Mössbauer studies on cation distributions and superexchange interactions in Cu0.2Fe2.8O4

Abstract

The cation distributions and the superexchange interactions of Cu0.2Fe2.8O4 have been studied by Mossbauer spectroscopy and X-ray diffraction. The crystal is found to have a cubic spinel structure with the lattice constant a 0 = 8.4007 ± 0.0004 ˚A. The Mossbauer 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-O-B superexchange interaction, and its strength is J A−B = −20.7 k B . The intrasublattice A-O-A superexchange interaction is also antiferromagnetic and its strength is J A−A = −9.3 k B . The weakest superexchange interaction is the ferromagnetic B-O-B interaction: J B−B = 0.7 k B . The Debye temperatures of the tetrahedral and the octahedral sites are found to be Θ A = 459 ± 5 K and Θ B = 351 ± 5 K, respectively.