STRUCTURAL, MAGNETIC, AND EPR STUDIES OF BACUO2+X

XRD, magnetic susceptibility, and EPR studies are reported for the BaC uO2+x compound in both the oxygenated and nonoxygenated phases. The XR D analysis has shown essential differences in the disordered part betw een the oxygenated and the nonoxygenated samples. The magnetic suscept ibility measurements have shown strong ferromagnetic intracluster inte ractions among copper ions in the ordered part of the compound. At low temperature, antiferromagnetic intercluster interactions mediated by the disordered part predominate. EPR measurements in both phases have revealed a spectrum of Cu2+ ions, in orthorhombic local symmetry, whic h is attributed to copper ions in the disordered part. An intense exch ange-narrowed EPR line has also been observed in both phases, which is ascribed to the copper clusters in the ordered part. The temperature dependence of the intensity and linewidth of this line is consistent w ith the bulk magnetic behaviour. At low temperature, the divergent beh aviour of the EPR parameters indicates that antiferromagnetic ordering may occur. Additionally, it was found that the EPR spectra are essent ially influenced by thermal treatment and the ordering of the oxygen a toms in the disordered part of the compound. (C) 1995 Academic Press, Inc.