Hundredfold Enhancement of Critical Current in Single-Crystal Ba sub 2 YCu sub 3 O sub 7 by Neutron Irradiation

We have obtained a critical current density J sub c ~ 6x10 sup 5 A/cm sup 2 at 77K and 9 kOe in Ba sub 2 YCu sub 3 O sub 7 single crystals by irradiation with fast neutrons. This is two orders of magnitude greater than J sub c in unirradiated crystals, and is markedly superior to results obtained in previous studies of neutron irradiation sup (1-5). This result demonstrates that it is possible to artificially introduce defects into the superconductor to act as flux pinning sites, i.e., that it is possible to solve the problem of low critical current densities in bulk (e.g. melt-textured growth sup (6-8) high-T sub c superconductors.