Complex Susceptibility of YBa2(Cu1-xFex)3Oy

Abstract
The superconducting transitions of YBa2(Cu1-x Fe x )3O y (0≦x≦0.20) compounds were measured in terms of complex susceptibility, χ= χ' -i χ''. Two groups of samples were prepared. Group I was prepared by slow cooling from 850°C in flowing O2 gas. Group II was prepared by heating in flowing N2 gas at 800°C for 20 h, followed by slow cooling to room temperature in the same atmosphere and then by annealing in flowing O2 gas below 400°C for more than 20 h. Comparisons of the results suggest that the clustering of substituted Fe ions takes place in the Cu1-O planes of the samples in group II, and that the flux motion is restrained.