Space Group Pbam Research Articles

Influence of the Bi3+ electron lone pair in the evolution of the crystal and magnetic structure of La1−xBixMn2O5 oxides

La1−xBixMn2O5 (x = 0, 0.2, 0.4, 0.6, 0.8 and 1) oxides are members of the RMn2O5 family. The entire series has been prepared in polycrystalline form by a citrate technique. The evolution of their magnetic and crystallographic structures has been investigated by neutron powder diffraction (NPD) and magnetization measurements. All the samples crystallize in an orthorhombic structure with space group Pbam containing infinite chains of Mn4+O6 octahedra sharing edges, linked together by Mn3+O5 pyramids and (La/Bi)O8 units. These units become strongly distorted as the amount of Bi increases, due to the electron lone pair of Bi3+. All the members of the series are magnetically ordered below TN = 25–40 K and they present different magnetic structures. For the samples with low Bi content (x = 0.2 and 0.4) the magnetic structure is characterized by the propagation vector k = (0,0,1/2). The magnetic moments of the Mn4+ ions placed at octahedral sites are ordered according to the basis vectors (Gx, Ay, 0) whereas the Mn3+ moments, located at pyramidal sites, are ordered according to the basis vectors (0, 0, Cz). When the content of Bi increases, two different propagation vectors are needed to explain the magnetic structure: k1 = (0,0,1/2) and k2 = (1/2,0,1/2). For x = 0.6 and 0.8, k2 is predominant over k1 and for this propagation vector (k2) the magnetic arrangement is defined by the basis vectors (Gx, Ay,0) and (Fx, Cy, 0) for Mn4+ and Mn3+ ions, respectively.

Ethylenediamine as a bridging ligand: structure solution of two cadmium(II)-based coordination polymers from powder diffraction data

Structures of [Cd(C2H8N2)Cl2]n(1) and [Cd(C2H8N2)Br2]n(2) were solved from powder diffraction data. Compound (1) crystallizes in the space group Pbam (No. 55), a = 9.9021(7) Å, b = 7.8186(6) Å, c = 4.0705(3) Å, V = 315.13(3) Å3, Z = 2. (2) is isostructural: space group Pbam (No. 55), a = 10.405(2) Å, b = 7.8634(8) Å, c = 4.2079(5) Å, V = 344.28(6) Å3, Z = 2. The investigated compounds are examples of two-dimensional hybrid coordination polymers, in which neighboring metal centers are bridged via both organic and inorganic moieties: ethylenediamine molecules and halide anions. Both crystal structures were solved ab initio from powder data using direct methods.

Synthesis and crystal structure of a novel ludwigite borate: Mg2InBO5

A novel ludwigite borate Mg2InBO5 has been synthesized by solid-state reaction. Its crystal structure was solved by program Jana2006 from powder X-ray diffraction data, and then refined using Rietveld method. It crystallizes in the Pbam space group (No. 55) with a=12.54806(8)Å, b=9.46943(6)Å, c=3.13855(2)Å, V=372.932(4)Å3, and Z=4. The disorder of Mg and In atoms exists in Mg2InBO5. The In atoms prefer to occupy the M1 and M2 site, while Mg atoms tend to occupy the M3 and M4 sites, which is in agreement well with the cation distributions in the ludwigite family. The crystal structure of Mg2InBO5 is built from Mg/InO6 octahedra and trigonal BO3 groups stacking layer upon layer along the c-axis. The Mg/InO6 octahedra connect each other by sharing edges to form two flat walls along the c-axis in the sequence M3–M2–M3 and M1–M4–M1. The trigonal BO3 group in Mg2InBO5 was confirmed by infrared absorption spectrum, and UV–Vis diffuse reflectance spectrum of Mg2InBO5 has been measured. The structure characteristics of the ludwigite family were reviewed, with a possible rule proposed.

ChemInform Abstract: Temperature‐Dependent Structural Studies of Mullite‐Type Bi2Fe4O9.

