New Zr6CoAs2-type R6MnSb2 and R6MnBi2 compounds (R=Y, Lu, Dy, Ho)

A powder X-ray diffraction investigation of the new ternary compounds Zr₆CoAs₂-type R₆MnSb₂ and R₆MnBi₂ (R=Y, Lu, Dy, Ho) is reported. The compounds Ho₆MnSb₂ (a=0.8070(2) nm, c=0.4230(1) nm), Lu₆MnSb₂ (a=0.7930(1) nm, c=0.4173(1) nm), Y₆MnBi₂ (a=0.8242(1) nm, c=0.4292(1) nm), Dy₆MnBi₂ (a=0.8211(1) nm, c=0.4286(1) nm), Ho₆MnBi₂ (a=0.8164(1) nm, c=0.4250(1) nm) and Lu₆MnBi₂ (a=0.8019(2) nm, c=0.4185(1) nm) crystallize in the hexagonal Zr₆CoAs₂-type structure (space group P6b2m No. 189). The Zr₆CoAs₂-type structure is a superstructure of the Fe₂P-type structure.     

Crystal structure of new ternary RE1.9Cu9.2Sn2.8 compounds (RE = Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu)

A series of isotypic RE_1.9Cu_9.2Sn_2.8 compounds, where RE are Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, was synthesized by arc-melting and the crystal structure was determined by X-ray powder diffraction. The structure is a partly disordered substitution variant of the CeNi₅Sn structure type (space group P6₃/mmc), which consists of CaCu₅-type fragments of composition RE_0.9Cu_4.2Sn_0.8 and fragments of a hypothetical structure of composition RECu₅Sn₂. All the RE_1.9Cu_9.2Sn_2.8 compounds obtained here are paramagnets and characterized by metal-like conductivity.     

Magnetic structures of R2RhSi3 (R=Ho, Er) compounds

Powder X-ray and neutron diffraction and magnetic measurements have been performed on R₂RhSi₃ (R=Ho and Er) compounds at low temperatures. The compounds crystallize in a derivative of the hexagonal AlB₂-type structure. The crystal structure parameters have been refined on the basis of the X-ray and neutron diffraction patterns collected in the paramagnetic region. These compounds are antiferromagnets with Néel temperatures of 5.2 K for Ho₂RhSi₃ and 5 K for Er₂RhSi₃. Both compounds exhibit collinear magnetic structures, described by the propagation vector k=(1/2,0,0) for Ho₂RhSi₃ and k=(0,0,0) for Er₂RhSi₃. This magnetic order is stable in the temperature range between 1.5 K and the Néel temperature.     

Features of the HDDR process in R–Fe–B ferromagnetic alloys (R is a mixture of Nd, Pr, Ce, La, Dy and others)

Features of the conventional hydrogenation, disproportionation, desorption, recombination (HDDR) and solid-HDDR processes in some R–Fe–B (R is a mixture of Nd, Pr, Ce, La, Dy) ferromagnetic alloys were studied in the temperature range 20–990 °C and pressure range from 1×10⁻³ Pa to 0.1 MPa. This was carried out by means of differential thermal analysis (DTA), X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) methods. The hydride of the initial phase is formed by heating to 115 °C. The disproportionation of the alloys occurs in the temperature range from 320 to 800 °C. Φ-phase constitutes the base of the initial alloys. Among the disproportionation products, R-hydride, -Fe and two borides (Fe₂B and R_1.1Fe₄B₄) were revealed. The initial phase in all the alloys is recovered after heating in vacuum to a temperature of 990 °C. Full hydrogen desorption occurs in two temperature ranges with the peaks at 200–320 and 630–715 °C.     

The crystal structure of R10Co9In20 (R=Er, Tm, Lu) compounds

New ternary indides R₁₀Co₉In₂₀ (R=Er, Tm, Lu) have been found in the systems {Er, Tm, Lu}–Co–In at 870 K. The crystal structure of Tm₁₀Co₉In₂₀ has been refined using single-crystal X-ray data: Ho₁₀Ni₉In₂₀ structure type, P4/nmm space group, Z=2, a=13.166(5) Å, c=9.097(4) Å, V=1577(2) ų, R=0.0315 for 335 unique reflections hkl (DARTCH-1 diffractometer, MoK_α radiation). The coordination polyhedra of the Tm atoms have 16 and 17 vertices, those of the In atoms 12 and 13 vertices and those of the Co atoms 8 and 10 vertices. The structure can be described as a stacking of polyhedra formed by In atoms.     

