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At least 1,423 records · Page 79
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DOE OSTI2012

New rare-earth metal germanides with bismuth substitution. Synthesis, structural variations, and magnetism of the RE[Bi{sub x}Ge{sub 1-x}]{sub 2} (RE=Y, Pr, Nd, Sm, Gd-Tm, Lu) compounds

Single-crystals of the novel rare-earth metal-bismuth digermanides with idealized formula RE[Bi{sub x}Ge{sub 1-x}]{sub 2} (RE=Y, Pr, Nd, Sm, Gd-Tm, Lu; x<0.16(1)) have been obtained using the Bi-flux technique. Their structures have been established by single-crystal X-ray diffraction; they can be divided into three classes, closely related to the ZrSi{sub 2} structure with the space group Cmcm (no. 63). The structural relationship and the variations with the type of the rare-earth metal have been explored and discussed. Temperature-dependent magnetization measurements on the single-crystals reveal magnetic behavior, which have been rationalized based on the mean-field theory. At cryogenic temperatures, the localized 4f electrons in most of the compounds exhibit antiferromagnetic ordering, mediated by the conduction electrons via Ruderman-Kittel-Kasuya-Yosida (RKKY) exchange interactions. - Graphical abstract: This paper details the synthesis and the structural characterization of an extended series of rare-earth metal-bismuth-germanides RE[Bi{sub x}Ge{sub 1-x}]{sub 2} (RE=Y, Pr-Sm, Gd-Tm, Lu). They crystallize with the same extended symmetry (space group Cmcm), but with three distinct structures, which are closely related. Magnetization measurements show low-temperature antiferromagnetic ordering. RE[Bi{sub x}Ge{sub 1-x}]{sub 2} are the first compounds between these elements. Highlights: Black-Right-Pointing-Pointer RE[Bi{sub x}Ge{sub 1-x}]{sub 2} (RE=rare-earth metal) are the first compounds of the respective elements. Black-Right-Pointing-Pointer Their structures are closely related. Black-Right-Pointing-Pointer Three structures can be distinguished based on the packing of the REGe{sub 6} triangular prisms. Black-Right-Pointing-Pointer All compounds show low-temperature antiferromagnetic ordering.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Physical properties of double perovskite-type barium neodymium osmate Ba{sub 2}NdOsO{sub 6}

The crystal, magnetic structures and physical properties of the double perovskite-type barium neodymium osmate Ba{sub 2}NdOsO{sub 6} are investigated through powder X-ray and neutron diffraction, electrical conductivity, magnetic susceptibility, and specific heat measurements. The Rietveld analysis reveals that the Nd and Os ions are arranged with regularity over the six-coordinate B sites in a distorted perovskite ABO{sub 3} framework. The monoclinic crystal structure described by space group P2{sub 1}/n (tilt system a{sup -}a{sup -}c{sup +}) becomes more distorted with decreasing temperature from 300 K down to 2.5 K. This compound shows a long-range antiferromagnetic ordering of Os{sup 5+} below 65 K. An antiferromagnetic ordering of Nd{sup 3+} also occurs at lower temperatures ({approx}20 K). The magnetic structure is of Type I and the magnetic moments of Nd{sup 3+} and Os{sup 5+} ions are in the same direction in the ab-plane. - Graphical Abstract: The Magnetic structure of Ba{sub 2}NdOsO{sub 6} is of Type I, and the magnetic moments of the Nd{sup 3+} and Os{sup 5+} ions are in the same direction in the ab-plane. Highlights: Black-Right-Pointing-Pointer Crystal structures of Ba{sub 2}NdOsO{sub 6} are determined to be monoclinic below 300 K. Black-Right-Pointing-Pointer Its electrical resistivity shows a Mott variable-range hopping behavior with localized carriers. Black-Right-Pointing-Pointer An antiferromagnetic ordering of the Os{sup 5+}moment occurs at 65 K. Black-Right-Pointing-Pointer The magnetic structure of Ba{sub 2}NdOsO{sub 6} is determined to be of Type I.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Effects of competing magnetic interactions on the electronic transport properties of CuCrSe{sub 2}

