Structures and Physical Properties of Rare-Earth Chromium Germanides RECrGe 3 (RE = La−Nd, Sm) (original) (raw)
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Inorganic Chemistry, 2012
Reported are the syntheses, crystal structures, and magnetic susceptibilities of two series of closely related rare-earth metal−lithium germanides RE 2 Li 2 Ge 3 and RE 3 Li 4 Ge 4 (RE = La−Nd, Sm). All title compounds have been synthesized by reactions of the corresponding elements at high temperatures, and their structures have been established by single-crystal X-ray diffraction. RE 2 Li 2 Ge 3 phases crystallize in the orthorhombic space group Cmcm (No. 63) with the Ce 2 Li 2 Ge 3 structure type, while the RE 3 Li 4 Ge 4 phases crystallize in the orthorhombic space group Immm (No. 71) with the Zr 3 Cu 4 Si 4 structure type, respectively. Both of their structures can be recognized as the intergrowths of MgAl 2 Cu-and AlB 2-like slabs, and these traits of the crystal chemistry are discussed. Temperature-dependent directcurrent magnetization measurements indicate Curie−Weiss paramagnetism in the high-temperature regime for RE 2 Li 2 Ge 3 and RE 3 Li 4 Ge 4 (RE = Ce, Pr, Nd), while Sm 2 Li 2 Ge 3 and Sm 3 Li 4 Ge 4 exhibit Van Vleck-type paramagnetism. The data are consistent with the local-moment magnetism expected for RE 3+ ground states. At temperatures below ca. 20 K, magnetic ordering transitions have been observed. The experimental results have been complemented by tight-binding linear muffin-tin orbital electronic-band-structure calculations.
Magnetic and Electronic Properties of Selected Rare-Earth Chromium Germanides Compounds
Acta Physica Polonica A, 2015
The ternary rare-earth compounds exhibit interesting physical and structural properties. These structures changing composition and stoichiometry change drastically their magnetic properties. Some of them, based on chromium germanides were studied experimentally concerning their magnetic properties and up to our knowledge they were never studied theoretically explaining nature of their magnetic behaviour. In the presented work the nature and mechanism of the magnetic and electronic properties of rare-earth chromium germanides is presented. The magnetic and electronic properties of RCrGe2 and RCr0.3Ge2 (R = Tb, Dy, Ho or Er) were investigated theoretically applying plane-wave density functional theory/PerdewBurkeErnzerhof methodology. The computational investigations were performed for the stoichiometric and nonstoichiometric crystal structure with the space group Cmcm. The stoichiometry of the rare-earth chromium germanides compounds has signicant eect on the magnetic properties of the investigated material. The theoretical predictions are compared to the experimentally obtained results.
Journal of Physics: Condensed Matter, 2003
A novel ternary structure type has been determined from single crystals of Ce 2 Zn 6 Ge 3 grown from indium-zinc flux solvent. The Ce 2 Zn 6 Ge 3 type is hexagonal (a = 0.767 69(2) nm; c = 0.411 59(2) nm) with space group P62m, Z = 1. Isotypic compounds with La, Pr, Nd, Sm and Gd were synthesized by reaction sintering, and their isotypic crystal structures were confirmed from Rietveld refinements. These novel ternaries show metallic behaviour and their ground state depends on the particular rare earth ion. Long-range magnetic order was deduced for the compounds from Ce to Gd, with a maximum transition temperature T N ∼ 29 K for Gd 2 Zn 6 Ge 3. While the compounds with Ce and Pr exhibit a spontaneous magnetic type of order, those with Nd, Sm and Gd are antiferromagnetic. The magnetic structures of Pr 2 Zn 6 Ge 3 and Nd 2 Zn 6 Ge 3 were resolved on the basis of neutron powder diffraction performed at 1.5 K.
Inorganic Chemistry, 2012
Eight new rare-earth metal−lithium−germanides belonging to the [REGe 2 ] n [RELi 2 Ge] m homologous series have been synthesized and structurally characterized by single-crystal X-ray diffraction. The structures of the title compounds can be rationalized as linear intergrowths of imaginary RELi 2 Ge (MgAl 2 Cu structure type) and REGe 2 (AlB 2 structure type) slabs. The compounds with general formula RE 7 Li 8 Ge 10 (RE = La− Nd, Sm), i.e., [REGe 2 ] 3 [RELi 2 Ge] 4 , crystallize in the orthorhombic space group Cmmm (No. 65) with a new structure type. Similarly, the compounds with general formula RE 11 Li 12 Ge 16 (RE = Ce−Nd), i.e., [REGe 2 ] 5 [RELi 2 Ge] 6 , crystallize in the orthorhombic space group Immm (No. 71) also with its own structure type. Temperature-dependent DC magnetization measurements indicate Curie−Weiss paramagnetism in the high-temperature regime and hint at complex magnetic ordering at low temperatures. The measured effective moments are consistent with RE 3+ ground states in all cases. The experimental results have been complemented by tight-binding linear muffin-tin orbital (TB− LMTO) electronic structure calculations.
Journal of Alloys and Compounds, 2009
Four new rare-earth metal tin germanides with general formulae RE2[SnxGe1−x]5 (RE = Nd, Sm; x ≈ 0.25–0.3) and RE[SnxGe1−x]2 (RE = Gd, Tb; x ≈ 0.2–0.25) have been synthesized from the corresponding elements by high temperature reactions using Sn flux. Their structures have been established from single-crystal and powder X-ray crystallography: orthorhombic space group Cmcm (No. 63) with cell parameters a = 4.1057(6) Å, b = 35.992(5) Å, c = 4.2534(6) Å for Nd2[SnxGe1−x]5; a = 4.0707(8) Å, b = 35.550(7) Å, c = 4.2095(8) Å for Sm2[SnxGe1−x]5; a = 4.2248(11) Å, b = 30.451(8) Å, c = 4.0013(11) Å for Gd[SnxGe1−x]2, and a = 4.1936(13) Å, b = 30.230(9) Å, c = 3.9793(12) Å for Tb[SnxGe1−x]2, respectively. The structures of the two families can be described as being stacking variants of the ZrSi2 and DyGe3 types, respectively. They represent another example of site preferences between two group 14 elements, where the lighter Ge atoms preferentially form zig-zag chains while the square sheets (o...
