Intermetallics of the types REPd₃X₂ and REPt₃X₂ (RE=La–Nd, Sm, Gd, Tb; X=In, Sn) with substructures featuring tin and In atoms in distorted square-planar coordination
2019
Engelbert, Simon | Stegemann, Frank | Bönnighausen, Judith | Klenner, Steffen | Janka, Oliver | Pöttgen, Rainer
The intermetallic compounds RET₃X₂ (RE = La–Nd, Sm, Gd, Tb; T = Pd, Pt; X = In, Sn) have been synthesized from the elements by arc-melting and subsequent annealing sequences in tube or induction furnaces. The samples were characterized through Guinier powder diffraction patterns, and several structures were refined from single crystal X-ray diffractometer data. These indium and tin intermetallics crystallize with the orthorhombic CePd₃In₂-type structure, space group Pnma. The palladium (platinum) and indium (tin) atoms in the RET₃X₂ structures build up complex three-dimensional [T₃X₂]ᵟ⁻ polyanionic networks in which the rare earth atoms fill cavities. The striking structural motifs concern the indium, respectively tin substructures, in which part of the indium and tin atoms have distorted square planar homoatomic coordination environments: In1In1₂In2₂ units in PrPd₃In₂ with interatomic distances 325 pm In1–In1 and 332 pm In1–In2 as well as Sn1Sn1₂Sn2₂ units in PrPt₃Sn₂ with the larger distances of 356 pm for Sn1–Sn1 and of 344 pm for Sn1–Sn2. Temperature dependent magnetic susceptibility measurements have indicated Pauli paramagnetism or diamagnetism for the lanthanum compounds, van-Vleck paramagnetism for SmPt₃In₂ and Curie-Weiss paramagnetism for the remaining compounds. Antiferromagnetic ordering was detected at TN = 4.0(1) K for CePt₃In₂ and at TN = 3.5(1) K for SmPt₃In₂. CePt₃In₂ shows a metamagnetic transition at an external magnetic field of 47(3) kOe.
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