We have synthesized single-phase samples of the CuCrSe{sub 2} phase that exhibits hexagonal-rhombohedral layered crystal structure with space group R3m. Here we present a detailed study of electronic transport and magnetic properties of CuCrSe{sub 2}. We moreover investigate the heat capacity of CuCrSe{sub 2} in comparison to that of CuCrS{sub 2}. The electrical resistivity of CuCrSe{sub 2} shows metallic-like behavior down to 2 K, while the thermoelectric power is large around 100 {mu}V K{sup -1} at 300 K. A weak anomaly in resistivity and a rounded maximum in magnetic susceptibility are observed around 55 K. No sharp transition at 55 K is observed in the heat capacity of CuCrSe{sub 2}, rather a visible maximum is seen. At low temperatures from 2 to 14 K, the magnetic heat capacity follows T{sup 2}-dependence. We tentatively believe this behavior of CuCrSe{sub 2} to be due to competing magnetic interactions between intralayer Cr atoms. The ferromagnetic Cr-Se-Cr indirect exchange among intralayer Cr atoms is enhanced in the selenide compound (that is more metallic than the sulfide compound), and competes with the antiferromagnetic Cr-Cr direct interactions. The interlayer antiferromagnetic exchange through Cu atoms leads to magnetic ordering at low temperature at T{sub N}=55 K. - Graphical abstract: Comparison of magnetic properties of CuCrSe{sub 2} and CuCrS{sub 2} indicates a sharp cusp-like anomaly in magnetic susceptibility at the antiferromagnetic transition of CuCrS{sub 2} while the maximum of CuCrSe{sub 2} is well rounded. Magnetization is reversible after field-cooling (FC) and zero-field-cooling (ZFC) for both compounds. Highlights: Black-Right-Pointing-Pointer Layered CuCrSe{sub 2} can be synthesized in both fully and partially cation-ordered forms. Black-Right-Pointing-Pointer Contrary to previously believed insulating nature the cation-ordered phase is metallic. Black-Right-Pointing-Pointer Magnetic property of CuCrSe{sub 2} is somewhat different from that of CuCrS{sub 2}. Black-Right-Pointing-Pointer Magnetization and heat capacity data suggest complex short-range ordering for CuCrSe{sub 2}.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Six novel transition-metal phosphite compounds, with structure related to yavapaiite: Crystal structures and magnetic and thermal properties of A{sup I}[M{sup III}(HPO{sub 3}){sub 2}] (A=K, NH{sub 4}, Rb and M=V, Fe)

Six new transition metal(III) phosphites A{sup I}[V{sup III}(HPO{sub 3}){sub 2}], where A=K (1), NH{sub 4} (2) and Rb (3) and A{sup I}[Fe{sup III}(HPO{sub 3}){sub 2}] where A=K (4), NH{sub 4} (5) and Rb (6) have been synthesized under hydrothermal conditions and the solid-state structures were solved from single-crystal X-ray diffraction data. These compounds crystallize in the hexagonal system, space group P6{sub 3}mc (no. 186), with a=5.3294(2) A and c=12.3130(5) A for 1, a=5.3330(2) A and c=12.8760(4) A for 2, a=5.3459(2) A and c=12.6850(8) A for 3, a=5.3256(1) A and c=12.2362(3) A for 4, a=5.3229(2) A and c=12.8562(4) A for 5, a=5.3393(2) A and c=12.6913(5) A for 6, with Z=2 in the six phases. The crystal structures of these compounds are isotypic and exhibit a layered structure stacked along the c-axis with the A{sup +} cations located in the interlayer space. The [M{sup III}(HPO{sub 3}){sub 2}]{sup -} sheets are formed by MO{sub 6} octahedra interconnected by HPO{sub 3} tetrahedral phosphite oxoanions through sharing vertices. Thermal analysis shows a large range of stability for compounds containing potassium and rubidium cations with decomposition starting around 550 K for stable compounds and above 840 K for the most stable compounds leading in general to pyrophosphate compounds. Triangular nets of metallic centers are observed within the layers in which antiferromagnetic interactions are evidenced by magnetic susceptibility measurements suggesting magnetic frustration. - Graphical abstract: Six new transition metal(III) phosphites A{sup I}[M{sup III}(HPO{sub 3}){sub 2}], where A=K, NH{sub 4}, Rb and M=V, Fe, have been synthesized. The crystal structures of these compounds are isotypic and exhibit a lamellar structure related to Yavapaiite. The M(HPO{sub 3}){sub 2} layers separated by cationic species present the metallic centers in a triangular arrangement. Bulk antiferromagnetic behavior is observed for all the studied compounds. Highlights: Black-Right-Pointing-Pointer A new family of transition metal phosphites has been prepared. Black-Right-Pointing-Pointer The structure of these compounds is related to layered minerals like Yavapaiite. Black-Right-Pointing-Pointer Antiferromagnetic coupling is evidenced suggesting possible magnetic frustration. Black-Right-Pointing-Pointer Thermal studies show, in general, oxidation of phosphites into pyrophosphates.

