Hyperfine interactions associated with iron substituted superconducting oxides.

摘要

Theoretical and experimental Moessbauer spectroscopy studies have been made concerning charge and spin densities and magnetic hyperfine fields (H(sub hf)) in iron-substituted superconducting oxides. Calculations were carried out in the self-consistent-field embedded cluster model using local density theory (SCF-X(alpha)) with a variational atomic orbital basis. Spectral densities and changes in charge and spin density were monitored around neighboring Cu sites, as well as Fe impurity site, and La(sub 2)Cu(sub 1-x)Fe(sub x)O(sub 4) and YBa(sub 2)Cu(sub 3-x)Fe(sub x)O(sub 7-y) compounds. Moessbauer isomer shifts (IS), quadrupole splittings (QS) and H(sub hf) are obtained by fitting multiline models to the observed spectra and are compared with SCF-X(alpha) results for specific lattice sites. The influence of oxygen vacancies and partial oxygen disorder is modelled and compared with the experimental data on variable oxygen content and disorder. 10 refs., 3 tabs.