AbstractThe thermal expansion of the title compound (space group Pbam) is investigated by single crystal neutron diffraction at 298 and 900 K and powder XRD over the range 298—1173 K.

Cuprous Halide Coordination Polymers Based on Cationic [Cu4X2] and [Cu3X] Clusters and [Cu2Br]n Layers with Tetrazolates as Assembling Ligands: Highly Connected Networks and Halide‐Dependent Luminescence

AbstractFive tetrazolate‐based coordination polymers with cationic copper(I) halide motifs, namely, Cu4(tta)2Cl2 (1, tta = tetrazolate), Cu4(tta)2Br2 (2), Cu2(tta)I (3), Cu3(mtta)2Cl (4, mtta = 5‐methyltetrazolate), and Cu2(tta)Br (5) were prepared by hydro(solvo)thermal reactions of CuX2 or CuX with tetrazolato ligands in the presence of HX. Compounds 1, 2, and 3 show eight‐connected square‐planar layered structures constructed with butterfly‐like [Cu4X2]2+ (X = Cl, Br, I) clusters and μ4‐tta groups. Isomorphs 1 and 2 crystallize in the orthorhombic space group Pbca, but 3 crystallizes in the orthorhombic space group Pbam, because each μ4‐tta group is coordinated to three butterfly‐like clusters rather than four in 1 and 2. To the best of our knowledge, 1, 2, and 3 represent the only 2D coordination polymers with eight‐connected square planar topology to date. Compound 4 is a [Cu3Cl]2+ cluster based on the undocumented ten‐connected ZrIn2 topological framework. Compound 5 has a 3D pillar layered framework constructed with [Cu2Br]nn+ cationic layers. Compounds 1, 2, 4, and 5 exhibit strong green‐blue emission in the solid state at room temperature, whereas cuprous iodide complex 3 shows strong red luminescence.

Crystal Structure and Chemical Composition of Ludwigite from Vranovac Ore Deposit (Boranja Mountain, Serbia)

Abstract:The crystal structure of ludwigite from Vranovac ore deposit (Boranja Mt., Serbia) was refined using the X‐ray powder diffraction (XRPD) Rietveld method in the space group Pbam to a final RB=7.45% and RF=5.26%. It has the unit cell dimensions of: a= 9.2515(2) Å; b= 12.3109(2) Å; c= 3.03712 (7) Å; and V= 345.91(1) Å3. The calculated distances and angles are mostly in good agreement with the Mg2+‐Fe2+ substitutions across the M(1) and M(3) sites, as well as with the Fe3+‐Al3+ replacement in the M(4) site. However, the mean observed M(2)‐O distance is considerably shorter than prescribed, due to a slight increase of the Fe3+ content in the M(2) site. Such replacement was compensated by slight increase of the Fe2+ content in the M(4) site, resulting in the (Mg1.48Fe2+0.46Fe3+0.05Mn0.02)2.01 (Fe3+0.94Fe2+0.04Al0.02)1.00B1.00O5 composition. The formation temperature was estimated to be about 500–600°C. The influences of the various chemical compositions to the crystallographic parameters, M‐O distances, M(3) and M(4) sites shift, distortion parameters and estimated valences, were also studied and compared with other reference samples.

Crystallography, magnetic, and magnetocaloric properties of Gd57.5Co20Al22.5 alloy

To understand the structure and magnetocaloric effect (MCE) of the crystallized Gd-Co-Al bulk metallic glasses, investigations were performed on the unknown phase of the crystallization product. As a result, the new ternary phases with composition of Gd57.5Co20Al22.5 have been found in the Gd-Co-Al alloy system. The as-cast alloy adopts the orthorhombic crystal system with the space group of Pbam. The alloy preserves the single phase structure during annealing but experiences structural phase transition to crystallize in a different structure. The as-cast alloy orders antiferromagnetically at 59 K and continuous field-induced metamagnetic transition can be observed. The annealed one orders ferromagnetically at 101 K. The magnetization measurements suggest that the antiferromagnetic and ferromagnetic interactions coexist in both the as-cast and the annealed samples and they have complex magnetic structure. MCE of the two samples are far lower than that of the Gd-Co-Al bulk metallic glasses.