36 MATERIALS SCIENCE↗
DOE OSTI2013

The dimeric [V{sub 2}O{sub 2}F{sub 8}]{sup 4−} anion: Structural characterization of a magnetic basic-building-unit

New materials built from the [V{sub 2}O{sub 2}F{sub 8}]{sup 4−} anionic basic-building-unit (BBU) exhibit interesting magnetic properties owing to the proximity of the two d{sup 1} V(IV) cations and the orbital interactions of fluoride and oxide ligands. In our search to target such materials, the vanadium oxide–fluoride compound [dpaH{sub 2}]{sub 2}[V{sub 2}O{sub 2}F{sub 8}] in which a dimeric anion [V{sub 2}O{sub 2}F{sub 8}]{sup 4−} is isolated in a hydrogen bond network was hydrothermally synthesized (dpa=2,2′-dipyridylamine). This hydrogen bond network is able to stabilize the highly ionic species [V{sub 2}O{sub 2}F{sub 8}]{sup 4−} as demonstrated with bond valence calculations. The coordination of the O{sup 2−}/F{sup −} ordered ligands was investigated and antiferromagnetic coupling of the isolated BBU was measured. - The new hybrid compound [dpaH{sub 2}]{sub 2}[V{sub 2}O{sub 2}F{sub 8}] built from the interesting [V{sub 2}O{sub 2}F{sub 8}]{sup 4−} magnetic basic-building-unit (BBU) was synthesized by the hydrothermal method. The coordination of the O{sup 2−}/F{sup −} ordered ligands was investigated by BVS calculations and antiferromagnetic coupling was measured. Highlights: ► A new vanadium oxyfluoride was synthesized by hydrothermal method. ► The Dimeric [V{sub 2}O{sub 2}F{sub 8}]{sup 4−} basic building unit is isolated in the hydrogen bond networks. ► The coordination of [V{sub 2}O{sub 2}F{sub 8}]{sup 4−} units to the extended structure is investigated. ► Isolated [V{sub 2}O{sub 2}F{sub 8}]{sup 4−} units exhibit antiferromagnetic coupling.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Boric acid flux synthesis, structure and magnetic property of MB₁₂O₁₄(OH)₁₀ (M=Mn, Fe, Zn)

Three new borates MB₁₂O₁₄(OH)₁₀ (M=Mn, Fe, Zn) have been synthesized by boric acid flux methods, which are isotypic to NiB₁₂O₁₄(OH)₁₀. Single-crystal XRD was performed to determine the crystal structures in detail. They all crystallize in the monoclinic space group P2₁/c. The size of MO{sub 6} (M=Mg, Mn, Fe, Co, Ni, Zn) octahedron shows a good agreement with the Shannon effective ionic radii of M²⁺. Magnetic measurements indicate MnB₁₂O₁₄(OH)₁₀ is antiferromagnetic without a long-range ordering down to 2 K. The values of its magnetic superexchange constants were evaluated by DFT calculations, which explain the observed magnetic behavior. The UV–vis diffuse reflectance spectrum of ZnB₁₂O₁₄(OH)₁₀ suggests a band gap ~4.6 eV. DFT calculations indicate it has a direct band gap 4.9 eV. The optical band gap is contributed by charge transfers from the occupied O 2p to the unoccupied Zn 4s states. - Graphical abstract: Experimental and theoretical studies indicate MnB₁₂O₁₄(OH)₁₀ is antiferromagnetic without a long-range ordering. DFT calculations show ZnB₁₂O₁₄(OH)₁₀ has a direct band gap of 4.9 eV. Highlights: • MB₁₂O₁₄(OH)₁₀ (M=Mn, Fe, Zn) are synthesized by two-step boric acid flux method. • Single-crystal XRD was performed to determine the crystal structures in detail. • Size of MO₆ (M=Mg, Mn, Fe, Co, Ni, Zn) agrees with the effective ionic radii. • MnB₁₂O₁₄(OH)₁₀ is antiferromagnetic without a long-range ordering down to 2 K. • DFT calculations indicate ZnB₁₂O₁₄(OH)₁₀ has a direct band gap 4.9 eV.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Synthesis, crystal structure, and magnetic properties of bis(aqua)[μ-(terepthalato-κo,κo´)]copper(II)monohydrate [Cu(C₈O₄)(OH₂)₂]·H₂O

