Investigation of Temperature Dependence of the Irreversibility Line of GdBa 2Cu 3O7−δ Added with Nanosized Ferrite ZnFe 2O 4

Abstract

Superconducting samples of the type (ZnFe2O4)xGdBa2Cu3O7−δ were synthesized by the conventional solid-state reaction technique. The nanosized (ZnFe2O4) content x varied from 0 to 0.1 wt% of the samples’ total mass. The prepared samples were characterized using X-ray powder diffraction (XRD) and scanning and transmission electron microscopes (SEM and TEM). The effect of ZnFe2O4 addition, which acts as flux pinning centers, was investigated using ac magnetization at different applied dc magnetic fields. It was found that addition of the nanosized (ZnFe2O4) up to 0.06 wt% enhances the critical current density Jc and the superconducting transition temperature Tc. On the other hand, the superconducting properties of these samples are deteriorated for x > 0.06 wt%. The irreversibility line was thermally activated. The logarithmic plot of Hirr versus (1 − Tirr/ Tc(0)) shows a crossover at about 500 Oe, reflecting the transition from two- to three-dimensional vortex fluctuations. The Birr–T curves are well fitted according to Matsushita’s model, which is based on the de-pinning mechanism caused by thermally activated flux creep. © 2014, Springer Science+Business Media New York.