Influence of neutron-irradiation-induced defects on the flux pinning inHgBa2Ca2Cu

Abstract

The influence of fast neutron irradiation on flux pinning in HgBa 2 Ca 2 Cu 3 O 8ϩx single crystals (T c ϭ120 K) subjected to a fluence of 5ϫ10 17 cm Ϫ2 was studied. Magnetic measurements were performed using a commercial superconducting quantum interference device magnetometer and a miniaturized torque magnetometer. In the unirradiated state, the irreversibility line ͑IL͒, plotted as ln(H irr ) vs ln(1ϪT irr /T c ), shows two slopes. At higher temperatures ͑85-100 K͒ the IL is described by a power-law dependence H irr (T)ϭH irr (0) (1ϪT irr /T c ) ␣ with ␣Ϸ2.1. At lower temperatures ͑25-60 K͒, a more rapid change of H irr with temperature is observed, with the exponent ␣Ϸ4.8. Irradiation shifts the IL to significantly higher magnetic fields/ temperatures, where it is rather well described by a single power-law dependence with the exponent ␣Ϸ2.3. The effective mass anisotropy ␥ϭ(m c /m ab ) 1/2 , as determined from torque measurements, decreases after neutron irradiation. The shielding current density as a function of temperature up to 60 K is well approximated by the exponential dependence j s (T)ϭ j s (0)exp(ϪT/T 0 ). Irradiation increases the characteristic temperature T 0 from about 5.9 K ͑in the as-prepared crystal͒ to T 0 ϭ9.4 K, clearly reflecting a slower decay of j s with temperature. Neutron-generated defects significantly increase j s and suppress the ''fishtail effect'' ͑an increase of j s with magnetic field͒, which was present for the unirradiated crystal.

Neutron irradiation of SmFeAsO1−xFx

“…J c decreases monotonically with field. This is strikingly similar to the changes found in single crystalline [20,44] and melt textured [45,46] cuprate superconductors and indicates that pinning in the unirradiated sample is between weak (ordered flux line lattice) and strong (disordered flux line lattice) pinning. Thus, an order-disorder transition takes place at intermediate fields which leads to the second peak (or fishtail effect) in the magnetization curve [22,[47][48][49][50].…”

Neutron Irradiation of Sm-1111

“…J c decreases monotonically with field. This is strikingly similar to the changes found in single crystalline 20,44 and melt textured 45,46 cuprate superconductors and indicates that pinning in the unirradiated sample is between weak (ordered flux line lattice) and strong (disordered flux line lattice) pinning. Thus, an orderdisorder transition takes place at intermediate fields which leads to the second peak (or fishtail effect) in the magnetization curve 22,47,48,49,50 .…”

Superconducting properties of zinc substitution in Tl-2223 phase

“…It is generally accepted that the values of q are related to the dimensionality of Abrikosov vortices. In particular, q ≈ 2 implies they behave as three dimensional (3D) flux lines [29,30] as reported by Batista-Leyva et al [31] for Tl-1223 system, by Tang et al [32] for Tl-1223/Ag, Triscone et al [33] for (Tl, Pb, Bi)(Sr, Ba) 2 Ca 2 Cu 3 O 9−δ superconductors and by Isber et al [23] for TlBa 2 Ca 2 (Cu 3−x Co x )O 9−δ system. Glowacki [34] obtained similar results for different composites.…”