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At least 1,621 records · Page 90
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Versatile lanthanide-azide complexes with azide/carboxylate/hydroxy mixed bridged chain exhibiting magnetic and luminescent properties

Two new lanthanide-azide complexes, [Ln{sub 2}(N{sub 3})(isonic){sub 2}(OH){sub 3}(Hisonic)(H{sub 2}O)]{sub n} (Ln=Yb for 1 and Tb for 2, isonic=isonicotinate), were obtained in hydrothermal condition. X-ray diffraction analysis indicated the two complexes are isomorphic chain structure in which the Ln{sup III} ions are mixed bridged by the azide anions, hydroxyl anions and carboxylate groups of the isonicotinate ligands. Further studies indicated weak antiferromagnetic interactions between the Ln{sup III} ions in 1 and 2, and complex 2 exhibit green sensitized Luminescent character of Tb{sup III} ion. - Graphical abstract: Two new 1D lanthanide-azide complexes, [Ln{sub 2}(N{sub 3})(isonic){sub 2}(OH){sub 3}(Hisonic)(H{sub 2}O)]{sub n} (Ln=Yb{sup III} for 1 and Tb{sup III} for 2, isonic=isonicotinate), were synthesized by hydrothermal reaction and exhibit interesting magnetism and fluorescence properties. Highlights: Black-Right-Pointing-Pointer The research provided a new method for synthesizing lanthanide-azide complexes. Black-Right-Pointing-Pointer The complexes have an interesting azide/hydroxyl/carboxylate mixed bridged1D chain structure. Black-Right-Pointing-Pointer The antiferromagnetic coupling between the complexes and 2 displays green luminescence.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Structural and magnetic characterisation of CoSb{sub 2}O{sub 4}, and the substitution of Pb{sup 2+} for Sb{sup 3+}

The nuclear and magnetic structures of the synthetic schafarzikite related material CoSb{sub 2}O{sub 4} have been determined from neutron powder diffraction data. The compound is tetragonal (P4{sub 2}/mbc) with refined lattice constants at 300 K of, a=8.49340(9) A, c=5.92387(8) A. The magnetic ordering is shown to be consistent with a C mode with moments aligned along [0 0 1]. Magnetic susceptibility measurements indicate a canted antiferromagnetic ground state, for which the ferromagnetic component shows unusually high coercivity. The thermal stability of CoSb{sub 2}O{sub 4} in air is reported. The substitution of Pb{sup 2+} for Sb{sup 3+} has been investigated and found to cause oxidation of both Co{sup 2+} to Co{sup 3+} and Sb{sup 3+} to Sb{sup 5+}. - Graphical Abstract: Structural changes on substitution of Pb{sup 2+} ions for Sb{sup 3+} ions in CoSb{sub 2}O{sub 4}. Highlights: Black-Right-Pointing-Pointer The structural details of CoSb{sub 2}O{sub 4} are reported for the first time. Black-Right-Pointing-Pointer The magnetic structure of CoSb{sub 2}O{sub 4} are reported for the first time. Black-Right-Pointing-Pointer The ordered magnetic structure has a canted antiferromagnetic arrangement. Black-Right-Pointing-Pointer The ferromagnetic component of the ordered arrangement has high coercivity. Black-Right-Pointing-Pointer Pb{sup 2+} can substitute for Sb{sup 3+} and oxidation of both Co{sup 2+} and Sb{sup 3+} occurs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Heat capacity and neutron diffraction studies on the frustrated magnetic Co{sub 2}(OH)(PO{sub 4}){sub 1-x}(AsO{sub 4}){sub x} [0{<=}x{<=}1] solid solution

The Co{sub 2}(OH)(PO{sub 4}){sub 1-x}(AsO{sub 4}){sub x} [0{<=}x{<=}1] solid solution exhibits a complex magnetic behaviour due to the bond-frustration in its magnetic structure. Heat capacity measurements of the (x=0.1-0.5) phases show a three-dimensional magnetic ordering ({lambda} anomaly) that shifts to lower temperatures and becomes broader as the AsO{sub 4}{sup 3-} content increases. For x=0.75, no significant feature was observed whereas for higher arsenate ion content, x=0.9 and 1, a small maximum was detected. The magnetic structures of solid solution are consistent with the existence of predominant antiferromagnetic superexchange interactions through the |OH| and |XO{sub 4}| (X=P and As) groups between the Co{sup +2} ions. The substitution of PO{sub 4}{sup 3-} by AsO{sub 4}{sup 3-} anions by more than 90% substantially modifies the magnetic exchange pathways in the solid solution, leading to an incommensurate antiferromagnetic structure in Co{sub 2}(OH)(PO{sub 4}){sub 1-x}(AsO{sub 4}){sub x} [x=0.9 and 1] phases. - Graphical abstract: Magnetic structures of Co{sub 2}(OH)(PO{sub 4}){sub 1-x}(AsO{sub 4}){sub x} [0{<=}x{<=}1]. The ordering of the magnetic moments of Co{sup 2+} is in c direction for the two crystallographic positions (dimers and chains) in all compounds. The unit cell is surrounded by a red line. Highlights: Black-Right-Pointing-Pointer Synthesis of a new adamite-type compounds, Co{sub 2}(OH)(PO{sub 4}){sub 1-x}(AsO{sub 4}){sub x} (0.1, 0.25, 0.5, 0.75, 0.9) phases. Black-Right-Pointing-Pointer Co{sub 2}(OH)(PO{sub 4}){sub 1-x}(AsO{sub 4}){sub x} (0-1) solid solution; magnetic frustrated system. Black-Right-Pointing-Pointer High resolution neutron powder diffraction to determine the crystal structures. Black-Right-Pointing-Pointer Incommensurate magnetic structures at low temperature. Black-Right-Pointing-Pointer Magnetostructural correlations in cobalt-based Co{sub 2}(OH)XO{sub 4} (X=P and As) insulation compounds.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

