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Ternary Rare Earth ( RE ) Gold Compounds RE AuCd and RE 2 Au 2 Cd
Author(s) -
Mishra Ratikanta,
Pöttgen Rainer,
Hoffmann RolfDieter,
Kaczorowski Dariusz,
Piotrowski Holger,
Mayer Peter,
Rosenhahn Carsten,
Mosel Bernd D.
Publication year - 2001
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/1521-3749(200106)627:6<1283::aid-zaac1283>3.0.co;2-l
Subject(s) - crystallography , intermetallic , cerium , ternary operation , tantalum , crystal structure , ytterbium , europium , trigonal crystal system , materials science , rare earth , single crystal , chemistry , metallurgy , doping , alloy , luminescence , optoelectronics , computer science , programming language
New intermetallic rare earth compounds RE AuCd ( RE = Y, La–Nd, Sm–Yb) and RE 2 Au 2 Cd ( RE = La, Pr, Nd, Sm) were prepared by reaction of the elements in sealed tantalum tubes in a high‐frequency furnace. The compounds were investigated by X‐ray diffraction both on powders and single crystals. The equiatomic RE AuCd compounds with RE = Y, La–Nd, Sm, and Gd–Tm adopt the ZrNiAl type structure with space group P 62 m . Single crystal X‐ray data yielded a = 786.2(2), c = 415.9(1) pm, wR 2 = 0.0337, 402 F 2 values for LaAuCd and a = 782.91(9), c = 410.01(5) pm, wR 2 = 0.0653, 395 F 2 values for CeAuCd with 14 parameters for each refinement. Geometrical motifs in CeAuCd are two types of gold centered tricapped trigonal prisms: [Au1Cd 3 Ce 6 ] and [Au2Cd 6 Ce 3 ]. The gold and cadmium atoms form a three‐dimensional [AuCd] polyanion in which the cerium atoms fill distorted hexagonal channels. EuAuCd and YbAuCd crystallize with a TiNiSi type structure, space group Pnma : a = 755.2(1), b = 450.59(5), c = 878.6(1) pm, wR 2 = 0.0904, 500 F 2 values for EuAuCd, and a = 731.64(3), b = 432.94(2), c = 875.80(4) pm, wR 2 = 0.1192, 457 F 2 values for YbAuCd with 20 parameters for each refinement. In these structures the europium(ytterbium) and cadmium atoms form zig‐zag chains of egde‐ and face‐sharing trigonal prisms which are centered by the gold atoms. Also in EuAuCd and YbAuCd a three‐dimensional [AuCd] polyanion occurs in which the europium(ytterbium) atoms are embedded. Europium and ytterbium are divalent in EuAuCd and YbAuCd. Susceptibility measurements show Pauli paramagnetism for YbAuCd and Curie‐Weiss behavior above 100 K for EuAuCd with an experimental magnetic moment of 7.86(6) μ B /Eu. Ferromagnetic ordering is detected at 28 K. The saturation magnetic moment is 7.1(1) μ B /Eu at 1.9 K. 151 Eu Mössbauer spectra show an isomer shift of –9.2(2) mm/s and full magnetic hyperfine field splitting at 4.2 K with an internal hyperfine field of 19.5(4) T at the europium nuclei. The RE 2 Au 2 Cd compounds crystallize with the Mo 2 FeB 2 structure, a ternary ordered version of the U 3 Si 2 type. These structures may be considered as an intergrowth of distorted CsCl and AlB 2 related slabs of compositions RE Cd and RE Au 2 . Chemical bonding in RE AuCd and RE 2 Au 2 Cd is briefly discussed.