(Cu)(tet)(Cr2-xSnx)(oct)S4-ySey Spinels: Crystal Structure, Density Functional Theory Calculations, and Magnetic Behavior
Abstract
A new series of (Cu)[CrSn]SSe compounds was prepared by solid-state reaction at high temperature. Determination of the crystal structures by single-crystal X-ray diffraction revealed that CuCrSnSSe, CuCrSnSSe, CuCrSnSSe, and CuCrSnSSe crystallize in a normal spinel-type structure (cubic 3 space group). The powder X-ray diffraction patterns and Rietveld refinements of nominal CuCrSnSSe ( = 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 , , and three vibrational modes were observed in the spectra. The signal at ∼382 cm, corresponding to the mode, is attributed to symmetrical stretching of the chalcogen bond with respect to the tetrahedral metal. The samples with = 0.2 and 0.4 exhibited ferromagnetic behavior, characterized by large positive θ values of +261 and +189 K, respectively. In contrast, antiferromagnetic (AF) behavior was observed for CuCrSnSSe with a Néel temperature () of 18.8 K and a θ value of -36.0 K. Density functional theory (DFT) and effective magnetic moments (μ/μ) 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 CuCrSnSSe was AF with exchange constants for first- and second-neighbor interactions of = 56.22 cm and = -33.88 cm. Thus, the AF interactions between ferromagnetic chains in CuCrSnSSe originate from the presence of diamagnetic Sn cations.