From spin induced ferroelectricity to dipolar glasses: Spinel chromites and mixed delafossites

Magnetoelectric multiferroics showing coupling between polarization and magnetic order are attracting much attention. For instance, they could be used in memory devices. Metal-transition oxides are provided several examples of inorganic magnetoelectric multiferroics. In the present short review, spinel and delafossite chromites are described. For the former, an electric polarization is evidenced in the ferrimagnetic state for ACr{sub 2}O{sub 4} polycrystalline samples (A=Ni, Fe, Co). The presence of a Jahn-Teller cation such as Ni{sup 2+} at the A site is shown to yield larger polarization values. In the delafossites, substitution by V{sup 3+} at the Cr or Fe site in CuCrO{sub 2} (CuFeO{sub 2}) suppresses the complex antiferromagnetic structure at the benefit of a spin glass state. The presence of cation disorder, probed by transmission electron microscopy, favors relaxor-like ferroelectricity. The results on the ferroelectricity of ferrimagnets and insulating spin glasses demonstrate that, in this research field, transition-metal oxides are worth to be studied. - Graphical abstract: Electric polarization as a function of temperature is measured up to T{sub C} in three chromite ferrimagnetic spinels. Largest values are reached for spinels with Jahn-Teller cations at the A site (Ni or Fe). Highlights: Black-Right-Pointing-Pointer Electric polarization is evidenced in the ferrimagnetic state of the chromite spinels. Black-Right-Pointing-Pointer Jahn-Teller cations at the A site of these spinels lead to larger polarization values. Black-Right-Pointing-Pointer Vanadium substituted at the Cr (or Fe) site of delafossites changes the antiferromagnetic state to spin glass. Black-Right-Pointing-Pointer Electric polarization is not the result of magnetic ordering but magnetic disordering in Cr or Fe delafossites. Black-Right-Pointing-Pointer Relaxor-type ferroelectricity or spin induced ferroelectricity can be observed in the delafossites.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Synthesis and properties of a new quadruple perovskite: A-site ordered PbMn{sub 3}Mn{sub 4}O{sub 12}

PbMn{sub 3}Mn{sub 4}O{sub 12} a quadruple perovskite was prepared by high pressure and high temperature synthesis. Powder X-ray diffraction (PXD) and differential scanning calorimetry reveal a structural phase transition at {approx}380 K. Rietveld refinement of the synchrotron room temperature data indicate rhombohedral symmetry (R-3) with a=6.43675(4) A and {alpha}=109.556(2) Degree-Sign . Similar 423 K PXD data refined in a body centered cubic cell (Im-3) with a=7.4283(9) A. The temperature variation of magnetization, shows a magnetic field dependent antiferromagnetic-like transition at 68 K, and dynamic fluctuations indicative of magnetic frustration. The semiconducting electrical behavior indicates a large decrease in the conductivity near 68 K. The temperature dependence of the real part of the dielectric constant, {epsilon}{sub real} increases dramatically at {approx}68 K, and shows relaxor-type ferroelectric behavior as a function of frequency. The intimate coupling of magnetic, electrical and dielectric properties at 68 K in PbMn{sub 3}Mn{sub 4}O{sub 12} suggests possible multiferroic behavior. - Graphical abstract: Resistance vs. temperature plot showing drastically increasing resistances at temperatures below 68 K (a). Formation of a frequency dependency of the dielectric constant between 68 K and ambient temperature (b). Sharp cusp in the magnetic susceptibility observed at 68 K which is suppressed with increasing magnetic field (c) indicates coupling of magnetic, electric and dielectric effects. Highlights: Black-Right-Pointing-Pointer PbMn{sub 3}Mn{sub 4}O{sub 12} a quadruple perovskite was prepared at high pressure. Black-Right-Pointing-Pointer A structural transition is seen at 380 K from space group R-3-to-Im-3. Black-Right-Pointing-Pointer An antiferromagnetic transition is observed at 68 K. Black-Right-Pointing-Pointer It is semiconducting with a large decrease in the conductivity near 68 K. Black-Right-Pointing-Pointer The temperature dependence of the dielectric constant increases dramatically at 68 K. Black-Right-Pointing-Pointer Coupling of magnetic, electric and dielectric behavior suggests multiferroicity.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Structural and physical properties of layered oxy-arsenides LnRuAsO (Ln=La, Nd, Sm, Gd)

