Chemical insights into the synthesis and properties of polycrystalline and single crystal iron scandium sulfide (FeSc$_{\mathrm{2}}$S$_{\mathrm{4}})$*

Iron scandium sulfide, FeSc$_{\mathrm{2}}$S$_{\mathrm{4}}$, has recently attracted significant theoretical and experimental interest as a candidate spin-orbital liquid. An AB$_{\mathrm{2}}$X$_{\mathrm{4}}$ spinel, FeSc$_{\mathrm{2}}$S$_{\mathrm{4}}$ (space group Fd-3m, No. 227) features a high degree of frustration associated with the Fe$^{\mathrm{2+}}$, which occupies the A-site diamond sublattice and is tetrahedrally coordinated by sulfur. The Fe$^{\mathrm{2+}}$ ion is in a high spin (S$=$2) state, resulting in orbital degeneracy due to a single hole on the $e$ orbitals. We report the strides we have made to produce material in powder and single crystal form, and the relationship between the chemistry and the structural, magnetic, and thermodynamic properties of FeSc$_{\mathrm{2}}$S$_{\mathrm{4}}$.