Crystal Structures and Properties of the Thiostannates Eu₂SnS₄ and Sr₂SnS₄ and the Selenogermanate γ‐Sr₂GeSe₄

Abstract

Abstract Eu 2 SnS 4 , Sr 2 SnS 4 , and Sr 2 GeSe 4 have been synthesized by heating the elements or binary precursors at 1073 K and their crystal structures were determined by single crystal methods. Eu 2 SnS 4 crystallizes with a new structure type ( Pnma , a = 11.187(2), b = 8.768(2), c = 7.538(2)Å, Z = 4), consisting of distorted [SnS 4 ] 4— tetrahedra and sevenfold coordinated Eu 2+ ions. Sr 2 SnS 4 and γ‐Sr 2 GeSe 4 are isostructural and form a new structure type likewise ( Ama 2, Z = 4, Sr 2 SnS 4 : a = 9.977(1), b = 10.311(2), c = 7.243(1)Å, Sr 2 GeSe 4 : a = 10.284(2), b = 10.543(2), c = 7.411(1)Å) with more regular tetrahedral anions and strontium coordinated by seven and eight chalcogen atoms, respectively. Eu 2 SnS 4 is a Curie‐Weiss paramagnet (7.80(2) μ B /Eu; θ = 4.2(2) K) and orders antiferromagnetically at T N = 5.5(2) K with a magnetization of 6.56(5) μ B /Eu at 5.5 T. The divalent nature of europium is also evident from 151 Eu Mössbauer spectra which show a single signal at an isomer shift of —12.2(1) mm/s at 78 K. Full magnetic hyperfine field splitting (19.5(2) T at the europium nuclei) is observed at 4.2 K. The 119 Sn spectrum shows one signal at 1.25(9) mm/s subject to quadrupole splitting of 0.76(2) mm/s. At 4.2 K a transferred hyperfine field of 3(1) T is detected at the tin site.