Mössbauer study of YBa2(Cu1−xFex)3Oy from an aspect of distribution of Fe

Fe Mössbauer spectra have been measured systematically in YBa₂(Cu_1-xFe_x)₃O_y prepared by two different heat treatments: the usual treatment (O) and the heat treatment including that under lower oxygen fugacity at high temperatures followed by the oxidation process at low temperatures (NO). From the analysis of the results in terms of binomial random probability, it has been found that the Fe distribution in the Cu(1) site is almost random in the heat treatment (O). Here, the D1 and D2 components in the Mössbauer spectra, which have been assigned to the 4 and 6 oxygen coordinated Fe ions in the Cu(1) site respectively, should correspond to the monomer and cluster Fe ions. In the heat treatment (NO), some of the Fe ions are transferred to the Cu(2) site and there exist only cluster Fe ions in the Cu(1) site, resulting in the characteristic change of macroscopic properties of this system.