A novel one dimensional Cu(II) coordination polymer [Cu(C₈O₄)(OH₂)₂] ·H₂O 1 has been synthesized and characterized by elemental analysis, IR spectroscopy, X-ray crystal diffraction and magnetic measurements. Single-crystal structural analysis shows that complex 1 consist of 1D Cu(II) chain containing threefold bridging ligands, one (syn–syn) carboxylate and two water molecules. The magnetic study of 1 has been investigated, indicating an overall antiferromagnetic interaction in the complex. - Graphical abstract: The complex [Cu(C₈O₄)(OH₂)₂] ·H₂O was prepared by the reaction of solid copper(II)basic carbonate with an aqueous solution of sodium terephthalate under heating at 50–60 {sup o}C after which it was allowed to crystallize at room temperature. The structure of the complex is distorted octahedral. Magnetic study of the complex reveals antiferromagnetic behaviour. Highlights: • A novel copper(II) coordination polymer with terepthalate dianion was grown in an aqueous solution. • The single crystal growth temperature was 25 °C for period of two weeks. • The magnetic property of the complex was studied using SQUID. • The complex showed antiferromagnetic properties.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

From spin induced ferroelectricity to spin and dipolar glass in a triangular lattice: The CuCr{sub 1−x}V{sub x}O{sub 2} (0≤x≤0.5) delafossite

The change from antiferromagnetism induced ferroelectricity to spin glass ferroelectric relaxor has been studied along the CuCr{sub 1−x}V{sub x}O{sub 2} (0≤x≤0.5) solid solution of polycrystalline samples. As x increases from CuCrO{sub 2} (x=0) to CuCr{sub 0.82}V{sub 0.18}O{sub 2}, it is found that the Néel temperature decreases from ∼24 K down to ∼13 K. This progressive weakening of the antiferromagnetism of CuCrO{sub 2} induces a rapid decrease of the spin induced ferroelectricity with polarization values going from ∼44 μC/m{sup 2} down to ∼1.5 μC/m{sup 2} for x=0.04 and x=0.08, respectively. Beyond x=0.18 (0.20≤x≤0.50), ac-magnetic susceptibility and magnetization measurements evidence a spin glass state while dielectric permittivity and polarization measurements point towards a relaxor behaviour. This shows that competing magnetic interactions in delafossites are an efficient way to transform a spin induced magnetoelectric into a multiglass (spin and dipolar) state. - Graphical abstract: The P(T) curves evidencing the aging effect on polarization in CuCr{sub 0.5}V{sub 0.5}O{sub 2}: E=135 kV/m is applied during cooling at different temperatures. The P values and the inflection point of the transition depend on the poling temperature suggesting a relaxor behaviour. This effect related to the spin glass state is not observed for the lowest vanadium content. - Highlights: • Samples of the CuCr{sub 1−x}V{sub x}O{sub 2} series have been studied. • The V content increase induces a change from antiferromagnetism to spin glass. • A behavior characterisitic of a spin and dipole glass is demonstrated. • The ferroelectricity is shown to go from spin induced to relaxor. • Competing magnetic interactions are efficient way to generate multiglass state.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Synthesis, structural and magnetic characterisation of the fluorinated compound 15R-BaFeO{sub 2}F

The compounds 15R-BaFeO{sub 2}F and 15R-BaFeO{sub 2.27}F{sub 0.5} have been synthesised by the low temperature fluorination of 15R-BaFeO{sub 3−d}F{sub 0.2} using polyvinylidenedifluoride (PVDF) as a fluorination agent. The materials have been structurally characterised by Rietveld analysis of the X-ray- and HRPD-powder neutron diffraction data. A detailed analysis of bond valence sums suggests that the oxide and fluoride ions order on the different anion sites. A reinvestigation of our recently published structure (Clemens et al., 2013) [34] of 6H-BaFeO{sub 2}F is also reported and incorporation of fluoride in h-type layers is also confirmed in this compound. The magnetic moments for 15R-BaFeO{sub 2}F and 15R-BaFeO{sub 2.25}F{sub 0.5} align in the a/b-plane with antiferromagnetic alignment of the moments between adjacent layers, and are flipped by 90° as compared to the precursor compound. 15R-BaFeO{sub 2}F exhibits very robust antiferromagnetism with a Néel temperature between 300 and 400 °C. - Graphical abstract: The crystal and magnetic structure of the perovskite phase 15R-BaFeO{sub 2}F. - Highlights: • 15R-BaFeO{sub 2}F and 15R-BaFeO{sub 2.27}F{sub 0.5}were prepared via low temperature fluorination using PVDF. • A structural investigation of the compounds BaFeO{sub 2}F is presented in detail. • This analysis suggests ordering of O{sup 2−} and F{sup −} anions between different layers. • 15R-BaFeO{sub 2}F shows antiferromagnetic ordering at 300 K with T{sub N} ∼300–400 °C. • The magnetic moments align in the a/b-plane.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Crystals, magnetic and electronic properties of a new ThCr{sub 2}Si{sub 2}-type BaMn{sub 2}Bi{sub 2} and K-doped compositions

