HIGH CRITICAL CURRENT DENSITY IN NEUTRON-IRRADIATED BULK YBa2Cu3O7

Abstract

Bulk melt-textured YBa 2 Cu 3 O 7 irradiated by fast neutrons has been investigated. We observed: (1) a critical current density (Jc) determined magnetically at 77 K exceeds 5×105 A/cm 2 in 0.1 T, 2×105 A/cm 2 in 1 T, and 1.2×103 A/cm 2 in 5.0 T; (2) at 5 K, Jc is >2.1×107 A/cm 2 in 0.5 T, ~1.8×107 A/cm 2 at 1 T and >8×106 A/cm 2 in 5.0 T and (3) the Jc-anisotropy decreases rapidly with the external field (H), e.g. at 77 K, it becomes 1 at ~4.8 T with Jc ~3×103 A/cm 2. We also found that (1) such a Jc-enhancement is most effective in low H but less so in high H, (2) the enhancement is temperature independent at low H, (3) the pinning potential remains unchanged to within ~10% as Jc varies by a factor of 15, and (4) thermal annealing up to 600°C recovers the un-irradiated state. These results and their implications are presented and discussed.