SUPEREXCHANGE INTERACTIONS IN CU0.5FE0.5RH0.5CR1.5S4

Cu0.5Fe0.5Rh0.5Cr1.5S4 has been studied by Mossbauer spectroscopy, X-r ay diffraction, and magnetization measurement. The crystal is found to have a cubic spinel structure with the lattice constant a(0) = 9.859 +/- 0.005 Angstrom. The iron ions are in ferric states and occupy the tetrahedral sites. The temperature dependence of both the magnetic hyp erfine field and magnetization is explained by the Neel theory of ferr omagnetism using three exchange integrals: J(Fe-Cr)/k(B) = -13.76 K, J (Fe-Fe)/k(B) = -8.08 K, and J(Cr-Cr)/k(B) = 8.53 K. Neel temperature a nd Debye temperature are found to be 288 +/- 2 K and 533 +/- 5 K, resp ectively.