Abstract
Measurements of complex susceptibility of YBa2(Cu1-xFex)3Oy (0 ?? x ?? 0.20) were made in the temperature region of 100-5 K.
Two different methods were adopted to prepare the samples. Group I was prepared by slow cooling from 850°C in flowing oxygen gas. Group II was prepared by heating in flowing nitrogen gas at 800°C for 20 h, followed by slow cooling to room temperature in the same atmosphere and then by annealing in flowing oxygen gas below 400°C for more than 20 h. Comparisons of the results suggest that the samples in group II contain the 90-K phase for all the values of x used. From the present results and our previous works, we think that the clustering of substituted Fe ions takes place in the Cu-1 planes of these samples.
