M¨ossbauer Studies on Cation Distributions and Superexchange Interactions in Cu0.2Fe2.8O4

The cation distributions and the superexchange interactions of Cu0.2Fe2.8O4 have been studied by M¨ossbauer spectroscopy and X-ray diffraction. The crystal is found to have a cubic spinel structure with the lattice constant a0 = 8.4007 ± 0.0004 °A. The M¨ossbauer spectra show line broadening in the octahedral (B) site, which is interpreted by probability distribution of cations. The dominant superexchange interaction is found to be an antiferromagnetic intersublattice A-OB superexchange interaction, and its strength is JA−B = −20.7 kB. The intrasublattice A-O-A superexchange interaction is also antiferromagnetic and its strength is JA−A = −9.3 kB. The weakest superexchange interaction is the ferromagnetic B-O-B interaction: JB−B = 0.7 kB. The Debye temperatures of the tetrahedral and the octahedral sites are found to be A = 459 ± 5 K and B = 351 ± 5 K, respectively.