Transport and Magnetic Studies of New Mixed-Valence Compounds: K₃Cu₈Se₆, KCu₃Se₂, K₃Cu₈Te₆and BaCuS_3-x

Abstract

New mixed-valent copper chalcogenides BaCuS3_ x and K3Cu8X6 with X = Se or Te and KCu3Se2, with chemical patterns corresponding to the recently investigated K3Cu8S6 and KCu3S2, were synthesized. For these new samples the results of resistivity and magnetic susceptibility measurements are presented. For BaCuS 3 _x , K3Cu8Se6 and KCu3Se2 the metal-insulator transition is observed with the low temperature phase being metallic, which is untypical, whereas K3Cu8Te6 is a metal in the investigated temperature range. The temperature dependence of magnetic susceptibility of the studied samples testifies to their diamagnetic or weakly paramagnetic behaviour.

Copper Vacancies and Heavy Holes in the Two-Dimensional Semiconductor KCu3–xSe2

“…Jacyna-Onyszkiewicz et al , briefly reported the temperature-dependent resistivity of KCu 3– x Se 2 and observed an interesting transition from semiconducting to metallic behavior at ∼160 K. However, the resistivity data contained several erratic steps, and their reproducibility was not discussed. The contact material in that case was not specified, but we observed similar irregular, nonreproducible behavior when Ag paste contacts were used on KCu 3– x Se 2 single crystals.…”

“…Although its crystal structure was unknown, Jacyna-Onyszkiewicz et al briefly reported its temperature-dependent resistivity. 23,24 These data contained unexplained anomalies that bore resemblance to charge-density-wave formation (e.g., as in TiSe 2 25 ) and thus warranted further study. Here we present the synthesis, crystal structure, and optical and electronic properties of KCu 3−x Se 2 .…”

“…With regard to our interest in layered compounds with physical properties related to the A x Fe 2– x Se 2 ( A = alkali metal) superconductors, we discovered the ternary phase KCu 3– x Se 2 . Although its crystal structure was unknown, Jacyna-Onyszkiewicz et al briefly reported its temperature-dependent resistivity. , These data contained unexplained anomalies that bore resemblance to charge-density-wave formation (e.g., as in TiSe 2 ) and thus warranted further study. Here we present the synthesis, crystal structure, and optical and electronic properties of KCu 3– x Se 2 .…”

[CH3NH3]2Ag4SnIV2SnIIS8: An Open-Framework Mixed-Valent Chalcogenidostannate

“…Meanwhile, the chalcogenidometalates with a mixed valence − have received considerable attention due to their unique properties and promising applications in superconductivity, metallic conductivity, charge-density waves, and magnetism . However, hitherto the mixed-valent chalcogenidostannates­(II,IV) have rarely been isolated.…”