Magnetic ordering in ternary RMn2Ge2 compounds (R = Tb, Ho, Er, Tm, Lu) from neutron diffraction study

The compounds RMn₂Ge₂ (R = Tb, Ho, Er, Tm, Lu) have been investigated by neutron diffraction. TbMn₂Ge₂ is a collinear ferrimagnet with the Mn and Tb moment aligned along the c axis (μ_TB = 8.81(59) μ_B: μ_Mn = 2.21(44) μ_B). HoMn₂Ge₂ exhibits incommensurale ordering below 2.1 K characterized by two wavevectors at 1.3 K: q₁ = (0.1543(4), 0.1543(4), 0) and q₂ = (0.210(1), 0.007(1), 0). The Mn sublattice remains antiferromagnetic down to 1.3 K (μ_Mn = 2.38(6) μ_B). The Er moments order ferromagnetically below 5.5 K in ErMn₂Ge₂ (μ_Mn = 6.81(31) μ_B). The moments are perpendicular to the c axis. The Mn sublattice remains antiferromagnetic down to 1.8 K (μ_Mn = 2.34(18) μ_B). The magnetic structure of TmMn₂Ge₂ is characterized by the propagation vector (0.0.1/2). the Tm moments lying in the basal plane. The ordering of the Tm moments yields a canting of the Mn moments (τ = 21(3)°); μ_Tm = 6.63(18) μ_B; μ_Mn = 2.28(27) μ_B). The antiferromagnetic structure of LuMn₂Ge₂ has been determined (μ_Mn = 2.32(14) μ_B). The evolution of the magnetic properties of the heavy rare earth compounds RMn₂Ge₂ is discussed.     

Crystal structure of the R3Si1.25Se7 (R = Pr, Nd and Sm) compounds

The crystal structure of new ternary R₃Si_1.25Se₇ (R = Pr, Nd and Sm) compounds (Dy₃Ge_1.25S₇ structure type, Pearson symbol hP22.5, space group P6₃, a = 1.05268 (3) nm, c = 0.60396 (3) nm, R_I = 0.0897 for Pr₃Si_1.25Se₇; a = 1.04760 (3) nm, c = 0.60268 (3) nm, R_I = 0.0891 for Nd₃Si_1.25Se₇; a = 1.04166 (6) nm, c = 0.59828 (6) nm for Sm₃Si_1.25Se₇) was determined using X-ray powder diffraction. The nearest neighbours of the R and Si atoms are exclusively Se atoms. The latter form distorted trigonal prisms around the R atoms, octahedra around the Si1 atoms and tetrahedra around the Si2 atoms. Tetrahedral surrounding exists for Se1 and Se3 atoms. Six neighbours surround every Se2 atom.     

Structural investigation of ternary RIr3B2 compounds (R=Ce and Pr)

Structural studies were performed for the ternary RIr₃B₂ compounds (R=Ce and Pr) from as cast samples. The crystal structure of the ternary boride CeIr₃B₂ (CeCo₃B₂ structure type, space group P6/mmm, a=5.520(3) Å, c=3.066(2) Å, Z=1, V=80.91 ų, ρ_x=15.154 g cm⁻³) was refined to R₁=0.0470, wR₂=0.1240 from single-crystal X-ray diffraction data. The new ternary boride PrIr₃B₂ was found to be isostructural with the CeIr₃B₂ compound. Its lattice parameters a=5.5105(2) Å, c=3.1031(1) Å were obtained from a Rietveld refinement of X-ray powder diffraction data.     

Crystal structure of R3Ge4 compounds (R Er, Ho, Tm, Lu)

The crystal structure of binary germanides R₃Ge₄ (R Er, Ho, Tm, Lu) has been determined by means of powder X-ray diffraction. For Er₃Ge₄ a full-structure determination has been performed using the Rietveld method (306 reflections, space group Cmcm,

Full-size image (2K)

). The location of the atoms in Er₃Ge₄ is similar to that in the W₃CoB₃ structure, with the Ge atoms substituting for Co and B. For the other R₃Ge₄ compounds (RHo, Tm and Lu) the lattice parameters are given.     

Determination of the structure of UFe2Al10 compound

The atomic structure of a new ternary phase UFe₂Al₁₀ appearing in the U–Fe–Al system was determined using direct methods applied to X-ray powder diffraction data. High resolution electron microscopy combined with the methods of crystallographic image processing was used for the verification of the structural model. The UFe₂Al₁₀ phase is orthorhombic and belongs to Cmcm space group, its unit cell contains 40 Al, eight Fe, and four U atoms. The lattice parameters obtained after Rietveld refinement are: a=8.919 Å, b=10.208 Å, and c=9.018 Å. The reliability factors characterizing the Rietveld refinement procedure are: R_p=5.9%, R_wp=8.1%, and R_b=2.9%.     