Polycrystalline samples of LaRuAsO, NdRuAsO, SmRuAsO, and GdRuAsO have been synthesized and studied using powder x-ray diffraction, electrical transport, magnetization, and heat capacity measurements. Variations in structural properties across the series reveal a trend toward more ideal tetrahedral coordination around Ru as the size of the rare earth element is reduced. The lattice parameters of these Ru compounds show a more anisotropic response to variation in Ln than their Fe analogs, and significant anisotropy in thermal expansion is also observed. Transport measurements show metallic behavior, and carrier concentrations near 10{sup 21}-10{sup 22} electrons per cm{sup 3} are inferred from simple analysis of Hall effect measurements. Anomalies in resistivity, magnetization, and heat capacity indicate antiferromagnetic ordering of rare earth moments at 5 K for GdRuAsO, 4.5 K for SmRuAsO, and <2K for NdRuAsO. Magnetization measurements on LaRuAsO show no evidence of a magnetic moment on Ru. Observed behaviors are compared to those reported for similar Fe and Ru compounds. - Graphical abstract: Analysis of crystal structure, electrical transport, magnetic susceptibility, and heat capacity of LaRuAsO, NdRuAsO, SmRuAsO, and GdRuAsO. Highlights: Black-Right-Pointing-Pointer Experimental investigation of LaRuAsO, NdRuAsO, SmRuAsO, and GdRuAsO. Black-Right-Pointing-Pointer Anisotropic lattice response to changing Ln radius and temperature. Black-Right-Pointing-Pointer Ru coordination becomes more ideal as Ln radius is reduced. Black-Right-Pointing-Pointer Transport measurements reveal metallic conduction dominated by electrons. Black-Right-Pointing-Pointer Magnetic measurements indicate antiferromagnetic ordering Nd, Sm, and Gd moments.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Spin-lattice coupling in iron jarosite

We have studied the magnetoelectric coupling of the frustrated triangular antiferromagnet iron jarosite using Raman spectroscopy, dielectric measurements and specific heat. Temperature dependent capacitance measurements show an anomaly in the dielectric constant at T{sub N}. Specific heat data indicate the presence of a low frequency Einstein mode at low temperature. Raman spectroscopy confirms the presence of a new mode below T{sub N} that can be attributed to folding of the Brillouin zone. This mode shifts and sharpens below T{sub N}. We evaluate the strength of the magnetoelectric coupling using the symmetry unrestricted biquadratic magnetoelectric terms in the free energy. - Graphical abstract: Sketch of two connected triangles formed by Fe{sup 3+} spins (red arrows) in the hexagonal basal plane of potassium iron jarosite. An applied magnetic field (H) below the antiferromagnetic ordering temperature induces shifts of the hydroxy ligands, giving rise to local electrical dipole moments (blue arrows). These electric displacements cancel out in pairwise fashion by symmetry. Ligand shifts are confined to the plane and shown by shadowing. Highlights: Black-Right-Pointing-Pointer Evidence has been found for spin-lattice coupling in iron jarosite. Black-Right-Pointing-Pointer A new optical Raman mode appears below T{sub N} and shifts with temperature. Black-Right-Pointing-Pointer The magnetodielectric coupling is mediated by superexchange. Black-Right-Pointing-Pointer Symmetry of Kagome magnetic lattice causes local electrical dipole moments to cancel.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Neutron powder diffraction analysis of (Tm{sub 0.50}Ca{sub 0.50})MnO{sub 3} and (Lu{sub 0.50}Ca{sub 0.50})MnO{sub 3}

