The Stannides LaRhSn₂ and CeRhSn₂

Abstract

The new stannides LaRhSn2 and CeRhSn2 have been prepared in quantitative yield by reacting the elements in an arc-melting furnace and subsequent annealing at 970 K. Their structures were determined from X-ray single crystal and powder data: Cmcm, a = 460.3(2) pm, b = 1702.9(7) pm, c = 961.3(3) pm, wR2 = 0.0513, 1317 F 2 values, 30 variables for a CeRhSn2 single crystal and a = 463.9(1) pm, b = 1710.0(3) pm, c = 963.7(2) pm, R F = 3.25, 247 F values, 25 parameters for a LaRhSn2 powder sample. Striking structural motifs of LaRhSn2 and CeRhSn2 are distorted RhSn5 square pyramids which are condensed via common tin atoms and via Sn−Sn bonds forming a three-dimensional infinite [RhSn2] polyanion. The latter is characterized by strong Rh−Sn (262−277 pm) as well as Sn−Sn (281 pm) interactions. The cerium atoms fill distorted pentagonal and hexagonal channels within the polyanion. Both crystallographically independent cerium atoms have high coordination numbers: 4Ce + 6Rh + 9Sn for Ce1 and 6Ce + 4Rh + 10Sn for Ce2. Magnetic susceptibility measurements indicate Pauli paramagnetism for LaRhSn2 and Curie−Weiss behavior (2.56(2) μB/Ce) for CeRhSn2. At 4.0(2) K, CeRhSn2 orders ferro- or ferrimagnetically. The experimental saturation magnetization is 0.75(2) μB/Ce at 5.5 T and 2 K. LaRhSn2 and CeRhSn2 are metallic conductors with room-temperature values of 85 ± 20 μΩ cm (LaRhSn2) and 100 ± 20 μΩ cm (CeRhSn2) for the resistivity. The resistance of CeRhSn2 shows a broad minimum near 30 K, possibly suggesting some Kondo-type interactions. Despite the three crystallographically different tin sites the 119Sn Mössbauer spectroscopic measurements show only one signal at δ = 1.93(1) mm/s (LaRhSn2) and δ = 2.01(2) mm/s (CeRhSn2), subjected to quadrupole splitting of ΔE Q = 1.29(1) mm/s (LaRhSn2) and ΔE Q = 1.38(2) mm/s (CeRhSn2).

Structure and Magnetic Properties of CePtZn

“…The magnetization at 5 K and 80 kOe is only 0.70(1) µ B /Ce atom, significantly reduced from the theoretical value for Ce 3+ of 2.14 µ B . Similar magnetic behavior has been observed for HP-CePtSn [13] and CeRhSn 2 [21]. Specific heat data of CePtZn were recorded down to 2 K (Fig.…”

Solid Solutions RE16Rh11–xZx (RE = La, Ce, Pr, Nd, Sm; Z = Ga, Zn, Cd, In, Sn, Sb, Pb, Bi) – Centrosymmetric n = 2 Variants of Parthé’s Homologous Series A5n+6B3n+5

“…Based on this result we can conclude that there is charge transfer from lanthanum not only to the electronegative rhodium, but also to the tin atoms. This is similar to LaRhSn 2 [25], while in other equiatomic RERhSn stannides [37] the isomer shifts are slightly smaller. The 121 Sb spectrum of Pr 16 Rh 9 Sb 2 is presented in Fig.…”

“…The shortest Rh-Sn distance of 346 pm is much longer than the sum of the covalent radii of 265 pm. In the structures of LaRhSn [24], LaRhSn 2 [25], or CaRhSn 2 [26], the rhodium and tin atoms build up three-dimensional [RhSn] and [RhSn 2 ] networks in which the cations fill larger cavities. In those stannides the Rh-Sn distances are the shortest ones.…”

Ferromagnetic Ordering in CeZnSn

“…The saturation magnetization (sm) at 80 kOe amounts to µ exp(sm) = 1.13(1) µ B /Ce atom, significantly reduced from the theoretical one for Ce 3+ at 2.14 µ B /Ce atom. Saturation moments in the range of 1 µ B /Ce atom are frequently observed for similar ternary intermetallics, e. g. CeNiIn 2 [41] or CeRhSn 2 [42]. These small values of the saturation are due to crystal field splitting effects on the J = 5/2 ground state of the Ce 3+ ion.…”