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

We report the synthesis, crystal structures and physical properties of three quaternary compounds CsLiCrSe2, RbLiCrS2 and CsLiCrS2, which represent the first discovered ThCr2Si2-type chromium chalcogenides. They all share the same structure with the space group I4/mmm and Cr/Li mixed occupancy without ordering. Specifically, the Cr/Li-S bond length in RbLiCrS2 is found to be close to the low limit of known Cr-S bonds, and so only alkali metals Cs and Rb that are large enough in size can achieve lattice match and form these chromium compounds. Resistivity and magnetic measurements on CsLiCrSe2 and RbLiCrS2 single crystals and CsLiCrS2 powder crystals demonstrate that these compounds are semiconducting and exhibit a spin-glass state at low temperatures. A limited solid solution range exists in the close vicinity of Cr : Li = 1 : 1 for all three compounds. Cr concentration is found to play a vital role in affecting the spin-glass transition temperature TS; the higher the Cr concentration, the higher the TS.