Flux creep in Nd1+χBa2−χCu3O7+δ (χ=0.0−0.1)

Abstract

Among the REBa2Cu3O7 superconductors, RE=Nd is particularly interesting in that there exists a solid solution Nd1+χBa2−χCu3O7+δ with the solubility limit of 0.04≤χ≤0.6 at 890°C in air and superconductivity appears χ≈0.4 when it is oxygen-annealed. The substitution of Nd3+ for Ba2+ in Nd1+χBa2−χCu3O7+δ increases the occupation sites. For χ>0.1, there is a significant depression of Tc and for χ<.0.1, there is no substantial decrease in Tc within experimental error. While Tc is not affected over the range 0.0≤χ≤0.1, the oxygens surrounding the substituted Ba sites are expected to locally suppress the superconducting order parameter. Such a local suppression of the order parameter may be expected to act as a pinning site for magnetic flux enhancing the critical current density. Hysteresis measurements exhibited a small increase in the magnetic Jc, but flux creep measurements on high quality powdered and aligned samples of Nd1+χBa2−χCu3O7+δ with 0.0≤χ≤0.1 showed no apparent effects of this substitution on the flux pinning energy.