FLUX-CREEP IN ND1+XBA2-XCU3O7+DELTA (X=0.0-0.1)

Among the REBa2Cu3O7 superconductors, RE=Nd is particularly interesting in that there exists a solid solution Nd1+xBa2-xCu3O7+delta with the solubility limit of 0.04 less-than-or-equal-to x less-than-or-equal-to 0.6 at 890-degrees-C in air and superconductivity appears up to x almost-equal-to 0.4 when it is oxygen-annealed. The substitution of Nd3+ for Ba2+ in Nd1+xBa2-xCu3O7+delta increases the occupation of O(5) sites. For x>0.1, there is a significant depression of T(c) and for x<.0.1, there is no substantial decrease in T(c) within experimental error. While T(c) is not affected over the range 0.0 less-than-or-equal-to x less-than-or-equal-to 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 J(c), but flux creep measurements on high quality powdered and aligned samples of Nd1+xBa2-xCu3O7+delta with 0.0 less-than-or-equal-to x less-than-or-equal-to 0. 1 showed no apparent effects of this substitution on the flux pinning energy.