This is a report on the new 122 ternary transition-metal pnictide of BaMn{sub 2}Bi{sub 2}, which is crystallized from bismuth flux. BaMn{sub 2}Bi{sub 2} adopts ThCr{sub 2}Si{sub 2}-type structure (I4/mmm) with a=4.4902(3) Å and c=14.687(1) Å; it is antiferromagnetic with anisotropic magnetic susceptibility and semiconducting with a band gap of E{sub g}=6 meV. Heat capacity result confirms the insulating ground state in BaMn{sub 2}Bi{sub 2} with the electronic residual Sommerfeld coefficient of γ=0. The high temperature magnetization results show that magnetic ordering temperature is T{sub N} ∼400 K. Hole-doping in BaMn{sub 2}Bi{sub 2} via potassium in Ba{sub 1−x}K{sub x}Mn{sub 2}Bi{sub 2} results in metallic behavior for x=0.10(1), 0.32(1) and 0.36(1). With K-doping, more magnetically anisotropic behavior is observed. Although there is a downturn in electrical resistivity and low-field magnetization data below 4 K in>30%-doped crystals, there is no sign of zero resistance or diamagnetism. - Graphical abstract: Local moment antiferromagnet BaMn{sub 2}Bi{sub 2}, the first bismuthide with ThCr{sub 2}Si{sub 2} structure, turns metallic upon K-doping. Highlights: • BaMn{sub 2}Bi{sub 2} and Ba{sub 1−x}K{sub x}Mn{sub 2}Bi{sub 2} (0≤x<0.4) measuring up to 1 cm in length have been synthesized from Bi flux reactions. • BaMn{sub 2}Bi{sub 2} is the first bismuthide with ThCr{sub 2}Si{sub 2}-type structure. • BaMn{sub 2}Bi{sub 2} is a small gap semiconductor but, upon hole-doping, turns metallic with a downturn in resistivity below 4 K. • BaMn{sub 2}Bi{sub 2} is a local moment antiferromagnet with T{sub N} ∼400 K.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Five new Mn(II)/Co(II) coordination polymers constructed from flexible multicarboxylate ligands with varying magnetic properties

Five new Mn(II)/Co(II) coordination polymers [Mn{sub 2}(Adi){sub 2}(DMA)]{sub n} (1), [Mn{sub 2}(Adi){sub 2}(DMF)]{sub n} (2), [Mn{sub 4}(Adi){sub 4}(DMF){sub 2}]{sub n} (3), [Co{sub 4}(Adi){sub 4}(DMF){sub 2}]{sub n} (4) and ([Co{sub 3}(Cit){sub 2}(H{sub 2}O){sub 3}]·(H{sub 2}O)){sub n} (5) [Adi=adipate anion, Cit=citrate anion, DMA=N,N′-dimethylacetamide and DMF=N,N′-dimethylformamide] have been successfully constructed from two flexible multicarboxylate ligands under solvothermal conditions. Complexes 1 and 2 exhibit 2-D network featured 1-D Mn{sup II} chain, 3 and 4 are 3-D frameworks containing different 1-D carboxylate–metal chain, while 5 shows a 3-D structure based on Co{sub 6} wheel clusters. Magnetic investigations indicate antiferromagnetic behaviors for 1–4 and weak ferromagnetic behavior for 5 because of distinct linkage modes of metal ions. - Graphical abstract: Five new Mn(II)/Co(II) coordination polymers display 2-D/3-D structures containing 1-D carboxylate–metal chains or wheel clusters. Magnetic analyses reveal that they show antiferromagnetic, canted antiferromagnetic and weak ferromagnetic behaviors, respectively. Highlights: ●Five new Mn(II)/Co(II) coordination polymers have been synthesized. ●A complex-based Co{sub 6} wheel cluster was obtained. ●The different magnetic properties of the complexes are discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Ammonium–cobalt–nickel phosphates, NH{sub 4}[Co{sub 1−x}Ni{sub x}PO{sub 4}]·H{sub 2}O

