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

Abstract

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 T_S; the higher the Cr concentration, the higher the T_S.