Enhanced interface pinning and aging by high pressure oxygenation of melt textured Nd 1+ xBa 2− xCu 3O 7− δ

Abstract

A competing effect inducing both an enhancement of interface pinning and aging of the critical currents has been established in NdBa 2Cu 3O 7− δ /Nd 4Ba 2Cu 2O 10 (Nd123/422) melt-textured ceramic composites upon high oxygen pressure annealing. We demonstrate that, when high pO 2 treatments are properly chosen, Nd123/422 interfaces become the dominant flux pinning centre, strongly increasing the critical currents at low and intermediate magnetic fields. It is suggested that Nd123/422 interfaces are enriched in antisite defects, which are properly oxygenated only upon high pO 2 annealing. Additional evidence for the enhanced oxygenation is gained from the observation of a consequent decrease of the field induced anomaly at intermediate fields. A second consequence of high pressure oxygenation is the appearance of an aging effect in the critical currents and irreversibility line. This is the first time that aging is described in Nd123/422 ceramic composites.