Thermochemistry of Sr2Ce1–xPrxO4 (x = 0, 0.2, 0.5, 0.8, and 1): Variable-Temperature and -Atmosphere in-situ and ex-situ Powder X-ray Diffraction Studies and Their Physical Properties

A novel family of metal oxides with a chemical formula of Sr(2)Ce(1-x)Pr(x)O(4) (x = 0, 0.2, 0.5, 0.8, and 1) was developed as mixed oxide ion and electronic conductors for solid oxide fuel cells (SOFCs). All of the investigated samples were synthesized by the ceramic method at 1000 °C in air and characterized by powder X-ray diffraction (PXRD), selected area electron diffraction (SAED), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and electrochemical impedance spectroscopy (EIS). Ex-situ PXRD reveals that the Sr(2)PbO(4)-type Sr(2)CeO(4) decomposes readily into a mixture of perovskite-type SrCeO(3) and rock-salt-type SrO at 1400 °C in air. Surprisingly, the decomposed products are converted back to the original Sr(2)PbO(4)-type Sr(2)CeO(4) phase at 800 °C in air, as confirmed by in-situ PXRD. Thermal decomposition is highly suppressed in Sr(2)Ce(1-x)Pr(x)O(4) compounds for Pr > 0, suggesting that Pr improves the thermal stability of the compounds. Rietveld analysis of PXRD and SAED supported that both Pr and Ce ions are located on the 2a site in Pbam (space group no. 55). The electrical transport mechanism could be correlated to the reduction of Pr and/or Ce ions and subsequent loss of oxide ions at elevated temperatures, as shown by TGA and in-situ PXRD. Conductivity increases with Pr content in Sr(2)Ce(1-x)Pr(x)O(4). The highest total conductivity of 1.24 × 10(-1) S cm(-1) was observed for Sr(2)Ce(0.2)Pr(0.8)O(4) at 663 °C in air.

On the Nature of Ge–Pb Bonding in the Solid State. Synthesis, Structural Characterization, and Electronic Structures of Two Unprecedented Germanide-Plumbides

Reported are the syntheses and the crystallographic characterization of two structurally related solid-state compounds: (Eu(1-x)Ca(x))(2)Ge(2)Pb (space group Pbam) and (Sr(x)Eu(1-x))(2)Ge(2)Pb (space group Cmmm). Both structures boast anionic sublattices with fully ordered Ge and Pb at the atomic level, which is unusual for elements of the same group. Despite the nearly identical formulas and the similar chemical makeup, the nature of the chemical bonding in the two compounds is subtly different; in the (Eu(1-x)Ca(x))(2)Ge(2)Pb structure, Ge and Pb are positioned at a relatively shorter distance from one another (<3.0 Å). The close proximity of the atoms leads to interactions, which are seen for the first time in an extended structure and can be suggested to have a covalent character. This conjecture is supported by extensive electronic band-structure calculations using first principles. Magnetic susceptibility measurements reveal Eu(2+) ground state ([Xe]4f(7) configuration) and the presence of an antiferromagnetic ordering at cryogenic temperatures.

