Structure and magnetic properties of TbFe10.5−x MnxMo1.5 compounds

The effects of Mn partial substitution for Fe in TbFe_10.5Mo_1.5 on the structure and magnetic properties were investigated. TbFe_10.5−xMn_xMo_1.5 samples (x = 1.5, 2.0, 3.0, 4.0, 5.0) were prepared by means of arc-melting and subsequent vacuum annealing. The structure and magnetic properties of TbFe_10.5−xMn_xMo_1.5 compounds were investigated by X-ray powder diffraction and magnetic properties measurements. The following conclusions were obtained: all the TbFe_10.5−xMn_xMo_1.5 compounds studied crystallize in the ThMn₁₂-type structure; the unit-cell volume increases monotonically with increasing Mn concentration; a compensation temperature was observed in the magnetization-temperature curve of TbFe_7.5Mn₃Mo_1.5 compounds. With increasing Mn concentration, the saturation magnetization at 4.4 K decreases to zero, and then increases again, the magnetic moments of the transition-metal sublattice of TbFe_10.5−xMn_xMo_1.5 compounds decrease monotonically.     

New Zr6CoAs2-type compounds: Y6CoBi2, Ho6CoBi2 and Tm6CoBi2

Results of a powder X-ray diffraction investigation of new ternary compounds are reported. The compounds Y₆CoBi₂ [a=0.8312(1) nm, c=0.4144(1) nm], Ho₆CoBi₂ [a=0.8246(2) nm, c=0.4095(1) nm], and Tm₆CoBi₂ [a=0.8155(2) nm, c=0.4066(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, magnetic behaviour and valence state of ytterbium in the Yb4Ni10+xGa21−x phase

The ternary phase Yb₄Ni_10+xGa_21−x has been synthesised from the elements by high frequency melting in argon atmosphere. The homogeneity region has been established from X-ray powder data and confirmed by EDX analysis for 0.3≤x≤1. The crystal structure of Yb₄Ni_10+xGa_21−x has been estimated from X-ray single crystal data: space group C2/m (no. 12), Z=2, a=20.6815(9) Å, b=4.0560(4) Å, c=15.3520(7) Å, β=124.800(3)°, R(F)=0.023 for 1701 symmetry independent reflections with F(hkl)>4σ(F). A special feature of the structure is the local disorder within the gallium/nickel network. Neglecting atomic disorder in the region of the Ga9 and Ga11 positions, the Yb₄Ni_10+xGa_21−x structure is an occupation variant of the Ho₄Ni₁₀Ga₂₁ type with nickel atoms partially replacing the Ga atoms in the 2d sites at the centers of distorted icosahedra. From magnetic susceptibility and from L_III-XAS spectra, the valence state of ytterbium is near 3+.     

Crystal structure of Zr9Co7In14

Zr₉Co₇In₁₄ crystallizes in the cubic system, space group Fm3m, a = 13.300(2) Å Z = 2, R = 0.0412 for 567 unique reflection (KM-4 diffractometer, Mo K radiation). The crystal structure, related to the Cr₂₄C₆ -type structure, can be described as a stacking of columns of cubes, tetragonal antiprisms, and cubo-octahedrons extending along the coordinate axes. One of the ln atoms is coordinated by a Frank-Kasper polyhedron.     

A substitution of nickel by antimony:: Crystal and electronic structure of the new antimonide Hf6Ni1−xSb2+x

The ternary antimonides Hf₆M_1−xSb_2+x (M=Fe, Co, Ni) were prepared by arc-melting of stoichiometric mixtures of Hf, HfSb₂ and M. According to the single crystal structure analyses, performed on Hf₆NiSb₂ and Hf₆Ni_0.76Sb_2.24, Hf₆M_1−xSb_2+x crystallizes in an ordered variant of the Fe₂P structure type with the M and Sb atoms occupying the two P positions on 1b and 2c of space group P

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2m, respectively (Zr₆CoAl₂ type). The 3d metal atoms M can partially be replaced by antimony, leading to significant, anisotropic changes in the lattice dimensions which are a=765.6(1) pm, c=362.10(7) pm, V=183.81(5)×10⁶pm³ for Hf₆NiSb₂, and a=760.5(1) pm, c=372.40(7) pm, V=186.53(5)×10⁶pm³ for Hf₆Ni_0.76Sb_2.24 as determined by single crystal data. Calculations of the electronic structure of Hf₆NiSb₂ using the Extended Hückel approximation show strong bonding Hf–Hf, Hf–Ni, and Hf–Sb interactions.     

