Spin and Orbital Frustration inMnSc2S4andFeSc2S4

Abstract

Crystal structure, magnetic susceptibility, and specific heat were measured in the normal cubic spinel compounds ${\mathrm{MnSc}}_2{\mathrm{S}}_4$ and ${\mathrm{FeSc}}_2{\mathrm{S}}_4$. Down to the lowest temperatures, both compounds remain cubic and reveal strong magnetic frustration. Specifically the Fe compound is characterized by a Curie-Weiss (CW) temperature ${\Theta }_{\mathrm{CW}}=-45\mathrm{K}$ and does not show any indications of order down to 50 mK. In addition, the Jahn-Teller ion ${\mathrm{Fe}}^{2+}$ is orbitally frustrated. Hence, ${\mathrm{FeSc}}_2{\mathrm{S}}_4$ belongs to the rare class of spin-orbital liquids. ${\mathrm{MnSc}}_2{\mathrm{S}}_4$ is a spin liquid for temperatures $T>T_N\approx 2\mathrm{K}$.