Crystal structure and magnetic properties of ZnV2O4

We present structural and magnetic data on ZnV₂O₄ single crystals. Single crystal X-ray diffraction shows the measured crystals to be of very high quality, especially with respect to atomic order. The measured magnetic susceptibility resembles to that of a spin glass system, surprising for a translational invariant structure. The results are discussed in the framework of disorder in a magnetically frustrated lattice.     

Crystal structure of the R3Ag1−δSiS7 (R = La, Ce, Pr, Nd, Sm, δ = 0.10–0.23) compounds

The crystal structure of the R₃Ag_1−δSiS₇ (R = La, Ce, Pr, Nd, Sm, δ = 0.10–0.23, space group P6₃, Pearson symbol hP23.80 − 23.54) compounds were determined by means of X-ray single crystal diffraction (a = 1.04168(8) nm, c = 0.57825(4) nm, R1 = 0.0116 for La₃Ag_0.90SiS₇; a = 1.0312(1) nm, c = 0.57395(7) nm, R1 = 0.0152 for Ce₃Ag_0.82SiS₇; a = 1.0248(1) nm, c = 0.57223(5) nm, R1 = 0.0105 for Pr₃Ag_0.85SiS₇; a = 1.0192(1) nm, c = 0.57020(6) nm, R1 = 0.0292 for Nd₃Ag_0.81SiS₇, a = 1.0100(1) nm, c = 0.56643(6) nm, R1 = 0.0208 for Sm₃Ag_0.77SiS₇. Gradual decrease of the silver amount in the series of chalcogenides was found.     

New RRh5Ge3 compounds of the new SmRh5Ge3 structure type and their magnetic properties (R=Sm, Gd, Tb)

Powder X-ray diffraction results and macroscopic magnetic properties of new ternary RRh₅Ge₃ compounds (R=Sm, Gd, Tb) are reported. The compounds SmRh₅Ge₃ (a=2.2744(4) nm, c=0.3888(1) nm), GdRh₅Ge₃ (a=2.2711(5) nm, c=0.3872(1) nm) and TbRh₅Ge₃ (a=2.2628(7) nm, c=0.3851(1) nm) crystallize in the hexagonal SmRh₅Ge₃-type structure (space group P6₃/m; No. 176). The GdRh₅Ge₃ and TbRh₅Ge₃ compounds are Curie–Weiss paramagnets down to 5 K.     

Crystal structure and physical properties of ternary compounds RPt3B, R=La, Pr, Nd

The crystal structure of a new series of ternary rare-earth platinum borides RPt₃B (R=La, Pr, Nd) has been studied by X-ray powder diffraction analyses from the ‘as-cast’ alloys. The tetragonal CePt₃B structure type, space group P4mm (No. 99), has been confirmed for all compounds. Rietveld refinements for the two compounds, PrPt₃B and NdPt₃B, were performed. LaPt₃B is a temperature-independent Pauli-type paramagnet from room temperature down to 4 K. PrPt₃B orders antiferromagnetically at T_N=15 K followed by a ferromagnetic spin flip at T_C=5 K, whereas NdPt₃B exhibits an antiferromagnetic spin alignment at a Néel temperature T_N=7 K. The temperature dependence of the electrical resistivity, ρ(T), reflects the metallic character of these compounds. Furthermore the characteristic changes of slope of ρ(T) plots prove the magnetic transitions.     

The magnetic structures of RMgSn compounds (R = Ce, Pr, Nd, Tb)

The synthesis of the new compounds RMgSn (R = La-Nd, Sm, Gd-Tm, Lu and Y) has been recently reported. The compounds formed by La and Ce crystallise in the TiNiSi structure type (oP12, Pnma), while from Nd they adopt the CeScSi-type (tI12, I4/mmm); PrMgSn is dimorphic: its high-temperature form (HT) is TiNiSi-type while the low-temperature one (LT) is CeScSi-type.In this paper we now report the results of a neutron diffraction investigation which has been performed in order to refine the crystal as well as the magnetic structures for the RMgSn compounds with R = Ce, Pr, Nd and Tb. All these compounds see at low temperature the establishment of long range magnetic ordering with a predominantly antiferromagnetic interaction; only PrMgSn-HT orders ferromagnetically. These results agree with those from magnetic measurements recently reported.The magnetic structure of CeMgSn is of the amplitude-modulated type, the value of the magnetic propagation vector refined at 2 K is τ = [0, 0.1886(4), 0.3384(8)]. The PrMgSn-HT phase below T = 52 K adopts first a purely ferromagnetic structure, then at about T = 15 K a second magnetic coupling leads to a spin-canted magnetic structure. Both PrMgSn-LT and NdMgSn have the same antiferromagnetic commensurate magnetic structure. The TbMgSn compound below T_N = 35 K orders antiferromagnetically with an equal moment cycloidal structure; however a second magnetic transition at a temperature corresponding to T_N2 = 65 K is likely also present.     

