Cs(2)Ln(3)CuS(8) (Ln = La-Nd, Sm-Tb): Synthesis, Crystal Structure, and Magnetic and Optical Properties
Résumé
This work reports the preparation of new quaternary sulfides Cs(2)Ln(3)CuS(8) (Ln = La-Nd, Sm-Tb), their original crystal and electronic structures, and their magnetic properties. The sulfides were prepared using a reactive flux method from mixtures of Ln(2)S(3) (EuS), Cs(2)S(6), Cu(2)S, and S. They crystallize in a new type of structure (C2/m space group) and exhibit a layer-like crystal structure, which is a hybrid of those of the ACe(2)CuS(6) series (A = Cs, K) and that of K(2)CeCu(2)S(4). The values of the optical band gap calculated by the Kubelka-Munk equation are in the range of 1.2-2.62 eV depending on the nature of the Ln ion. The Cs(2)Gd(3)CuS(8) compound displays relatively great magnetic refrigerating properties at cryogenic temperature with the mass entropy change (-ΔS(M)) reaching 19.5 J kg(-1) K(-1) at 3.5 K for ΔH = 5 T.
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