Structure and Properties of α- and β-CeCuSn: A Single Crystal and Mössbauer Spectroscopic Investigation

Abstract

Two modifications of CeCuSn were prepared from the elements: the high-temperature (β ) modification crystallizes directly from the quenched sample, while the low-temperature (α) modification is formed after annealing at 700 • C for one month. Both modifications were investigated by powder and single crystal X-ray diffraction. We find for β -CeCuSn the ZrBeSi-type structure, space group P6 3 /mmc, a = 458.2(1), c = 793.7(2) pm, wR2 = 0.0727, 148 F 2 values, 8 variable parameters. In the case of α-CeCuSn we find the NdPtSb-type structure, space group P6 3 mc, a = 458.4(1), c = 785.8(2) pm, wR2 = 0.0764, 233 F 2 values, 11 variable parameters. The copper and tin atoms build up layers of ordered [Cu 3 Sn 3 ] hexagons. The layers are planar in β -CeCuSn, however, with highly anisotropic displacements of the copper and tin atoms. In α-CeCuSn a puckering effect is observed resulting in a decrease of the c lattice parameter. Both modifications of CeCuSn exhibit antiferromagnetic ordering, but there is a considerable difference in their magnetic behaviour. Anomalies in the physical properties of the α-and β -modifications of CeCuSn have been detected by Mössbauer spectroscopy and magnetic and specific heat measurements, which serve to explain the structure-property relations.

Lithium Mobility in the Stannides Li2CuSn2 and Li2AgSn2

“…The copper atoms have tetrahedral tin coordination with Cu–Sn distances of 264 pm, close to the sum of the covalent radii of 257 pm 30. Such Cu‐Sn distances also occur in related ternary stannides such as CeCuSn31 or AuCuSn 2 32…”

Coloring, Distortions, and Puckering in Selected Intermetallic Structures from the Perspective of Group‐Subgroup Relations

“…Klassengleiche symmetry reductions force the formation of anti‐phase boundaries. This has been studied in detail for the stannides LaCuSn55 and CeCuSn 56. Corresponding compounds with similar problems in the orthorhombic branch are Eu 2 AuGe 3 57 and Yb 2 AuGe 3 58…”

Searching for hexagonal analogues of the half-metallic half-HeuslerXYZcompounds

“…Of the compounds discussed here, ScCuSn and YCuSn are examples for the puckered LiGaGetype structure, whereas LaCuSn is an example of a planar [YZ] 3− (here CuSn 3− ) network [38]. CeCuSn is dimosphic with different degrees of puckering in the low-and hightemperature modifications [46]. Figure 1 compares the crystal structure of a typical cubic half-Heusler compound, (a) F 43m TiNiSn, with the crystal structures of two variants of the hexagonal XYZ compounds discussed here: P 6 3 mc ScCuSn [38], crystallizing in the LiGaGe type structure and the planar P 6 3 /mmc LaCuSn [38].…”