The crystal and magnetic structures of (Tm{sub 0.50}Ca{sub 0.50})MnO{sub 3} and (Lu{sub 0.50}Ca{sub 0.50})MnO{sub 3} have been investigated between 5 K and 300 K by means of high resolution neutron powder diffraction followed by Rietveld refinement and dc magnetic measurements. During cooling orbital ordering at the Mn sub-lattice takes place at T{sub OO}{approx}280 K in both compounds, inducing an orthorhombic to monoclinic phase transition. As the temperature is further decreased an antiferromagnetic CE-type structure occurs in both compounds at T{sub N}{approx}105 K. The comparison with other (Ln{sub 0.50}Ca{sub 0.50})MnO{sub 3} compounds reveals that at room temperature the average Jahn-Teller distortion increases sharply with the decrease of the ionic radius for lanthanides heavier than Sm. The ordered magnetic moment progressively decreases as the lanthanide ionic radius decreases on account of the decreased values of the Mn-O-Mn bond angles. - Graphical abstract: Rietveld refinement plot for (Tm{sub 0.50}Ca{sub 0.50})MnO{sub 3} obtained from neutron powder diffraction data collected at 5 K; the inset shows the CE-type spin ordering taking place at the Mn sub-lattice. Highlights: Black-Right-Pointing-Pointer The crystal and magnetic structures of (Tm{sub 0.50}Ca{sub 0.50})MnO{sub 3} and (Lu{sub 0.50}Ca{sub 0.50})MnO{sub 3} were analyzed by neutron powder diffraction. Black-Right-Pointing-Pointer Orbital ordering takes place below T{sub OO}{approx}280 K in both compounds. Black-Right-Pointing-Pointer An antiferromagnetic CE-type structure occurs in both compounds below T{sub N}{approx}105 K. Black-Right-Pointing-Pointer A Comparison with other (Ln{sub 0.50}Ca{sub 0.50})MnO{sub 3} compounds is reported.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Step-by-step assembly of 4d-4f-3d complex based on heptamolybdate anion

Four new complexes, (NH{sub 4}){sub 11.9}[Ln{sub 4.7}(MoO{sub 4})(H{sub 2}O){sub 23}(Mo{sub 7}O{sub 24}){sub 4}]{center_dot}xH{sub 2}O (Ln=Pr, x=34 (1); Ln=Nd, x=19 (2)), [NH{sub 4}]{sub 28}[Ce{sub 8}(MoO{sub 4}){sub 2}(H{sub 2}O){sub 31}(Mo{sub 7}O{sub 24}){sub 8}]{center_dot}74H{sub 2}O (3), and (NH{sub 4}){sub 26}[CoPr{sub 8}(MoO{sub 4}){sub 2}(H{sub 2}O){sub 33}(Mo{sub 7}O{sub 24}){sub 8}]{center_dot}54H{sub 2}O (4) have been synthesized and characterized by single-crystal and powder X-ray diffraction, CHN elemental analyses TGA analyses, IR and UV-Vis spectroscopy. Complex 1-3 are 0D compounds constructed by the connection between Ln{sup III} ions and [Mo{sub 7}O{sub 24}]{sup 6-} unit. In complex 4, the existence of Co{sup II} connects the polyanion clusters into 1D chain. The introduction of 3d metal (cobalt cation) and 4f metal (Ln=Pr{sup III}, Nd{sup III}, Ce{sup III}) encourages the coordination capability for [Mo{sub 7}O{sub 24}]{sup 6-} unit, which shows interesting coordination modes. The [Mo{sub 7}O{sub 24}]{sup 6-} unit in 1-4 shows three new coordination modes, connecting up to four metal cations. Complexes 1-4 show antiferromagnetic behavior via variable temperature magnetic study. The photoluminescence spectrum indicates the photoluminescence property for 4. - Graphical abstract: Heptamolybdate anion shows extraordinary coordination geometry in the presence of both lanthanide cation (Pr{sup III}) and transitional metal cation (Co{sup II}), which give rise to a new 4d-4f-3d complex. Black-Small-Square Highlights: Black-Right-Pointing-Pointer A new 4d-4f-3d complex that containing 1D chain was obtained and discussed. Black-Right-Pointing-Pointer New coordination geometry with higher coordination number of heptamolybdate. Black-Right-Pointing-Pointer Series of heptamolybdate contained complexes were synthesized and characterized. Black-Right-Pointing-Pointer Complexes mentioned above show antiferromagnetic behavior.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Crystal structure, spectroscopic, magnetic and electronic structure studies of a novel Cu(II) amino acid complex [Cu(L-arg){sub 2}(H{sub 2}O)]{sub 2}(P{sub 4}O{sub 12}){center_dot}8H{sub 2}O