Synthesis, Structure, Chemical Bonding, and Magnetism of the Series RELiGe2 (RE = La–Nd, Sm, Eu)
Inorganic Chemistry, 2011
This article focuses on the synthesis and the crystal chemistry of six members of a series of rare-earth metal based germanides with general formula RELiGe 2 (RE = La−Nd, Sm, and Eu). The structures of these compounds have been established by single-crystal X-ray diffraction (CaLiSi 2 structure type, space group Pnma, Z = 4, Pearson symbol oP16). The chemical bonding within this atomic arrangement can be rationalized in terms of anionic germanium zigzag chains, conjoined via chains of edgeshared LiGe 4 tetrahedra and separated by rare-earth metal cations. The structure can also be viewed as an intergrowth of AlB 2-like and TiNiSi-like fragments, or as the result of the replacement of 50% of the rare-earth metal atoms by lithium in the parent structure of the REGe monogermanides. Except for LaLiGe 2 and SmLiGe 2 , the remaining four RELiGe 2 phases exhibit Curie−Weiss paramagnetism above about 50 K. In the low temperature regime, the localized 4f electrons in CeLiGe 2 , PrLiGe 2 , and SmLiGe 2 order ferromagnetically, while antiferromagnetic ordering is observed for NdLiGe 2 and EuLiGe 2. The calculated effective magnetic moments confirm RE 3+ ground states in all cases excluding EuLiGe 2 , in which the magnetic response is consistent with Eu 2+ configuration (J = S = 7/2). The experimental results have been complemented by tight-binding linear muffin-tin orbital (TB-LMTO) band structure calculations.
New germanates RCrGeO5 (R = Nd–Er, Y): Synthesis, structure, and properties
New germanates RCrGeO5 (R = Nd–Er, Y): Synthesis, structure, and properties, 2008
The new complex germanates RCrGeO5 (R ¼ Nd–Er, Y) have been synthesized and investigated by means of X-ray powder diffraction, electron microscopy, magnetic susceptibility and specific heat measurements. All the compounds are isostructural and crystallize in the orthorhombic symmetry, space group Pbam, and Z ¼ 4. The crystal structure of RCrGeO5, as refined using X-ray powder diffraction data, includes infinite chains built by edge-sharing Cr+3O6 octahedra with two alternating CrCr distances. The chains are combined into a three-dimensional framework by Ge2O8 groups consisting of two edge-linked square pyramids oriented in opposite directions. The resulting framework contains pentagonal channels where rare-earth elements are located. Thus, RCrGeO5 germanates present new examples of RMn2O5-type compounds and show ordering of Cr+3 and Ge+4 cations. Electron diffraction as well as high-resolution electron microscopy confirm the structure solution. Magnetic susceptibility data for R ¼ Nd, Sm, and Eu are qualitatively consistent with the presence of isolated 3d (antiferromagnetically coupled Cr+3 cations) and 4f (R+3) spin subsystems in the RCrGeO5 compounds. NdCrGeO5 undergoes long-range magnetic ordering at 2.6 K, while SmCrGeO5 and EuCrGeO5 do not show any phase transitions down to 2 K.
Journal of the Less Common Metals
Ternary gallides with the chemical formula RECu,Ga,_. have been synthesized from the elements by arc melting. Characterization by X-ray powder diffraction analysis confirmed isotypism with the crystal structure of BaAI, for all the early rare earth members RE 3 La, Ce, Pr, Nd, Sm and Cd. In case of the solid solution CeCu;Ga, _ x, the homogeneous region at 600 "C has been determined ranging from x = 0.4 to x = 1.7. Similar to CeNi,Ga, _ x, the dependence of the volume and of the c parameter as a function of the copper concentration exhibits a large positive deviation from Vegard's rule. Magnetic behaviour was studied in the temperature range 4.5-900 K. LaCuGa, is weakly temperature dependent. Above LNT the magnetic susceptibilities of the cerium, praseodymium and neodymium and gadolinium compounds essentially correspond to a paramagnetism of the tripositive rare earth elements. SmCuGa, reveals a typical Van-Vleck paramagnetism of closely spaced multiplets (pert = 1.58 pa at 300 K). Magnetic ordering generally occurs below 10 K in the form of antiferromagnetic coupling for the samarium and gadolinium compounds whereas ferromagnetism is observed for the cerium, praseodymium and neodymium alloys.
Zeitschrift für anorganische und …, 2010
The rare earth ruthenium gallides Ln 2 Ru 3 Ga 5 (Ln = La, Ce, Pr, Nd, Sm) were prepared by arc-melting of cold-pressed pellets of the elemental components. They crystallize with a tetragonal structure (P4/mnc, Z = 4) first reported for U 2 Mn 3 Si 5 . The crystal structures of the cerium and samarium compounds were refined from single-crystal X-ray data, resulting in significant deviations from the ideal compositions: Ce 2 Ru 2.31(1) Ga 5.69(1) , a = 1135.10(8) pm, c = 580.58(6) pm, R F = 0.022 for 742 structure factors; Sm 2 Ru 2.73(2) Ga 5.27(2) , a = 1132.95(9) pm, c = 562.71(6) pm, R F = 0.026 for 566 structure factors and 32