Modification of flux pinning properties of RE-Ba-Cu-O superconductor by fast-neutron and heavy-ion irradiation

RE-Ba-Cu-O bulk samples and single crystals were exposed to fast-neutron an d heavy-ion irradiation (HII). The fast-neutron irradiation introduces sphe rical cascade defects, whereas the HII creates the columnar defects that ex tend the entire sample. Dc magnetization measurements and magnetic relaxati on experiments were performed with a SQUID magnetometer to study the effect of radiation-induced defects on flux pinning properties. In both cases, we observed an enhancement of critical current and a decrease of magnetic rel axation. However, there was a large difference in the observed J(c)-B and F -p-B relations, which can be explained in terms of the difference in the de fect structure and density.