  Low-temperature heat-capacity investigations on the spinel FeCr2S4 with
ferrimagnetic spin order and orbitally degenerated Jahn-Teller active Fe2+ ions
in a tetrahedral crystal field, provide experimental evidence of an orbital
liquid state above 10 K. We demonstrate that the low-temperature transition at
10 K arises from orbital order and is very sensitive to fine tuning of the
stoichiometry in polycrystals. In single crystals the orbital order is fully
suppressed resulting in an orbital glass state with the heat capacity following
a strict T^2 dependence as temperature approaches zero.

Strongly Correlated Electrons;Disordered Systems and Neural Networks