Mixed valence of iron inside tetrahedral and pseudopyramids in BiFe2O5−δ

An oxide of stoichiometry BiFe${}_{2}$O${}_{5\ensuremath{-}\ensuremath{\delta}}$ has been prepared by thermal treatments under high oxygen pressure. The crystallographic structure has been determined by neutron powder diffraction (NPD); it is defined in an orthorhombic structure (space group Pbam) with the Fe cations in octahedral and tetrahedral sites, similar to the previously reported BiFe${}_{2}$O${}_{4.5}$. Nevertheless, by Fourier synthesis a non-negligible occupancy of oxygen anions in interstitial positions has been determined, corresponding to a final stoichiometry BiFe${}_{2}$O${}_{4.63(1)}$. It implies that some tetrahedral Fe environments are transformed into pseudo pyramids and thus, some Fe cations are oxidized to a 4+ oxidation state. We have confirmed the mixed valence of Fe by M\ossbauer and x-ray-absorption spectroscopy obtaining \ensuremath{\sim}Fe${}^{3.2+}$ by both techniques. In addition, the magnetic structure below the magnetic ordering transition, around ${T}_{N}$ $=$ 250 K, has also been determined by NPD. It is antiferromagnetic with a propagation vector of k $=$ (1/2,1/2,1/2) and ordered magnetic moments of 4.6(1) ${\ensuremath{\mu}}_{\mathrm{B}}$ at Fe in octahedral positions and 3.7(1) ${\ensuremath{\mu}}_{\mathrm{B}}$ at Fe in pyramidal/tetrahedral positions.

A5Sn2As6 (A = Sr, Eu). Synthesis, Crystal and Electronic Structure, and Thermoelectric Properties

Two new ternary Zintl phases, Sr(5)Sn(2)As(6) and Eu(5)Sn(2)As(6), have been synthesized, and their structures have been accurately determined through single-crystal X-ray diffraction. Both compounds crystallize in orthorhombic space group Pbam (No. 55, Z = 2) with cell parameters of a = 12.482(3)/12.281(5) Å, b = 14.137(3)/13.941(5) Å, and c = 4.2440(10)/4.2029(16) Å for Sr(5)Sn(2)As(6) (R1 = 0.0341; wR2 = 0.0628) and Eu(5)Sn(2)As(6) (R1 = 0.0324; wR2 = 0.0766), respectively. Their structure belongs to the Sr(5)Sn(2)P(6) type, which can be closely related to the Ca(5)Ga(2)As(6) type. Electronic band structure calculations based on the density functional theory reveal an interesting electronic effect in the structure formation of these two types of Zintl phases, which substantially affect their corresponding electronic band structure. Related studies on the thermal stability, magnetism, and thermoelectric properties of Eu(5)Sn(2)As(6) are presented as well.

The complex metal-rich boride Ti1+xRh2−x+yIr3−yB3 (x=0.68, y=1.06) with a new structure type containing B4 zigzag fragments: Synthesis, crystal chemistry and theoretical calculations

Polycrystalline samples and single crystals of the new complex boride Ti1+xRh2−x+yIr3−yB3 (x=0.68; y=1.06) were synthesized by arc-melting the elements in a water-cooled copper crucible under an argon atmosphere and characterized by X-Ray diffraction as well as EDX measurements. The crystal structure was refined on the basis of single crystal data. The new phase, which represents a new structure type containing trans zigzag B4 fragments as well as isolated boron atoms crystallizes in the orthorhombic space group Pbam (Nr. 55) with the lattice parameters a=8.620(1)Å, b=14.995(2)Å and c=3.234(1)Å. First-principles density functional theory calculations using the Vienna ab-initio simulation package (VASP) were performed on an appropriate structural model (using a supercell approach) and the experimental crystallographic data could be reproduced accurately. Based on this model, the density of states and crystal orbital Hamilton population (for bonding analysis) were calculated, using the linear muffin-tin orbital atomic sphere approximation (LMTO-ASA) method. According to these calculations, this metal-rich compound should be metallic, as expected. Furthermore, very strong boron–boron interactions are observed in the trans zigzag B4 fragment, which induce a clear differentiation of two types of metal–boron contacts with different strength. The observed three-dimensional metal–metal interaction is in good agreement with the predicted metallic behavior.