The ammonium–cobalt–nickel phosphates, NH{sub 4}[Co{sub 1−x}Ni{sub x}PO{sub 4}]·H{sub 2}O (x=0.00, 0.34, 0.59, 0.70, 1.00), and the deuterated forms, ND{sub 4}[Co{sub 1−x}Ni{sub x}PO{sub 4}]·D{sub 2}O (x=0.00, 0.38, 0.48, 0.69, 0.85), have been synthesized under mild hydrothermal conditions and characterised using X-ray and neutron diffraction, chemical and thermal analysis, and magnetic measurements. Their crystal structures, including hydrogen positions, were determined by Rietveld refinement using single-crystal X-ray and neutron powder diffraction data. The space group of these orthorhombic crystals modifies as a function of their composition. The magnetic susceptibility and magnetization measurements of these ammonium–cobalt–nickel phosphates show antiferromagnetic behaviour, and the Neel temperature evolves from 5.5 K (x=0.00) up to 13.2 K (x=1.00). - Graphical abstract: We obtained single crystals for all the members of the family. In this series, although all crystals are orthorhombic, the space group changes as a function of the composition, showing how the single-crystal diffraction data is capable to manifest structural subtleties that had not been described before for this group of materials. All the investigated materials behave antiferromagnetically with ordering temperatures from 5.5 K up to 13.2 K. Display Omitted - Highlights: • The ammonium–cobalt–nickel phosphates, NH{sub 4}[Co{sub 1−x}Ni{sub x}PO{sub 4}]·H{sub 2}O (x=0.00, 0.34, 0.59, 0.70, 1.00) and the deuterated forms ND4[Co1-xNixPO4]·D{sub 2}O (x=0.00, 0.38, 0.49, 0.68, 0.85) have synthesized by hydrothermal synthesis. • The structural studies of these compounds are introduced as a function of the composition. • The magnetic studies show an antiferromagnetically behavior with ordering temperatures from 5.5 K to 13.2 K.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

New orthorhombic derivative of CaCu{sub 5}-type structure: RNi{sub 4}Si compounds (R=Y, La, Ce, Sm, Gd–Ho), crystal structure and some magnetic properties

The crystal structure of new YNi{sub 4}Si-type RNi{sub 4}Si (R=Y, La, Ce, Sm, Gd–Ho) compounds has been established using powder X-ray diffraction. The YNi{sub 4}Si structure is a new structure type, which is orthorhombic derivative of CaCu{sub 5}-type structure (space group Cmmm N 65, oC12). GdNi{sub 4}Si and DyNi{sub 4}Si compounds order ferromagnetically at 25 and 19 K, respectively whereas YNi{sub 4}Si shows antiferromagnetic nature. At 15 K, DyNi{sub 4}Si shows second antiferromagnetic-like transition. The magnetic moment of GdNi{sub 4}Si at 5 K in 50 kOe field is ∼7.2 μ{sub B}/f.u. suggesting a completely ordered ferromagnetic state. The magnetocaloric effect of GdNi{sub 4}Si is calculated in terms of isothermal magnetic entropy change and it reaches the maximum value of −12.8 J/kg K for a field change of 50 kOe near T{sub C} ∼25 K. - Graphical abstract: The RNi{sub 4}Si (R=Y, La, Ce, Sm, Gd–Ho) compounds crystallize in new YNi{sub 4}Si-type structure which is orthorhombic derivative of the basic CaCu{sub 5}-type structure. GdNi{sub 4}Si and DyNi{sub 4}Si compounds show the ferromagnetic-like ordering, whereas.YNi{sub 4}Si has the antiferromagnetic nature. The GdNi{sub 4}Si demonstrates the big magnetocaloric effect near temperature of ferromagnetic ordering. The relationship between initial CaCu{sub 5}-type DyNi{sub 5} and YNi{sub 4}Si-type DyNi{sub 4}Si lattices.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Synthesis and characterization of antiperovskite nitrides GaNCr{sub 3−x}Mn{sub x}

The effects of Mn-doping on the crystal structure, magnetic and electrical/thermal transport properties of GaNCr{sub 3−x}Mn{sub x} (0≤x≤1.5) have been investigated systematically. As a result, the lattice constant and the residual resistivity increase, while the residual resistivity ratio, electron thermal conductivity, and room-temperature carrier concentration decrease with increasing Mn-doping level. The ground state of parent compound GaNCr{sub 3} is nonmagnetic, interestingly, the ferrimagnetism and antiferromagnetism are observed in Mn-doped samples GaNCr{sub 3−x}Mn{sub x}. Correspondingly, around the antiferromagnetic transition of GaNCr{sub 3−x}Mn{sub x} the correlation effect is studied. Furthermore, the analysis of thermal conductivity data suggests that the electron thermal conductivity plays a major role in total thermal conductivity of GaNCr{sub 3} at low temperatures, while the phonon thermal conductivity is dominant for Mn-doped GaNCr{sub 3} in the whole temperature of 5–330 K. The positive values of Seebeck coefficient and Hall coefficient indicate that the nature of charge carrier is hole-type in GaNCr{sub 3−x}Mn{sub x}. - Graphical abstract: The Rietveld refinement and structural properties of GaNCr{sub 3−x}Mn{sub x}. Display Omitted - Highlights: • Polycrystalline GaNCr{sub 3−x}Mn{sub x} are synthesized by using the solid state reaction method. • A good quality of samples is verified by Rietveld refinement and RRR values. • Antiferromagnetic and ferromagnetic competitions are induced by Mn-doping. • We present a comprehensive understanding of physical properties of GaNCr{sub 3−x}Mn{sub x}.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

