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 and heavy-ion irradiation (HII). The fast-neutron irradiation introduces spherical cascade defects, whereas the HII creates the columnar defects that extend the entire sample. Dc magnetization measurements and magnetic relaxation 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 relaxation. However, there was a large difference in the observed Jc-B and Fp-B relations, which can be explained in terms of the difference in the defect structure and density. (author)