Crystal chemistry and properties of mullite-type Bi2 M 4O9: An overview

Abstract Bi2 M 4O9 (M = Al3+, Ga3+, Fe3+) belongs to the family of mullite-type crystal structures. The phases are orthorhombic with the space group Pbam. The backbones of the isostructural phases are edge-connected, mullite-type octahedral chains. The octahedral chains are linked by dimers of M 2O7 tetrahedral groups and by BiO polyhedra. The Bi3+ cations in Bi2 M 4O9 contain stereo-chemically active 6s2 lone electron pairs (LEPs) which are essential for the stabilization of the structure. Although the octahedral chains of the closely related Bi2Mn4O10 are similar to those of Bi2 M 4O9, Bi2Mn4O10 contains dimers of edge-connected, five-fold coordinated pyramids instead of four-fold coordinated tetrahedra. Also the 6s2 LEPs of Bi3+ in Bi2Mn4O10 are not stereo-chemically active. Complete and continuous solid solutions exist for Bi2(Al1 – x Fe x )4O9 and Bi2(Ga1 – x Fe x )4O9 (x = 0–1). Things are more complex in the case of the Bi2(Fe1 – x Mn x )4O9+ y mixed crystals, where a miscibility gap occurs between x = 0.25–0.75. In the Fe-rich mixed crystals most Mn atoms enter the octahedra as Mn4+, with part of the tetrahedral dimers being replaced by fivefold coordinated polyhedra, whereas in the Mn-rich compound Fe3+ favorably replaces Mn3+ in the pyramids. The crystal structure of Bi2 M 4O9 directly controls its mechanical properties. The stiffnesses of phases are highest parallel to the strongly bonded octahedral chains running parallel to the crystallographic c -axis. Perpendicular to the octahedral chains little anisotropy is observed. The temperature-induced expansion perpendicular to the octahedral chains is probably superimposed by contractions. As a result the c -axis expansion appears as relatively high and does not display its lowest value parallel to c , as could be inferred. Maximally 6% of Bi3+ is substituted by Sr2+ in Bi2Al4O9 corresponding to a composition of (Bi0.94Sr0.06)2Al4O8.94. Sr2+ for Bi3+ substitution is probably associated with formation of vacancies of oxygen atoms bridging the tetrahedral dimers. Hopping of oxygen atoms towards the vacancies should strongly enhance the oxygen conductivity. Actually the conductivity is rather low (σ = 7 · 10− 2 S m− 1 at 1073 K, 800°C). An explanation could be the low thermal stability of Sr-doped Bi2Al4O9, especially in coexistence with liquid Bi2O3. Therefore, Bi2Al4O9 single crystals and polycrystalline ceramics both with significant amounts of M 2+ doping (M = Ca2+, Sr2+) have not been produced yet. Thus the question whether or not M 2+-doped Bi2 M 4O9 is an oxygen conducting material is still open.

On the structural relations of malachite. I. The rosasite and ludwigite structure families

The crystal structures of malachite Cu(2)(OH)(2)CO(3) and rosasite (Cu,Zn)(2)(OH)(2)CO(3), though not isotypic, are closely related. A previously proposed approach explaining this relation via a common hypothetical parent structure is elaborated upon on the basis of group-subgroup considerations, leading to the conclusion that the aristotype of malachite and rosasite should crystallize in the space group Pbam (No. 55). An ICSD database search for actual representatives of this aristotype leads to the interesting observation that the structure type of ludwigite (Mg,Fe)(2)FeO(2)BO(3), which is adopted by several natural and synthetic oxide orthoborates M(3)O(2)BO(3), is closely related to the proposed malachite-rosasite aristotype and thus to the malachite-rosasite family of hydroxide carbonates M(2)(OH)(2)CO(3) in general. Relations within both structure families and their analogies are summarized in a joint simplified Bärnighausen tree.