Crystal structure of the new ternary aluminide CeRu3−xAl10+x (x = 0.17)

A large and transparent Yb³⁺:GdYCOB crystal with dimensions up to 30 mm× 58 mm have been grown by the Czochralski method. The spectral properties of Yb³⁺:GdYCOB crystal has been investigated. The absorption cross-section (σ_a) is 1.65 × 10⁻²⁰ cm² at 977 nm. The emission cross-section (σ_e) is 0.25 × 10⁻²⁰ cm² with an FWHM of 37.2 nm at 1020 nm. The fluorescence lifetime is 3.00 ms.     

Structure and magnetic properties of Gd3(Fe1−xTix)29 (x=0.011–0.034)

Single-phase compounds Gd₃(Fe_1−xTi_x)₂₉ (x=0.0110.034) have been synthesized. Gd₃(Fe_1−xTi_x)₂₉ crystallises in a monoclinic lattice with space group P2₁/c, and the crystal structure is refined by the Rietveld technique based on X-ray powder diffraction data. Thermomagnetic analysis indicates that the Curie temperature of the compounds ranges from 517 K to 538 K. The saturation magnetizations of the Gd₃(Fe_1−xTi_x)₂₉ (x=0.011, 0.022, 0.034) at 1.5 K are 103.6, 102.0 and 94.3 Am²/kg, and the anisotropy fields at 1.5 K are 6.0, 6.2 and 6.4T, respectively.     

Crystal structures of new ternary rare earth silicides Sc3Pr2Si4, Sc1.26Pr3.74Si4 and Sc3.96Nd1.04Si4 with ordered and partially ordered rare earth sites

The crystal structures of three new ternary silicides Sc₃Pr₂Si₄, Sc_1.26Pr_3.74Si₄ and Sc_3.96Nd_1.04Si₄ were determined by single crystal X-ray diffraction. The title compounds crystallize with three different substitution derivatives of the Sm₅Ge₄ structure type (orthorhombic space group Pnma) containing various distributions of rare earth atoms on the three Sm sites. Crystal chemistry analysis shows that these distributions are controlled by the atomic size factor.     

Structural and magnetic properties of Sm2Fe17−xCrxC2 nanocrystalline carbides with 0≤x≤2

The crystallographic and the Curie temperature of the Sm₂Fe_17−xCr_xC₂ (x=0.5, 1, 1.5 and 2) carbides have been extensively studied. X-ray diffraction studies have shown that all these alloys are approximately single phases corresponding to the Th₂Zn₁₇ type rhombohedral structure with a small amount of -Fe. The amount of this residual -Fe phase decreases with increasing the Cr atomic content. It decreases from 1 wt% for x=0.5 to 0.4 wt.% for x=2. The lattice parameter c increases as a function of the Cr atomic content x from x=0 to x=1.5 and then decreases. This is due to the Cr atoms which prefer to substitute the Fe atoms in the 6c sites located along the c-axis. The lattice parameter a and the unit-cell volume decrease in all substitution ranges. The insertion of the C atoms leads essentially to an increase of the distances between the 9d and 18h sites and the 9d–18f sites. The Curie temperature reaches a maximum value of 583 K for x=1.5 and then decreases to 551 K for x=2. The enhancement of the T_c for lower Cr contents is due to a lowering of the hybridization of the iron atoms with their neighbors, the magnetovolume effect and the reduction of antiferromagnetic interactions. However, the decrease in T_c for higher Cr content is due to the reduction in the number of Fe–Fe pairs due to the magnetic dilution effect. For given interatomic distances, the exchange coupling of the Cr–Cr atoms is not of antiferromagnetic type and the exchange integral of the Cr–Cr pair is higher than that of the Fe–Fe pair.     

Influence of hydrogenation on structure and magnetic properties of HoFe11−xCoxTi

Magnetic properties and crystal structure of the hydrides of ferromagnetic compounds HoFe_11−xCo_xTi (x = 1, 2, 4, 6, 7, 11) are investigated. The crystal structure was determined by X-ray diffraction (XRD) analysis and the magnetization was measured in applied magnetic fields up to 10 T and at temperatures ranging from 5 K to room temperature. Results show that the crystal structure of the hydrides is the same as for parent compounds but with a moderate unit cell increase. Other properties such as saturation magnetization are affected by H insertion within the lattice. The effect of hydrogenation on magnetic anisotropy energy leads to disappearance of the FOMPs observed in the parent compounds.     

