Magnetic Properties of the Melilite-Type Oxysulfide SrMnGeSO: Magnetic Interactions Enhanced by Anion Substitution.

The synthesis, crystal structures, photoluminescence, and magnetic properties of the melilite-type oxysulfide SrMnGeSO were investigated. This compound crystallizes in the melilite structure with space group P4̅2m, in which two kinds of anions, S and O, occupy different crystallographic sites in an ordered manner. The temperature dependence of the magnetic susceptibility of SrMnGeSO shows a broad peak due to a two-dimensional magnetic interaction between Mn ions in the ab plane. The specific heat data show that this compound has an antiferromagnetic transition temperature (T = 15.5 K) that is much higher than that of the oxide analogue SrMnGeO (T = 4.4 K). DFT calculations showed that the magnetic interaction is enhanced by covalency in the Mn-S bonding.