NdBa2Cu3O7-δ (Nd-123) and Y2Ba4Cu8O16 (Y-124) single crystals were sequentially irradiated with fast neutrons and annealed in air at 250 °C. After each treatment the transition temperature (Tc) and the field dependence of the magnetic moment with the field applied parallel to the crystallographic c-axis were measured at various temperatures by SQUID magnetometry. The results are compared with those on a previously investigated YBa2Cu3O7-δ (Y-123) single crystal. The behaviour of the transition temperature is well established for Y-123, i.e. Tc decreases due to irradiation and increases due to annealing. We find a similar effect for Y-124, but a completely different behaviour of Nd-123. The critical current density (Jc) increases for all samples after an irradiation step and becomes smaller after annealing. We show that the influence of the defects created by irradiation on Tc and Jc strongly depends on the as-grown defect structure. Jc after irradiation is rather a function of the neutron fluence since the last annealing step than a function of the overall dose.
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