Ba4In2−x(CO3)1+xO6−2.5x and Ba4In0.8Cu1.6(CO3)0.6O6.2—new indium oxycarbonates closely related to n=3 Ruddlesden–Popper phases

Investigations of phase relations in the Ba-rich part of the In₂O₃–BaO(CO₂)–CuO pseudo-ternary system at 900 °C have revealed the existence of new indium–copper oxycarbonate – Ba₄In_0.8Cu_1.6(CO₃)_0.6O_6.2. Rietveld refinement of the X-ray powder diffraction data combined with infrared studies gives evidence that this phase is a oxycarbonate crystallising in the tetragonal structure (space group I4/mmm) with unit cell parameters: a=4.0349(1) Å and c=29.8408(15) Å. In the binary part of the In₂O₃–BaO(CO₂) system we have identified the occurrence of Ba₄In_2−x(CO₃)_1+xO_6−2.5x oxycarbonate solid solution showing a crystal structure also described by I4/mmm space group, but with the unit cell parameters: a=4.1669(1) Å and c=29.3841(11) Å for x=1. The existence range of this phase, −0.153<x<0.4, includes chemical compositions of earlier found phases: Ba₅In_2+xO_8+0.5x with 0≤x≤0.45 (known as the -solid solution), as well as the binary Ba₄In₂O₇ phase. The crystal structures of both new oxycarbonates are isomorphic and related to n=3 member of the Ruddlesden–Popper family.     

High temperature transformations of the Au7Cu5Al4 shape-memory alloy

The β-phase of Au₇Cu₅Al₄ undergoes a reversible shape-memory phase transformation, however there has been some uncertainty regarding the crystal structure or structures of the parent phase. Here we show that, under equilibrium conditions, the parent phase possesses the L2₁ structure between its A_p (about 79 °C) and ∼630 °C, and the B2 primitive cubic structure between ∼630 °C and its melting point. It melts directly from B2 into the liquid state and hence never achieves the random bcc A2 structure that has been previously mooted. Splat-cast samples of the alloy are martensitic, proving that development of equilibrium order and defect concentration are not pre-requisites for the A → M transformation to occur.     

The YbNi2−xSn compound, a new structure type of ternary stannides

The crystal structure of the new ternary stannide YbNi_2−xSn [space group P6₃/mmc (N 194), z=4] was investigated using single crystal X-ray diffraction data (automatic single crystal diffractometers Philips PW1100 and Bruker SMART CCD, Mo K radiation). Three crystals with different composition YbNi_1.695Sn [a=4.424(4) Å, c=15.232(6) Å, V=258.2(4) ų, ρ=10.066 g cm⁻³, μ=57.32 mm⁻¹], YbNi_1.705Sn [a=4.424(5) Å, c=15.179(7) Å, V=257.3(4) ų, ρ=10.116 g cm⁻³, μ=57.59 mm⁻¹] and YbNi_1.745Sn [a=4.303(6) Å, c=16.001(9) Å, V=256.7(5) ų, ρ=10.199 g cm⁻³, μ=58.00 mm⁻¹] were refined to R=0.0494, wR²=0.1330, to R=0.0782, wR²=0.1916 and to R=0.0643, wR²=0.1460, respectively. The compounds belongs to a new structure type of intermetallic compounds and are formed from two hypothetical structures YbNi_1.5Sn (space group P6₃/mmc, z=4) and YbNi₂Sn (space group P6₃/mmc, z=4) containing segments of the MnCu₂Al, ZrBeSi and ZrPt₂Al structures.     

Structure of the ternary phase Co3Al8Ga and formation of the gallium-containing decagonal phase d-Co(Al, Ga)3(m)

The structure of the ternary phase Co₃Al₈Ga, Pearson symbol oI96, space group Immm, a=12.0081(7) Å, b=7.5701(6) Å, c=15.394(1) Å is isotypic with Co₂NiAl₉. Powder diffraction data are reported for this ternary intermetallic compound. Using liquid quenching, the metastable pseudoternary decagonal phase d-Co(Al, Ga)₃(m) was obtained in the aluminium-rich portion of the ternary system Co–Al–Ga. Gallium substitutes for aluminium atoms in the d-Co(Al, Ga)₃(m) phase up to a mol fraction x_Ga=0.10. In the phase of the binary system Co–Al richest in aluminium, Co₂Al₉, the aluminium atomic positions can be occupied by gallium up to a gallium content of x_Ga=0.05.     

