Flux pinning properties in a GdBa2Cu3O7−δ bulk superconductor with the addition of magnetic alloy particles

Abstract

Pinning stability and the introduction of pinning centers are essential problems inthe application of high temperature superconductors. A study of the role of theaddition of a variety of oxides into Gd-123 bulk superconductors was pursued withrespect to the effect of magnetic pinning centers on enhancement of critical currentdensity. We have found the addition of magnetic alloy particles into Gd-123 bulkcontributes to the enhancement of the critical current density under a magneticfield. The magnetic particles of Fe–B alloy with small amounts of Cu–Nb–Si–Crwere added into the Gd123 matrix and grown into single-domain bulk in air.The effects of Fe–B alloy magnetic particles on the superconducting pinningproperties of Gd123 bulk are reported. The experimental results showed that theTc of the bulk was suppressed significantly and the transition width became larger with anincrease in the doping content of the magnetic particles. This was consistent with magneticimpurities suppressing superconductivity. The critical current density deduced fromthe magnetization as a function of applied external magnetic field was enhancedunder low magnetic field and high magnetic field, which is different from the bulkdoped with paramagnetic particles. Possible mechanisms and the role of magneticmaterials from the viewpoint of increased flux pinning inside the bulk are discussed.