The transition between antiferromagnetic order and spin-glass state in layered chalcogenides KFeAgCh2 (Ch = Se, S)

KMnCuTe2: a layered antiferromagnetic semiconductor with long metal-metal distance

The magnetic semiconductor in a two-dimensional system is a major subject for both theoretical and experimental investigations. Here we report the synthesis of a new quaternary manganese chalcogenide KMnCuTe₂, which shows layered structure and antiferromagnetic (AFM) semiconducting features. Single crystals of KMnCuTe₂ were obtained using a self-flux method and based on single-crystal X-ray diffraction, KMnCuTe₂ adopts the ThCr₂Si₂-type structure composed of edge-sharing tetrahedral layers separated by K⁺ cations. The Mn and Cu atoms randomly distribute in the centre of tetrahedral units. Attributed to the large radius of Te, KMnCuTe₂ has large lattice parameters (a = 4.3115(3) Å and c = 14.9360(20) Å), leading to a long metal–metal distance (3.049 Å) in the tetrahedral layers. Based on the experiments and theoretical calculations, KMnCuTe₂ exhibits a G-type AFM interaction with the transition temperature at around 225 K and an indirect semiconducting nature with the band gap of 0.95 eV. The magnetic semiconducting property of KMnCuTe₂ is unique in AMnMCh₂ systems (A = Li, Na, K, M = Cu, Ag and Ch = S, Se, Te), which could be associated with the large metal–metal distance. Our work not only highlights the role of metal–metal interactions on regulating the properties of ThCr₂Si₂-type compounds, but also provides a feasible strategy to obtain the layered magnetic semiconductor.

We synthesized a new quaternary telluride KMnCuTe₂ with long metal–metal distance in tetragonal layers, which shows an indirect band gap of 0.95 eV and long-range antiferromagnetic ordering.

Exotic magnetic properties in Zintl phase BaVSe3: a theoretically supported experimental investigation

The magnetic properties of Zintl phase barium vanadium selenide (BaVSe3) were investigated experimentally and theoretically.

Spin fluctuations yield zT enhancement in ferromagnets

Thermal fluctuation of local magnetization intercoupled with charge carriers and phonons offers a path to enhance thermoelectric performance. Thermopower enhancement by spin fluctuations (SF) has been observed before. However, the crucial evidence for enhancing thermoelectric-figure-of-merit (zT) by SF has not been reported until now. Here we report that the SF leads to nearly 80% zT enhancement in ferromagnetic CrTe near and below T_C ∼ 335 K. The ferromagnetism is originated from the collective electronic and localized magnetic moments. The field-dependent transport properties demonstrate the profound impact of SF on the electrons and phonons. Under an external magnetic field, the enhancement in thermopower is suppressed, and the thermal conductivity is enhanced, evidencing the existence of a strong SF. The anomalous thermoelectric transport properties are analyzed based on theoretical models, and a good agreement with experimental data is found. This study contributes to the fundamental understanding of SF for designing high-performance spin-driven thermoelectrics.

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Spin-dependent thermoelectric properties are investigated

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Itinerate ferromagnetism-induced Stoner excitation favors thermoelectric transport

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Spin fluctuation contribution dominates spin-wave to the transport properties in CrTe

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Spin fluctuations boost zT by 80% near and below the transition temperature in CrTe

New layered chromium chalcogenides CsLiCrSe2, RbLiCrS2 and CsLiCrS2: structures and properties

The synthesis and characterization of the first ThCr₂Si₂-type chromium chalcogenides with intimate correlation between Cr concentration and spin-glass transition temperature.