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

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 F-2 values, 44 variables for LaIr2Sn4, a=1840.08(2), b =448.24(4), c=719.6(1) pm, wR2= 0.0215, 1265 F-2 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 F-2 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, PrIIr2Sn4 and NdIr2Sn4 show Curie-Weiss paramagnetism while SmIr2Sn4 exhibits typical van Vieck paramagnetism. Antiferromagnetic ground states were observed for CeIr2Sn4 (T-N =33 K) and SmIr2Sn4 (T-N =3.8 K). Sn-119 Mossbauer spectra show a dose superposition of four sub-spectra which can be distinguished through their isomer shift and the quadrupole splitting parameter.