Single crystals of a novel copper (II) complex with the amino acid L-arginine (L-arg) and cyclotetraphosphate, [Cu(L-arg){sub 2}(H{sub 2}O)]{sub 2}(P{sub 4}O{sub 12}){center_dot}8H{sub 2}O, were prepared in aqueous solution and were characterized by X-ray diffraction, spectroscopy (diffuse reflectance, UV-vis and IR) and thermal analysis. Magnetic measurements and electronic structure calculations were also performed. Crystal structure determination reveals that this compound has a nonsymmetrical atomic arrangement, containing mainly a binuclear [Cu(L-arg){sub 2}(H{sub 2}O)]{sub 2}{sup 4+} cation and an uncoordinated cyclotetraphosphate counter-anion (P{sub 4}O{sub 12}{sup 4-}). The tetravalent cation contains two independent Cu(II) ions in two different chemical environments. This compound exhibits an antiferromagnetic (AFM) to paramagnetic (PM) phase transition at a temperature (T{sub N}) lower than 2 K. The values of paramagnetic Curie-Weiss temperature ({theta}{sub cw}) and the exchange parameter (J/K{sub B}) emphasize the existence of an antiferromagnetic interaction between the neighboring copper ions. - Graphical abstract: The atomic arrangement of [Cu(L-arg){sub 2}(H{sub 2}O)]{sub 2}(P{sub 4}O{sub 12}){center_dot}8H{sub 2}O is built up of corrugated 2D-supramolecular layers and 1D-supramolecular anionic chain constructed by [P{sub 4}O{sub 12}(H{sub 2}O){sub 6}]{sub n}{sup 4n-}. Highlights: Black-Right-Pointing-Pointer Crystal structure of unusual cationic binuclear complex of [Cu(L-arg){sub 2}(H{sub 2}O)]{sub 2}(P{sub 4}O{sub 12}){center_dot}8H{sub 2}O. Black-Right-Pointing-Pointer An anti-syn equatorial-apical carboxylate bridging mode of both copper (II) centers. Black-Right-Pointing-Pointer [Cu(L-arg){sub 2}(H{sub 2}O)]{sub 2}{sup 4+} are held together by extensive H-bonds into wave-like layer. Black-Right-Pointing-Pointer Magnetic measurements exhibit an antiferomagnetic interaction between Cu(II). Black-Right-Pointing-Pointer Electronic structure calculation confirms the insulator state of the complex.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Investigation on three new metal carboxydiphosphonates: Syntheses, structures, magnetic and luminescent properties

A new multifunctionalized phosphoric acid, (2-(diphosphonomethylamino)nicotinic acid, Py(COOH)(NHCH--(PO{sub 3}H{sub 2}){sub 2}), H{sub 5}L{sup 1}), has been employed as ligand for the construction of new metal phosphonates. By reacting it with different metal chlorides under hydrothermal condition, three new transition metal phosphonates, namely, [Co{sub 2}(HL{sup 1})(H{sub 2}O){sub 5}][H{sub 2}O]{sub 3} (1), Zn(H{sub 3}L{sup 1}) (2) and [Cd(H{sub 3}L{sup 1})(H{sub 2}O){sub 2}][H{sub 2}O] (3) were successfully obtained. The single-crystal structure measurements indicated that the coordination mode of ligand H{sub 5}L{sup 1} is metal-dependant and results in different structures. For compound 1, it features 2D layered structure. Whereas compounds 2 and 3 have 1D chain structures. Under the excitation of 250 nm light, both compounds 2 and 3 show intraligand and ligand to metal charge transfer (LMCT) emission bands at about 415 and 420 nm, respectively. Magnetic study shows that compound 1 displays antiferromagnetic behavior. - Graphical abstract: Three new metal phosphonates were synthesized from a multifunctionalized phosphonate ligand and different metal chlorides. Their structures, thermal stabilities, luminescent and magnetic properties were characterized. Highlights: Black-Right-Pointing-Pointer Three new metal phosphonates were synthesized under hydrothermal conditions. Black-Right-Pointing-Pointer Compound 1 exhibits 2D layered structure. Black-Right-Pointing-Pointer Compounds 2 and 3 have 1D infinite chain structures. Black-Right-Pointing-Pointer Compound 1 displays antiferromagnetic behavior. Black-Right-Pointing-Pointer Compounds 2 and 3 show intraligand and ligand to metal charge transfer emission bands.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Spin reorientation and magnetization reversal in the perovskite oxides, YFe{sub 1-x}Mn{sub x}O{sub 3} (0{<=}x{<=}0.45): A neutron diffraction study

Members of the YFe{sub 1-x}Mn{sub x}O{sub 3} (0{<=}x{<=}0.45) family crystallize in the GdFeO{sub 3} type orthorhombic perovskite structure (space group Pnma) where the Fe and Mn ions are disordered at the 4b crystallographic site. Upon substitution of Mn at the Fe-site in the canted antiferromagnetic YFeO{sub 3} (T{sub N}=640 K), a first-order spin-reorientation transition occurs at a temperature, T{sub SR}, where the magnetic structure changes from the canted to a collinear state. With increasing Mn-concentration, T{sub SR} increases whereas T{sub N} decreases. Neutron diffraction studies on the x=0.4 sample reveal that the spin structure changes from {Gamma}{sub 4} to {Gamma}{sub 1} below T{sub SR}. Intriguingly, when x=0.4 and 0.45, a temperature-induced magnetization reversal is observed below a compensation temperature T{sup Low-Asterisk} (T{sup Low-Asterisk }<T{sub SR}<T{sub N}). The reversal is explained on the basis of a ferrimagnetic ground state resulting from antiferromagnetic coupling of the canted moments of Fe-O-Fe and Mn-O-Mn with that of Fe-O-Mn ordering. - Graphical abstract: Neutron diffraction study on YFe{sub 1-x}Mn{sub x}O{sub 3} demonstrates a spin-reorientation transition from canted {Gamma}{sub 4} to collinear symbol {Gamma}{sub 1} spin structure. A temperature-induced magnetization reversal is observed for x=0.4 and 0.45. Highlights: Black-Right-Pointing-Pointer Neutron diffraction study on YFe{sub 1-x}Mn{sub x}O{sub 3}. Black-Right-Pointing-Pointer Spin-reorientation from spin structure {Gamma}{sub 4} to {Gamma}{sub 1}. Black-Right-Pointing-Pointer Magnetization reversal phenomenon in disordered perovskite oxides, YFe{sub 1-x}Mn{sub x}O{sub 3} and YCr{sub 1-x}Mn{sub x}O{sub 3}. Black-Right-Pointing-Pointer Presence of tunable positive and negative magnetocaloric effects in YFe{sub 1-x}Mn{sub x}O{sub 3}.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Syntheses, characterization and magnetic properties of two novel inorganic-organic tungstoferrites, [Fe{sup III}{sub 4}(H{sub 2}O){sub 2}(B-{alpha}-Fe{sup III}W{sub 9}O{sub 34}){sub 2}]{sup 10-}