Structural, electronic and magnetic properties of layered REB2C compounds (RE=Dy, Tm, Lu)

The crystal structure of LuB2C has been determined from single crystal and powder X-ray diffraction data. It crystallizes in the orthorhombic space group Pbam (a=6.7429(1)Å, b=6.7341(1)Å, c=3.5890(1)Å, Z=4, R1=0.024 (wR2=0.059) for 436 reflections with Io>2σ(Io)). The compounds REB2C (RE=Y, Tb–Lu) are isotypic. The boron and carbon atoms form infinite, planar two-dimensional nets which alternate with sheets of rare-earth metal atoms. Inside the nonmetal atom nets, a coloring with fused B2C2 rhombuses and B5C2 heptagons is proposed, supported by NMR experiments and density functional theory calculations. The calculated density of states of LuB2C indicates this compound to be metallic. The magnetic properties of the isotypic compound TmB2C, has been measured in the temperature range 2K<T<300K and in various external fields up to B=7T. The sample undergoes an antiferromagnetic (AFM) transition at TN=12K, and at fields B>3T a metamagnetic transition is encountered. The temperature dependence of the electrical resistivity proves the metallic character of the TmB2C compound as well as the AFM ordering.

Orthorombic La2Ni2In form – A new intergrowth CsCl – and AlB2 – type slabs

The crystal structure of a new orthorhombic modification of o-La2Ni2In (space group Pbam, Pearson code oP20, a = 7.5840(9), b = 15.4891(13), c = 3.9154(4) Å, Z = 4) has been investigated by X-ray single crystal methods. The structure is closely related to the tetragonal La2Ni2In form (Mo2FeB2 type, space group P4/mbm). Both La2Ni2In forms together with the structure types Mn2AlB2, Cr3AlB4, Lu5Ni2In4 and Nd11Pd4In9 form a homologous series, which is described by the general formula Rm+nT2nXm, where m and n are the number of CsCl and AlB2 related slabs per unit cell. In o-La2Ni2In the CsCl and AlB2 slabs are intergrown in a 4:4 ratio in a new mode. The coordination polyhedra of the lanthanum atoms are pentagonal prisms with seven additional atoms, the indium atom is surrounded tetrahexahedrally and the nickel atoms are in the center of tri-caped trigonal prisms.

Crystal structures and hardness of novel compounds: Hexagonal Mo(CuxAl1−x)6Al4, MoCu2Al8−x and orthorhombic {Mo,W,Re}Ni2−xAl8+x

The crystal structures of a series of compounds have been solved from X-ray single crystal diffractometry: Mo(CuxAl1−x)6Al4 (x = 0.416), MoNi2−xAl8+x (x = 0.165), WNi2−x−y□yAl8+x−z□z, (x = 0.162, y = 0.015, z = 0.010) and ReNi2Al8−x (x = 0.033). Mo(CuxAl1−x)6Al4 crystallizes with hexagonal symmetry and lattice parameters, a = 0.50030(1) and c = 0.76279(3) nm; space group P6/mmm, No. 191, as an unfilled structure variant of the MgFe6Ge6-type with a vacant 2c site. This structure is made up of alternate blocks of (unfilled) CaCu5 and Zr4Al3 in a ratio of 1:1. A superstructure of this compound (a = a0√3, c = 2c0) was solved with a Rietveld refinement of X-ray powder diffraction data as a fully ordered structure with formula MoCu2Al8−x. It adopts space group P6, No. 168 with lattice parameters a = 0.86769(1), c = 1.52149(2) nm. A Bärnighausen tree was derived reflecting the close relation among these two structure types. The compounds {Mo,W,Re}Ni2−xAl8+x crystallize in a novel structure type (ReNi2Al8−x–type; space group Pbam, No. 55). Whereas ReNi2Al8−x is a fully ordered structure with some defects in the two 4g sites occupied by Al, Ni + Al atoms randomly share one crystallographic site in isotypic {Mo,W}Ni2−xAl8+x, which causes splitting of three neighboring Al-sites. Lattice parameters and residual values of the refinements were: a = 1.00320(2), b = 1.51258(3), c = 0.83890(2) nm; RF2 = 0.017 for the Re-compound, a = 1.00664(2), b = 1.53108(2), c = 0.85205(2) nm, RF2 = 0.035 for the Mo-compound and a = 1.00683(2), b = 1.53236(3), c = 0.85232(2) nm; RF2 = 0.024 for the W-compound. As the ReNi2Al8−x-type structure is another superstructure of the hexagonal Mo(CuxAl1−x)6Al4 type, a Bärnighausen tree was derived, which documents the close relation among these two structure types. Phase equilibria in the Al-rich corner of W–Ni–Al at 930 °C is also reported showing the presence of a WNi2Al8 phase. Precise atom positions have been derived from X-ray single crystal data for binary Ni2Al3 confirming the space group P3¯m1 (No. 164). Atom positions and lattice parameters (a = 0.40533(2), c = 0.49038(3) nm) are very close to the parameters hitherto reported in the literature from X-ray powder diffraction data. Vicker’s hardness was measured for all isotypic compounds {Mo,W,Re}Ni2Al8−x revealing a hardness of HV = 965 ± 25 MPa for the Re-containing material, which is higher by about 100 MPa in comparison to the Mo and W containing phases.