New tetragonal derivatives of cubic NaZn{sub 13}-type structure: RNi{sub 6}Si{sub 6} compounds, crystal structure and magnetic ordering (R=Y, La, Ce, Sm, Gd–Yb)

Novel RNi{sub 6}Si{sub 6} compounds adopt the new CeNi{sub 6}Si{sub 6}-type structure for R=La–Ce (tP52, space group P4/nbm N 125-1) and new YNi{sub 6}Si{sub 6}-type structure for R=Y, Sm, Gd–Yb (tP52, space group P4{sup ¯}b2N 117) that are tetragonal derivative of NaZn{sub 13}-type structure, like LaCo{sub 9}Si{sub 4}-type. The CeNi{sub 6}Si{sub 6}, GdNi{sub 6}Si{sub 6}, TbNi{sub 6}Si{sub 6}, DyNi{sub 6}Si{sub 6} and HoNi{sub 6}Si{sub 6} compounds are Curie–Weiss paramagnets down to ∼30 K, and do not order magnetically down to 5 K. However, the inverse paramagnetic susceptibility of LaNi{sub 6}Si{sub 6} does not follow Curie–Weiss law. The DyNi{sub 6}Si{sub 6} shows ferromagnetic-like saturation behaviour at 5 K in applied fields of 50 kOe, giving rise to a magnetic moment value of 6.5 μ{sub B}/f.u. in 50 kOe. The powder neutron diffraction study in zero applied filed indicates square modulated the c-collinear antiferromagnetic ordering of TbNi{sub 6}Si{sub 6} with K=[±1/4, ±1/4, 0] wave vector below ∼10 K. - Graphical abstract: Novel (La, Ce)Ni{sub 6}Si{sub 6} compounds adopt the new CeNi{sub 6}Si{sub 6}-type structure and (Y, Sm, Gd–Yb) adopt the new YNi{sub 6}Si{sub 6}-type structure that are tetragonal derivative of NaZn{sub 13}-type structure, like LaCo{sub 9}Si{sub 4}-type. The CeNi{sub 6}Si{sub 6}, GdNi{sub 6}Si{sub 6}, TbNi{sub 6}Si{sub 6}, DyNi{sub 6}Si{sub 6} and HoNi{sub 6}Si{sub 6} compounds are Curie–Weiss paramagnets down to ∼30 K, and do not order magnetically down to 4.2 K. The powder neutron diffraction study in zero applied filed indicates square modulated the c-collinear antiferromagnetic ordering of TbNi{sub 6}Si{sub 6} with K=[±1/4, ±1/4, 0] wave vector below ∼10 K. Display Omitted - Highlights: • The new (La, Ce)Ni{sub 6}Si{sub 6} compounds adopt the new CeNi{sub 6}Si{sub 6}-type structure. • The new (Y, Sm, Gd–Yb)Ni{sub 6}Si{sub 6} compounds adopt the new YNi{sub 6}Si{sub 6}-type structure. • TbNi{sub 6}Si{sub 6} has square modulated c-collinear antiferromagnetic ordering below ∼10 K.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

An interpenetrated pillared-layer MOF: Synthesis, structure, sorption and magnetic properties