Interaction of the lacunary [{alpha}-SbW{sub 9}O{sub 33}]{sup 9-} with Fe{sup 3+} in the presence of organic amines under hydrothermal conditions yields two novel inorganic-organic hybrid tungstoferrites [dapH{sub 2}]{sub 3}[enH{sub 2}][enH]Na[Fe{sub 4}(H{sub 2}O){sub 2}(FeW{sub 9}O{sub 34}){sub 2}]{center_dot}7H{sub 2}O (dap=1,2-diaminopropane, en=ethylenediamine) (1) and [dapH{sub 2}]{sub 5}[Fe{sub 4}(H{sub 2}O){sub 2}(FeW{sub 9}O{sub 34}){sub 2}]{center_dot}11H{sub 2}O (2), which have been characterized by IR, elemental analysis, UV-Vis, TG and single-crystal X-ray diffraction. Both 1 and 2 consist of two [B-{alpha}-Fe{sup III}W{sub 9}O{sub 34}]{sup 11-} units joined by a rhomb-like tetranuclear iron cluster. Interestingly, 1 displays a new example of 1D chain-like architecture, in which adjacent [Fe{sub 4}(FeW{sub 9}O{sub 34}){sub 2}]{sup 10-} anions are interconnected by two unusual W-O-Fe bridges. Meanwhile, the neighboring chains are further assembled by Na{sup +} ions, forming the 2D extended network. 2 exhibits a discrete dimeric TMSP structure constructed from two trivacant [B-{alpha}-Fe{sup III}W{sub 9}O{sub 34}]{sup 11-} subunits encapsulating a rhomb-like tetranuclear iron cluster with five isolated diprotoned dap molecules. Magnetic measurements indicate that antiferromagnetic exchange interactions are dominant in the hexanuclear {l_brace}Fe{sub 6}O{sub 22}{r_brace} clusters in 1 and 2. - Graphical abstract: Two novel inorganic-organic hybrid tungstoferrites were synthesized from the reaction of lacunary [{alpha}-SbW{sub 9}O{sub 33}]{sup 9-} with Fe{sup 3+} under hydrothermal conditions and structurally characterized. The magnetic properties of them were also studied. Highlights: Black-Right-Pointing-Pointer 1 represents the first example of 1D chain-like {l_brace}Fe{sub 4}(FeW{sub 9}){sub 2}{r_brace} tungstoferrite. Black-Right-Pointing-Pointer Two [B-{alpha}-Fe{sup III}W{sub 9}O{sub 34}]{sup 11-} units linked via a rhomb-like tetranuclear iron cluster. Black-Right-Pointing-Pointer Adjacent {l_brace}Fe{sub 4}(FeW{sub 9}){sub 2}{r_brace} are interconnected by unusual W--O--Fe bridges. Black-Right-Pointing-Pointer Antiferromagnetic exchange interactions are dominant in the {l_brace}Fe{sub 6}O{sub 22}{r_brace} cluster.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Synthesis, structural and magnetic characterisation of the fully fluorinated compound 6H-BaFeO{sub 2}F

