Orbital Glass in FeCr2S4

TL;DR

This study investigates the low-temperature orbital states of FeCr2S4, revealing an orbital liquid above 10 K and an orbital glass state at lower temperatures, with implications for understanding orbital phenomena in correlated materials.

Contribution

It provides experimental evidence of an orbital liquid and orbital glass state in FeCr2S4, highlighting the impact of stoichiometry and crystal structure on orbital ordering.

Findings

Orbital liquid state exists above 10 K in FeCr2S4.

A transition at 10 K leads to orbital order in polycrystals.

Single crystals exhibit an orbital glass state with T^2 heat capacity dependence.

Abstract

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.