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The stannides REIr₂Sn₄ (RE=La, Ce, Pr, Nd, Sm)

Engelbert, Simon, Niepmann, Dirk, Block, Theresa, Heletta, Lukas, Pöttgen, Rainer
Zeitschrift für Naturforschung 2018 v.73 no.11 pp. 875-884
X-radiation, containers, crystallization, ferrimagnetic materials, isomers, melting, niobium, paramagnetism, solid solutions, temperature
The stannides REIr₂Sn₄ (RE=La, Ce, Pr, Nd, Sm) were synthesized from the elements by arc melting or by induction melting in sealed niobium containers. They crystallize with the NdRh₂Sn₄ type structure, space group Pnma. The samples were characterized by powder X-ray diffraction (Guinier technique). Three structures were refined from single-crystal X-ray data: a=1844.5(2), b=450.33(4), c=716.90(6) pm, wR2=0.0323, 1172 F² values, 44 variables for LaIr₂Sn₄, a=1840.08(2), b=448.24(4), c=719.6(1) pm, wR2=0.0215, 1265 F² values, 45 variables for Ce₁.₁₃Ir₂Sn₃.₈₇, and a=1880.7(1), b=446.2(1), c=733.0(1) pm, wR2=0.0845, 836 F² values, 45 variables for Ce₁.₆₈Ir₂Sn₃.₃₂. The structures consist of three-dimensional [Ir₂Sn₄] polyanionic networks in which the rare earth atoms fill pentagonal prismatic channels. The striking structural motif concerns the formation of solid solutions RE₁₊ₓIr₂Sn₄₋ₓ on the Sn4 sites, which have similar coordination as the RE sites. Temperature dependent magnetic susceptibility measurements revealed diamagnetic behavior for LaIr₂Sn₄. CeIr₂Sn₄, PrIr₂Sn₄ and NdIr₂Sn₄ show Curie-Weiss paramagnetism while SmIr₂Sn₄ exhibits typical van Vleck paramagnetism. Antiferromagnetic ground states were observed for CeIr₂Sn₄ (TN=3.3 K) and SmIr₂Sn₄ (TN=3.8 K). ¹¹⁹Sn Mössbauer spectra show a close superposition of four sub-spectra which can be distinguished through their isomer shift and the quadrupole splitting parameter.