Crystal structure, thermal expansion and electrical properties of the new Al0.32ErGe2 compound

A new ternary compound Al_0.32ErGe₂ has been synthesized and studied from 298 K to 773 K using X-ray powder diffraction technique. Its structure has been determined at room temperature by Rietveld refinement of X-ray powder diffraction data. The ternary compound Al_0.32ErGe₂ crystallizes in the orthorhombic with the defect CeNiSi₂ structure type (space group Cmcm, a = 0.40701(2) nm, b = 1.60401(9) nm, c = 0.39240(2) nm, Z = 4 and D_calc = 8.326 g/cm³). The average thermal expansion coefficients , and of Al_0.32ErGe₂ are 1.72 × 10⁻⁵ K⁻¹, 1.11 × 10⁻⁵ K⁻¹ and 1.52 × 10⁻⁵ K⁻¹, respectively. The bulk thermal expansion coefficient is 4.35 × 10⁻⁵ K⁻¹. Electrical resistivity of Al_0.32ErGe₂ was measured between 5 K and 300 K.     

Crystal structures of the Ag4HgGe2S7 and Ag4CdGe2S7 compounds

The crystal structures of the Ag₄HgGe₂S₇ and Ag₄CdGe₂S₇ compounds were investigated using X-ray powder diffraction. These compounds crystallize in the monoclinic Cc space group with the lattice parameters a=1.74546(8), b=0.68093(2), c=1.05342(3) nm, β=93.398(3)° for Ag₄HgGe₂S₇ and a=1.74364(8), b=0.68334(3), c=1.05350(4) nm, β=93.589(3)° for Ag₄CdGe₂S₇. Atomic parameters were refined in the isotropic approximation (R_I=0.0761 and R_I=0.0727, respectively).     

Crystal structure and magnetic behavior of novel R2PdIn8 (R = Pr, Nd, and Sm) compounds

A new series of R₂PdIn₈ intermetallics, where R = Pr, Nd, and Sm, was prepared by arc-melting the constituents under argon atmosphere and studied by means of X-ray diffraction and magnetic measurements. The compounds crystallize with a tetragonal structure of the Ho₂CoGa₈ type (space group P4/mmm). At very low temperatures, they order antiferromagnetically, and the Nd-based indide presumably exhibits an additional magnetic phase transition in the ordered region.     

Structural, thermodynamic, and electrochemical properties of TixZr1−x(VNiCrMnCoAl)2 C14 Laves phase alloys

The crystal structure of the monoclinic phase η-Al₁₁Cr₂ of the space group C2/c, a ≈ 1.76 nm, b ≈ 3.05 nm, c ≈ 1.76 nm, β ≈ 90° [L.A. Bendersky, R.S. Roth, J.T. Ramon, D. Shechtman, Metall. Trans. A 22A (1991) 5] has been determined by single-crystal X-ray diffraction. The structure model, refined to a final R value of 0.0441, has the composition of Al_83.8Cr_16.2. a = 1.77348(10) nm, b = 3.04555(17) nm, c = 1.77344(10) nm, monoclinic angle β = 91.0520(12)°. There are 80 (66Al + 14Cr) independent atomic positions in a unit cell, of which all Cr atom sites and 8 Al atom sites have icosahedral coordination. These icosahedra are interconnected forming icosahedral chains along , (1 0 1) icosahedral layer blocks as well as a three-dimensional icosahedral structure.     

Peculiarities of component interaction in {Gd, Er}-V-Sn Ternary systems at 870 K and crystal structure of RV6Sn6 stannides

The phase equilibria in the Gd-V-Sn and Er-V-Sn ternary systems were studied at 870 K by means of X-ray and metallographic analyses in the whole concentration range. Both Gd-V-Sn and Er-V-Sn systems are characterized by formation of one ternary compound at investigated temperature, with stoichiometry RV₆Sn₆ (SmMn₆Sn₆-type, space group P6/mmm, a = 0.55322(3) nm, c = 0.91949(7) nm for Gd, a = 0.55191(2) nm, c = 0.91869(8) nm for Er). Solubility of the third component in the binary compounds was not observed. Compounds with the SmMn₆Sn₆-type were also found with Dy, Ho, Tm, and Lu, while YV₆Sn₆ compound crystallizes in HfFe₆Ge₆ structure type. All investigated compounds are the first ternary stannides with rare earth elements and vanadium.