Mixed crystal formation and structural studies in the mullite-type system Bi2Fe4O9–Bi2Mn4O10

The limits of metal cation substitution and distribution in the sequence Bi2Fe4O9–Bi2Mn4O10 have been investigated by solid state synthesis, X-ray powder diffraction, and Mössbauer spectroscopy. Rietveld refinements conducted for the entire range along the join indicate the structures are orthorhombic with space group Pbam, with partial transition-metal site disorder confirmed and detailed by Mössbauer spectroscopy. Single-phase regions are found near each end-member and a two-phase region is observed at intermediate compositions, extending from about x=1 to 3, according to the general formula of the mixed crystals Bi2Fe4−xMnxO10−δ. An incorporation of Mn at octahedral sites replacing Fe is taken into account for the Bi2Fe4O9-related side of the system. Charge compensation is believed to be effected by addition of O, which gives rise to the formation of FeO5 pyramids. At the Bi2Mn4O10-related side of the system, substitution of pyramidal Mn3+ by Fe3+ is envisaged.

Crystal and magnetic properties of Er 5Ni 2In 4 at low temperatures

The Er 5Ni 2In 4 compound belongs to a novel family of rare earth-based intermetallics crystallizing within the Lu 5Ni 2In 4-type structure ( Pbam Space group). In this paper we report results of structural as well as magnetic studies including X-ray diffraction (between 12 and 300 K); neutron diffraction (between 1.5 and 24 K), magnetometric and calorimetric data (in 2–300 K temperature range). The Er 3+ ions occupy three crystal positions within the unit cell: two 4g sites and the 2a site. According to results of neutron diffraction, the Er magnetic moments at 4g sites form a non-collinear magnetic structure below 18.5 K. Additional magnetic transition at about 2 K, originating in ordering of the 2a sublattice, occurs as well. In addition, magnetic entropy derived on the basis of specific heat studies is discussed yielding the doublet crystal field ground states for each of the sublattices.

The new high-pressure borate Co7B24O42(OH)2·2 H2O—Formation of edge-sharing BO4 tetrahedra in a hydrated borate

The new borate hydrate Co7B24O42(OH)2·2H2O was synthesized under high-pressure/high-temperature conditions of 6GPa and 880°C in a Walker-type multianvil apparatus. The compound crystallizes in the orthorhombic space group Pbam (Z=2) with the lattice parameters a=819.0(2), b=2016.9(4), c=769.9(2)pm, V=1.2717(4)nm3, R1=0.0758, wR2=0.0836 (all data). The new structure type of Co7B24O42(OH)2·2H2O is built up from corner-sharing BO4 tetrahedra forming corrugated layers, that are interconnected among each other by two edge-sharing BO4 tetrahedra (B2O6 units) forming Z-shaped channels. Interestingly, the here presented structure of Co7B24O42(OH)2·2H2O is closely related to the structures of M6B22O39·H2O (M=Fe, Co), which exhibit BO4 tetrahedra in an intermediate state on the way to edge-sharing BO4 tetrahedra.