A new three-dimensional porous framework [Co{sub 2}(bpdc){sub 2}(H{sub 2}bpz)]∙2(DMF)·5(H{sub 2}O) (1) (H{sub 2}bpdc=4,4′-biphenyldicarboxylic acid, H{sub 2}bpz=3,3′,5,5′-tetramethyl-4,4′-bipyrazole) has been solvothermally synthesized by employing mixed H{sub 2}bpdc and H{sub 2}bpz ligands. 1 is a pillared-layer framework based on a binuclear paddle-wheel Co{sub 2}(O{sub 2}C-R){sub 4} cluster, and exhibits a 2-fold interpenetrated 6-connected pcu topology. H{sub 2}bpz bridges Co{sub 2}(O{sub 2}C-R){sub 4} clusters with an angular coordination configuration to form interesting left- and right-handed helical chains. 1 possesses a two-dimensional porous system decorated by uncoordinated pyrazole –NH groups of H{sub 2}bpz, leading to high adsorption selectivities for CO{sub 2} over N{sub 2} and H{sub 2}. In addition, the strong antiferromagnetic interactions between the Co{sup 2+} ions in cluster were observed. - Graphical abstract: A new pillared-layer porous framework has been constructed by paddle-wheel Co{sub 2}(O{sub 2}C-R){sub 4} cluster and H{sub 2}bpdc–H{sub 2}bpz mixed ligands, displaying adsorption selectivity and antiferromagnetic properties. Display Omitted - Highlights: • We present a new pillared-layer framework based on paddle-wheel Co{sub 2}(O{sub 2}C-R){sub 4} cluster. • The framework possesses a 2-fold interpenetrated pcu topology. • The framework displays adsorption selectivity and antiferromagnetic properties.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Structural and property studies on metal–organic compounds with 3-D supramolecular network

Two carboxylato-bridged allomeric compounds, ([Cu{sub 2}(dbsa){sub 2}(hmt) (H{sub 2}O){sub 4}]{sub 1/2}·2H{sub 2}O){sub n} (1), ([Ni(dbsa)(H{sub 2}O){sub 2}]{sub 1/2}[Ni(dbsa)(hmt)(H{sub 2}O){sub 2}]{sub 1/2}·2H{sub 2}O){sub n} (2) (H{sub 2}dbsa=meso-2,3-dibromosuccinic acid, hmt=hexamethylenetetramine) have been synthesized and characterized by X-ray structral analyses. The metal ions have two kinds of coordination fashion in one unit, and bridged by carboxylate and hmt ligands along with weak interactions existing in the solid structure, forming a 3-D supramolecular network. Variable-temperature magnetic property studies reveal the existence of antiferromagnetic interactions in 1 and 2 with g=2.2, J{sub 1}=−3.5 cm{sup −1}, J{sub 2}=−2.8 cm{sup −1} for 1, and g=2.1, J=−3.5 cm{sup −1} for 2. - Graphical abstract: Variable-temperature magnetic property studies of two 3-D supramolecular compounds reveal the existence of antiferromagnetic interactions between the metal ions, through the effective super-exchange media. - Highlights: • Two 3-D allomeric Cu(II) and Ni(II) metal–organic compounds have been prepared. • The 3-D networks were constructed by coordination bonds, weak interactions and hydrogen bond interactions. • There are antiferromagnetic super-exchange interactions between the metal ions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

High-temperature X-ray diffraction measurements of fluorite-related rare earth antimonates Ln{sub 3}SbO{sub 7} (Ln=Nd, Tb) and their magnetic properties

Ternary rare-earth antimonates Ln{sub 3}SbO{sub 7} (Ln=rare earths) were prepared, and their structures were determined by X-ray diffraction measurements. They crystallize in an orthorhombic superstructure of cubic fluorite (space group Cmcm for Ln=La, Pr; Ccmm for Ln=Sm–Dy), in which Ln{sup 3+} ions occupy two different crystallographic sites (the 8-coordinated and 7-coordinated). For Ln=Nd, two phases with the Cmcm and Ccmm space groups coexist at room temperature. When the temperature was increased, the Nd{sub 3}SbO{sub 7} compound transformed into a single phase with the space group Cmcm. Through magnetic susceptibility measurements, an antiferromagnetic transition was observed at 3.0 K (Ln=Nd) and 7.8 K (Ln=Tb). Analysis of the magnetic specific heat for Tb{sub 3}SbO{sub 7} indicates that the 8-coordinated Tb ions magnetically orders at 7.8 K, and with furthermore decreasing temperature, the 7-coordinated Tb ions shows antiferromagnetic ordering at 3.0 K. - Graphical abstract: Temperature dependence of the specific heat divided by temperature (C{sub p}/T) and the magnetic entropy (S{sub mag}) for Tb{sub 3}SbO{sub 7}. Two-step magnetic transition has been observed. - Highlights: • The phase transition of Nd{sub 3}SbO{sub 7} is from the Ccmm space group to the Cmcm one. • Nd{sub 3}SbO{sub 7} shows an antiferromagnetic transition at 3.0 K. • For Tb{sub 3}SbO{sub 7}, two-step magnetic transition has been observed at 7.8 and 3.0 K.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