The RELixSn2 (RE=La–Nd, Sm, and Gd; 0≤x<1) series revisited. Synthesis, crystal chemistry, and magnetic susceptibilities

• The crystal structures of the RELixSn2 (RE=La–Nd, 0≤x<1) compounds are revised using single-crystal X-ray diffraction data.
• The structure is a filled derivative of the ZrSi2 structure type or defect variant of the CeNiSi2 structure type.
• SmSn2 is isotypic with the ZrGa2 structure, while RESn2 (RE=Gd–Lu) are isotypic with the ZrSi2 structure.

This study is concerned with the ternary compounds RELixSn2 (RE=La–Nd, Sm, and Gd; 0≤x<1), which have been previously thought to be the stoichiometric RELiSn2 phases. These materials crystallize with the base-centered orthorhombic space group Cmcm (No. 63), and can be formally assigned with the CeNiSi2 structure type (Pearson symbol oC16). Our systematic single-crystal X-ray diffraction studies revealed substantial Li-deficiencies in all cases, with SmSn2 (space group Cmmm, ZrGa2 structure type, Pearson symbol oC12) and GdSn2 (space group Cmcm, ZrSi2 structure type, Pearson symbol oC12) being completely lithium-free. The structure refinements also uncovered positional disorder on the Sn site neighboring the vacancies. The Sn-disorder and the Li-deficiency correlate, and vary monotonically with the decreased size of the rare-earth atoms in the order RE=La–Nd. The SmSn2 and GdSn2 structures are devoid of any disorder. Temperature-dependent studies of the magnetic response of the title compounds are also presented and discussed.

RELixSn2 (RE=La–Nd, 0≤x<1) crystallize in a defect variants of the CeNiSi2 structure type (a). The Sn-disorder and the Li-deficiency correlate, and vary monotonically with the decreased size of the rare-earth atoms in the order RE=La–Nd. The SmSn2 (b) and GdSn2 (c) structures are devoid of any disorder.Figure optionsDownload as PowerPoint slide