Structure, magnetic susceptibility, and specific heat of the spin-orbital-liquid candidate FeSc2S4: Influence of Fe off-stoichiometry

Article

关键词: IRON;    PYRRHOTITE;    SULFIDE;   

DOI  :  10.1103/PhysRevB.96.054417

来源: SCIE

【 摘 要 】

We report structure, susceptibility, and specific heat studies of stoichiometric and off-stoichiometric poly-and single crystals of the A-site spinel compound FeSc2S4. In stoichiometric samples, no long-range magnetic order is found down to 1.8 K. The magnetic susceptibility of these samples is field independent in the temperature range 10-400 K and does not show irreversible effects at low temperatures. In contrast, the magnetic susceptibility of samples with iron excess shows substantial field dependence at high temperatures and manifests a pronounced magnetic irreversibility at low temperatures with a difference between zero-field cooled (ZFC) and field cooled (FC) susceptibilities and a maximum at 10 K, reminiscent of a magnetic transition. Single-crystal x-ray diffraction of the stoichiometric samples revealed a single phase spinel structure without site inversion. In single crystalline samples with Fe excess, in addition to the main spinel phase, a second ordered single-crystal phase was detected with the diffraction pattern of a vacancy-ordered superstructure of iron sulfide, close to the 5C polytype Fe9S10. Specific heat studies reveal a broad anomaly, which evolves below 20 K in both stoichiometric and off-stoichiometric crystals. We show that the low-temperature specific heat can be well described by considering the low-lying spin-orbital electronic levels of Fe2+ ions. Our results demonstrate significant influence of excess Fe ions on intrinsic magnetic behavior of FeSc2S4 and provide support for the spin-orbital liquid scenario proposed in earlier studies for the stoichiometric compound.

【 授权许可】

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