Physical properties of quaternary mixed transition metal sulfides: ACuFeS2 (A = K, Rb, Cs)

Three quaternary sulfides ACuFeS2 (A = K, Rb, Cs) with the ThCr2Si2-type structure were prepared from alkali metal carbonate A2CO3, Fe2O3, and CuO by CS2/N2 sulfurization. All of the samples show semiconducting behavior. Magnetic susceptibility data indicate the presence of localized moment arising from the di- and trivalent iron ions. The semiconducting properties observed in this system are in contrast to the metallic behavior predicted by theoretical calculations.