The compound 6H-BaFeO{sub 2}F (P6{sub 3}/mmc) was synthesised by the low temperature fluorination of 6H-BaFeO{sub 3-d} using polyvinylidenedifluoride (PVDF) as a fluorination agent. Structural characterisation by XRD and NPD suggests that the local positions of the oxygen and fluorine atoms vary with no evidence for ordering on the anion sites. This compound shows antiferromagnetic ordering at room temperature with antiparallel alignment of the magnetic moments along the c-axis. The use of PVDF also allows the possibility of tuning the fluorine content in materials of composition 6H-BaFeO{sub 3-d}F{sub y} to any value of 0<y{<=}1. In addition, the oxygen content, and therefore the iron oxidation state, can be tuned by applying different partial pressures of oxygen during the reaction. - Graphical abstract: The crystal structure of the hexagonal perovskite phase 6H-BaFeO{sub 2}F. Highlights: Black-Right-Pointing-Pointer The crystal structure of the hexagonal perovskite phase 6H-BaFeO{sub 2}F. Black-Right-Pointing-Pointer H-BaFeO{sub 2}F and 6H-BaFeO{sub 3-d}F{sub y} were prepared via low temperature fluorination using PVDF. Black-Right-Pointing-Pointer A structural investigation of the compounds BaFeO{sub 2}F is presented in detail. Black-Right-Pointing-Pointer This analysis suggests differences for the local coordination of O{sup 2-} and F{sup -} anions. Black-Right-Pointing-Pointer H-BaFeO{sub 2}F shows antiferromagnetic ordering at 300 K. Black-Right-Pointing-Pointer The magnetic moments align parallel to the a-axis.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Cu{sub 2}Mn{sub 1-x}Co{sub x}SnS{sub 4}: Novel keesterite type solid solutions

A new family of Cu{sub 2}Mn{sub 1-x}Co{sub x}SnS{sub 4} chalcogenides has been synthesized by conventional solid-state reactions at 850 Degree-Sign C. The reactions products were characterized by powder X-ray diffraction (XRD), energy-dispersive X-ray analysis (SEM-EDS), Raman spectroscopy and magnetic susceptibility. The crystal structures of two members of the solid solution series Cu{sub 2}Mn{sub 0.4}Co{sub 0.6}SnS{sub 4} and Cu{sub 2}Mn{sub 0.2}Co{sub 0.8}SnS{sub 4} have been determined by single-crystal X-ray diffraction. Both phases crystallize in the tetragonal keesterite-type structure (space group I4{sup Macron }). The distortions of the tetrahedral volume of Cu{sub 2}Mn{sub 0.4}Co{sub 0.6}SnS{sub 4} and Cu{sub 2}Mn{sub 0.2}Co{sub 0.8}SnS{sub 4} were calculated and compared with the corresponding differences in the Cu{sub 2}MnSnS{sub 4} (stannite-type) end-member. The compounds show nearly the same Raman spectral features. Temperature-dependent magnetization measurements (ZFC/FC) and high-temperature susceptibility indicate that these solid solutions are antiferromagnetic. - Graphical abstract: View along [100] of the Cu{sub 2}Mn{sub 1-x}Co{sub x}SnS{sub 4} structure showing tetrahedral units and magnetic measurement ZFC-FC at 500 Oe. The insert shows the 1/{chi}-versus-temperature plot fitted by a Curie-Weiss law. Highlights: Black-Right-Pointing-Pointer Cu{sub 2}Mn{sub 1-x}Co{sub x}SnS{sub 4} solid solutions belong to the family of compounds adamantine. Black-Right-Pointing-Pointer Resolved single crystals of the solid solutions have space group I4{sup Macron }. Black-Right-Pointing-Pointer The distortion of the tetrahedral volume of Cu{sub 2}Mn{sub 1-x}Co{sub x}SnS{sub 4} were calculated. Black-Right-Pointing-Pointer These solid solutions are antiferromagnetic.

36 MATERIALS SCIENCE↗
DOE OSTI2013

High-pressure synthesis, crystal structure and magnetic property of ilmenite-type FeGeO{sub 3}

We synthesized well-crystallized ilmenite-type FeGeO{sub 3} to investigate its structural and magnetic properties. Ilmenite-type FeGeO{sub 3} were synthesized by high-pressure synthesis technique using a Kawai-type multi-anvil apparatus. Their structural and magnetic properties were examined by XRD analysis with Rietveld refinement, transmission electron microscopy, Moessbauer spectroscopy and SQUID-magnetization measurements. The subsequent annealing after the high-pressure synthesis was effective to improve the crystallinity of the ilmenite-type FeGeO{sub 3}. The primary particle size of ilmenite-type FeGeO{sub 3} was {approx}15 nm. Some particles seemed to be covered with non- or poorly crystalline phase even after the annealing, and others showed a lamellar microstructure parallel to the (0 0 1) plane. Theilmenite-type FeGeO{sub 3} showed typical antiferromagnetic behavior with the Neel temperature of 79 K. - Graphical abstract: Crystal structure, transmission electron micrograph and temperature dependent susceptibility of ilmenite-type FeGeO{sub 3}. Highlights: Black-Right-Pointing-Pointer Ilmenite-type FeGeO{sub 3}, a novel polymorphism of FeGeO{sub 3} was successfully synthesized. Black-Right-Pointing-Pointer It was synthesized by using high pressure technique at 23.5 GPa at 500 Degree-Sign C. Black-Right-Pointing-Pointer Subsequent annealing in vacuum was effective to improve the crystallinity. Black-Right-Pointing-Pointer Its primary particle size was {approx}15 nm, and some grains had lamellar microstructure. Black-Right-Pointing-Pointer It showed typical antiferromagnetic behavior with the Neel temperature of 79 K.