Synthesis and properties of Ba3NaRu2O9−δ and Ba3(Na, R)Ru2O9−δ (R=rare earth) crystals

Crystals of Ba₃NaRu₂O_9−δ (δ≈0.5) and Ba₃(Na, R)Ru₂O_9−δ (R=Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb) were grown by an electrochemical method, and their crystallographic, magnetic, and electric properties were studied. All crystals have a hexagonal structure of space group P6₃mmc. Ba₃NaRu₂O_9−δ and Ba₃(Na, R)Ru₂O_9−δ (except Ce) have a negative asymptotic Curie temperature suggesting the existence of an antiferromagnetic order; however, they are paramagnetic at temperatures above 1.7 K. Ba₃NaRu₂O_9−δ has an effective magnetic moment P_eff of 0.91 μ_B, while P_eff of Ba₃(Na, R)Ru₂O_9−δ (except Ce) reflects the large free-ion moment of the rare earth ions. Ba₃(Na, Ce)Ru₂O_9−δ shows peculiar magnetic behavior that differs from the magnetism of other Ba₃(Na, R)Ru₂O_9−δ crystals. The resistivity of all crystals exhibits an activation-type temperature dependence with an activation energy in the range of 0.10.2 eV.     

Physical properties of Mo6−xRuxTe8 and Mo6Te8−xSx

A series of the Chevrel phases, Mo_6−xRu_xTe₈ and Mo₆Te_8−xS_x (x=0, 1, 2), has been prepared and the various physical properties, such as the elastic modulus, Debye temperature, and electrical resistivity, have been evaluated. The relationships between several properties of the compounds have also been studied. Young’s modulus and Debye temperature of Mo_6−xRu_xTe₈ and Mo₆Te_8−xS_x increase with increasing x value. The relationship between the Vickers hardness and Young’s modulus shows ceramic characteristics for Mo_6−xRu_xTe₈, while they show glass-like characteristics for Mo₆Te_8−xS_x. The electrical resistivities of Mo_6−xRu_xTe₈ and Mo₆Te_8−xS_x increase with increasing x value.     

Crystal structure and magnetism of the Y2Pd14B5 compound

The crystal structure of the ternary boride Y₂Pd₁₄B₅, space group I4₁/amd, a=8.484(2) Å, c=16.490(3) Å, V=1186.98 ų, Z=4, was refined down to R=0.0475, wR2=0.1276 from single crystal X-ray diffraction data. Two types of coordination for boron atoms were observed: the coordination sphere for the B1 atom is a trigonal prism with one additional atom; the B2 atom has only four neighboring atoms which form a square. No boron–boron contact was observed. Analysis of the Y₂Pd₁₄B₅ crystal structure shows the existence of a correlation between this structure and the Sc₄Ni₂₉B₁₀ structure type. Magnetization and AC susceptibility measurements indicate that there is no superconducting or magnetic transition in Y₂Pd₁₄B₅ down to 2 K.     

Single crystal preparation and crystal structure of the Cu2Zn/Cd,Hg/SnSe4 compounds

Single crystals of Cu₂Zn/Cd/SnSe₄ were grown using a solution-fusion method. The crystal structure of the Cu₂Zn/Cd,Hg/SnSe₄ compounds were investigated using X-ray powder diffraction. These compounds crystallize in the stannite structure (space group I 2m) with the lattice parameters: a=0.56882(9), c=1.13378(9) nm, c/a=1.993 (Cu₂ZnSnSe₄), a=0.58337(2), c=1.14039(4) nm, c/a=1.955 (Cu₂CdSnSe₄) and a=0.58288(1), c=1.14179(2) nm, c/a=1.959 (Cu₂HgSnSe₄). Atomic parameters were refined in the isotropic approximation (R_I=0.0517, R_I=0.0511 and R_I=0.0695 for Cu₂ZnSnSe₄, Cu₂CdSnSe₄ and Cu₂HgSnSe₄, respectively).     

Crystallographic site of Mn in the icosahedral cluster of LaCo13−xMnx compounds

Studies on the structure and the crystallographic site of Mn in LaCo_13−xMn_x compounds were carried out by using X-ray diffraction and X-ray absorption fine structure (XAFS) of the Mn K-edge. These compounds with x≤3.0 adopt a NaZn₁₃-type structure consisting of icosahedral clusters. The lattice constant increases with the Mn concentration. The calculated XAFS curves of the center and the corner sites in the icosahedral clusters for the Mn K-edge are obtained by using the program . The fitting result for the corner site agrees much better with the observed XAFS spectrum than that for the center site. Therefore, the Mn site is determined to be the corner Co site in the icosahedral clusters of all the compounds. In comparison with the crystallographic parameters of LaCo₁₃, the icosahedral clusters composed of Mn atoms expand and the crystallographic Mn site is slightly more close to the La atom.