 1998 Published by Elsevier Science B.V. All rights reserved.