36 MATERIALS SCIENCE↗
DOE OSTI2013

A neutron diffraction study of structural distortion and magnetic ordering in the cation-ordered perovskites Ba{sub 2}Nd{sub 1−x}Y{sub x}MoO{sub 6}

The cation ordered perovskites Ba{sub 2}Nd{sub 1−x}Y{sub x}MoO{sub 6} (0.04≤x≤0.35) have been synthesised by solid-state techniques under reducing conditions at temperatures up to 1350 °C. Rietveld analyses of X-ray and neutron powder diffraction data show that these compounds adopt a tetragonally distorted perovskite structure. The tetragonal distortion is driven by the bonding requirements of the Ba{sup 2+} cation that occupies the central interstice of the perovskite; this cation would be underbonded if these compounds retained the cubic symmetry exhibited by the prototypical structure. The size and charge difference between the lanthanides and Mo{sup 5+} lead to complete ordering of the cations to give a rock-salt ordering of Nd{sup 3+}/Y{sup 3+}O{sub 6} and MoO{sub 6} octahedra. The I4/m space group symmetry is retained on cooling the x=0.1, 0.2 and 0.35 samples to low temperature ca. 2 K. Ba{sub 2}Nd{sub 0.90}Y{sub 0.10}MoO{sub 6} undergoes a gradual distortion of the MoO{sub 6} units on cooling from room temperature to give two long trans bonds (2.001(2) Å) along the z-direction and four shorter apical bonds (1.9563(13) Å) in the xy-plane. This distortion of the MoO{sub 6} units stabilises the 4d{sup 1} electron in the d{sub xz} and d{sub yz} orbitals whilst the d{sub xy} orbital is increased in energy due to the contraction of the Mo–O bonds in the xy-plane. This bond extension along z is propagated through the structure and gives a negative thermal expansion of −13×10{sup −6} K{sup −1} along c. The overall volumetric thermal expansion is positive due to conventional expansion along the other two crystallographic axes. With increasing Y{sup 3+} content this distortion is reduced in x=0.2 and eliminated in x=0.35 which contains largely regular MoO{sub 6} octahedra. The x=0.1 and x=0.2 show small peaks in the neutron diffraction profile due to long range antiferromagnetic order arising from ordered moments of ca. 2 μ{sub B}. - Graphical Abstract: The distortion in the molybdenum crystal field is continuously adjusted by chemical composition of the perovskite. Highlights: ► Introducing Y{sup 3+} into Ba{sub 2}NdMoO{sub 6} stabilises tetragonal symmetry to 2 K. ► A distortion of the ligand field around the Mo{sup 5+} 4d{sup 1} cation confers electronic stabilisation. ► The size of the distortion is progressively reduced with increasing Y{sup 3+} content. ► Distortion gives negative thermal expansion along z and antiferromagnetic order at T≤15 K.

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

Solid solution studies of layered honeycomb-ordered phases O₃–Na₃M₂SbO₆ (M=Cu, Mg, Ni, Zn)

Complete solid solutions with the composition Na₃M 2–x M´ x SbO₆ where M, M´=Cu, Mg, Ni, Zn have been synthesized by conventional solid state techniques and were investigated using X-ray diffraction, magnetic susceptibility and optical measurements. All compositions crystallize in a monoclinic unit cell and exhibit a layered structure with a honeycomb cationic ordering within the slabs. These compounds also exhibit Curie–Weiss behavior at high temperature and the magnetic moment values verify the presence of Cu²⁺ and/or Ni²⁺. The antiferromagnetic order of Na₃Ni₂SbO₆ is suppressed upon substitution of Ni²⁺ with Mg²⁺ or Zn²⁺. The spin gap observed in Na₃Cu₂SbO₆ is also suppressed by substitution of Cu²⁺ with Mg²⁺ or Zn²⁺. The Na₃Ni 2–x Cu x SbO₆ compositions follow an expected transition from an antiferromagnetic ordering to the spin gap of the copper end member. The estimated band gaps for these compounds have been determined from diffuse reflectance measurements. - Graphical abstract: Complete solid solutions with the composition Na₃M 2–x M´ x SbO₆ where M, M´=Cu, Mg, Ni, Zn have been synthesized using conventional solid state techniques and were investigated using X-ray diffraction, magnetism and optical measurements. Based on an ionic radii point of view the lattice parameter shifting in the composition containing copper are opposite of what would be expected. The Cu²⁺ is Jahn–Teller active which distorts the C2/m cell, increasing the β angle between the a and c parameters and explains this shifting pattern. Highlights: • The solid solutions O₃–Na₃M 2–x M´ x SbO₆(M, M´=Cu, Mg, Ni, Zn) were synthesized. • These compounds crystallize in the C2/m space group. • The Jahn–Teller active Cu²⁺ causes distortion of the monoclinic cell. • The Cu²⁺ spin gap magnetic properties are diluted upon 25% substitution. • All compositions are insulating and have large band gaps.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