MOSSBAUER STUDY OF ANTIFERROMAGNETIC CUFES2-XSEX

${\mathrm{CuFeS}}_{2\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Se}}_{\mathit{x}}$ has been studied by M\"ossbauer spectroscopy and x-ray diffraction. The crystal is found to have a tetragonal structure and the lattice constants ${\mathit{a}}_{0}$ and ${\mathit{c}}_{0}$ increase linearly with increasing selenium concentration. It is noteworthy that the replacement of S by Se in the chalcopyrite decreases the strength of both the superexchange interaction and the interatomic binding. As the interatomic distance increases by 1%, the magnetic hyperfine field and the Debye temperature decrease by 0.8 and 6 %, respectively. The iron ions are found to be in ferric states.