Magnetic and superconducting properties of RuSr2Gd1.5Ce0.5Cu2O10-delta samples: Dependence on the oxygen content and aging effects

The magnetic and superconducting properties of RuSr2Gd1.5Ce0.5Cu2O10-delta polycrystalline samples with different oxygen-doping levels are presented. A strong suppression of the superconducting temperature (T-c), as well as a reduction in the superconducting fraction, occurs as the oxygen content is reduced by annealing the samples in oxygen-deprived atmospheres. Drastic changes in the electrical resistivity are observed above T-c, possibly associated with oxygen removal, mainly from grain boundaries. However, the magnetic ordering is relatively less affected by the changes in oxygen content of the samples. The spin-glass transition is enhanced and shifted to higher temperatures with the reduction in oxygen content. This could be correlated with an increase in the spin disorder and frustration for the oxygen-depleted samples. Also, the same oxygen-vacancy-induced disorder could explain the reduction in the fraction of the sample showing antiferromagnetic order. We also report significant changes in the measured properties of the samples as a function of time.711