Abstract

A new series of (Cu)(tet)[Cr2-xSnx](oct)S4-ySey compounds was prepared by solid-state reaction at high temperature. Determination of the crystal structures by single-crystal X-ray diffraction revealed that CuCr1.0Sn1.0S2.1Se1.9, CuCr1.2Sn0.8S2.1Se1.9, CuCr1.3Sn0.7S2.2Se1.8, and CuCr1.5Sn0.5S2.2Se1.8 crystallize in a normal spinel-type structure (cubic Fd (3) over barm space group). The powder X-ray diffraction patterns and Rietveld refinements of nominal CuCr2-xSnxS2Se2 (x = 0.2, 0.4, 0.6, 0.8, and 1.0) were consistent with single-crystal X-ray diffraction data. Raman scattering analysis revealed that the A(1g), E-g, and three F-2g vibrational modes were observed in the spectra. The signal at similar to 382 cm(-1), corresponding to the A(1g) mode, is attributed to symmetrical stretching of the chalcogen bond with respect to the tetrahedral metal. The samples with x = 0.2 and 0.4 exhibited ferromagnetic behavior, characterized by large positive theta values of +261 and +189 K, respectively. In contrast, antiferromagnetic (AF) behavior was observed for CuCrSnS2Se2 with a Neel temperature (T-N) of 18.8 K and a theta value of -36.0 K. Density functional theory (DFT) and effective magnetic moments (mu(eff)/mu(theo)) experimentally measured showed that the Sn ion is in oxidation state of 4+, i.e., diamagnetic behavior. DFT calculations revealed that the most stable magnetic state of CuCr1.0Sn1.0S2Se2 was AF with exchange constants for first- and second-neighbor interactions of J(1) = 56.22 cm(-1) and J(2) = 33.88 cm(-1). Thus, the AF interactions between ferromagnetic chains in CuCr1.0Sn1.0S2Se2 originate from the presence of diamagnetic Sn cations.