New layered chromium chalcogenides CsLiCrSe2, RbLiCrS2 and CsLiCrS2: structure and properties
We report the synthesis, crystal structure 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 space group I4/mmm and Cr/Li mixed occupation without ordering. Specifically, the Cr/Li-S bond length in RbLiCrS2 is found close to the low limit of known Cr-S bonds, so that only alkali metals Cs or Rb are large enough in size to 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 spin-glass state at low temperatures. A limited solid solution range exists in the close vicinity of Cr:Li= 1:1 for all the three compounds. The 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.