Time dependent magnetic response in RBa/sub 2/Cu/sub 3/O/sub 7- delta /: effect of magnetic ordering

High-T/sub c/ superconductors show time-dependent magnetic response due mainly to flux flow. In an investigation of the flux flow at temperatures far above any magnetic transition, no difference was found between the time-dependent response of Y1:2:3 and R1:2:3 (R=Gd, Dy), leading to the conclusion that the paramagnetic susceptibility does not contribute to the time dependence in general. On the contrary, near the antiferromagnetic ordering temperature of Gd1:2:3 and in the region of reduced local moment in Dy1:2:3, an anomalous time dependence is observed which can only be explained by assuming a time-dependent paramagnetic susceptibility. The susceptibility can be interpreted by the assumption of a time-dependent magnetic order parameter, which is an unusual feature of magnetic transitions. A possible explanation is spin-glass-like behavior of the local moments.<
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