At 320 K, the crystal structure of CeRuSn is commensurate with the related CeCoAl-type of structure by the doubling of the c lattice parameter. However, with lowering the temperature it becomes ...incommensurate with x and z position parameters at all three elemental sites being modulated as one moves along the c-axis. The resulting crystal structure can be conveniently described within the superspace formalism in (3 + 1) dimensions. The modulation vector, after initially strong temperature dependence, approaches a value close to qnuc = (0 0 0.35). Below TN = 2.8 (1) K, CeRuSn orders antiferromagnetically with a propagation vector qmag = (0 0 0.175), i.e. with the magnetic unit cell doubled along the c-axis direction with respect to the incommensurate crystal structure. Ce moments appear to be nearly collinear, confined to the a−c plane, forming ferromagnetically coupled pairs. Their magnitudes are modulated between 0.11 and 0.95 μB as one moves along the c-axis.
FePt nanoparticles inside ordered mesoporous silica SBA‐15 were synthesized via incipient wetness impregnation and subsequent thermal treatments in reductive atmosphere. The porous matrix is used to ...prevent sintering and agglomeration during the fcc–FePt to fct–FePt phase transition. According to magnetic measurements and Mössbauer spectroscopic studies, the resulting FePt@SBA‐15 composites are ferromagnetic.
Pyrite (FeS 2), arsenopyrite (FeAsS) and löllingite (FeAs 2) are exceptional gold concentrators on Earth; yet the exact redox and structural state of this "invisible" gold and the forces driving its ...intake and release by these minerals remain highly controversial. Here we applied high resolution X-ray absorption spectroscopy to Au-bearing pyrite and iron sulfarsenides from hydrothermal deposits and their synthetic analogues. We show that Au preferentially enters octahedral Fe structural sites Au(As,S) 6 enriched in As, by forming respectively AuAs 1-3 S 5-3 , AuAs 3 S 3 ⋯AuAs 6 and AuAs 6 atomic units in arsenian pyrite (>0.1-1.0 wt. % As), arsenopyrite and löllingite, implying a formal oxidation state of Au II in the minerals. In contrast, in As-poor pyrite, Au is dominantly chemisorbed as Au I S 2 moieties in much lower concentrations. Combined with experimental data on Au mineral-fluid partitioning, our findings imply a universal control exerted by arsenic on gold incorporation in iron sulfides and sulfarsenides via coupled Au-As redox reactions. These reactions account for the observed variations in invisible gold contents in the minerals from different hydrothermal deposit types and enable quantitative prediction of iron sulfarsenide ability in controlling gold concentration and distribution in hydrothermal systems.
The new high temperature form (HT) of the ternary germanide CeTiGe was prepared by annealing at 1373 K. The investigation of HT-CeTiGe by x-ray powder diffraction shows that the compound crystallizes ...in the tetragonal CeScSi type structure (space group I4/mmm; a=414.95(2) and c=1590.85(10) pm as unit cell parameters). Electrical resistivity, thermoelectric power, magnetization and specific heat measurements performed down to 2 K on HT-CeTiGe reveal a non-magnetic strongly correlated electron system; the specific heat divided by temperature attains a value of 0.635 J mol(-1) K(-2) at 2 K. The comparison of the physical properties of the two crystallographic modifications of CeTiGe suggests a decrease of the hybridization J(cf) between 4f(Ce) and conduction electrons in the sequence LT-CeTiGe Formula: see text-CeTiGe (CeScSi type).
The magnetocaloric properties of the ferromagnetic compounds GdScSi (TC = 354(2) K) and GdScGe (TC = 349(2) K) (tetragonal CeScSi-type structure refined from single crystal diffractometer data, space ...group I4/mmm) have been determined. The field dependence of the magnetic entropy ΔSm change and of the refrigerant capacity RC have been obtained from magnetization measurements. At the TC Curie temperature, ΔSm for GdScSi and GdScGe is respectively equal to 2.5 and 3.3 J/kgGd K for a magnetic field change of 2 T; the values are comparable to those determined previously for Gd7Pd3 and Gd4Bi3 which exhibit also a TC-temperature higher than room temperature. Both microstructural and the analysis of the magnetocaloric response are used to assess the single phase nature of the samples.
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► Crystal structure of GdScSi and GdScGe data. ► GdScSi and GdScGe exhibit ferromagnetism below 354 and 349 K ► Magnetocaloric properties of GdScSi and GdScGe.
CeRhSb was prepared from the elements by arc-melting. A single crystal of this antimonide was investigated on the basis of X-ray diffractometer data: TiNiSi type; Pnma; a = 741.58(9), b = 461.80(9), ...c = 785.77(8) pm; wR2 = 0.0960; 645 F 2 values; 20 variable parameters. Hydrogenation leads to the formation of the new hydride CeRhSbH0.2 which adopts the same structure but with a slightly larger unit cell volume: a = 742.2(2), b = 462.5(2), c = 787.7(2) pm; wR2 = 0.1444; 443 F 2 values; 20 variable parameters. The rhodium and antimony atoms build up three-dimensional RhSb networks with Rh−Sb distances ranging from 268 to 287 pm. The cerium atoms fill distorted hexagonal channels within these networks with one short Ce−Rh contact (310 pm in CeRhSb and 311 pm in CeRhSbH0.2). Susceptibility and specific heat measurements on CeRhSbH0.2 reveal antiferromagnetic ordering at T N = 3.6(2) K. The experimental magnetic moment in the paramagnetic region is 2.68(5) μB/Ce atom. Magnetization measurements below T N reveal a spin-flip transition in the range 1.6−2.4 T. Resistivity data show metallic behavior and the characteristics of a Kondo system. Thermoelectric power measurements show a distinct maximum around 106 K with a value of 24 μV/K. 121Sb Mössbauer spectroscopic data for CeRhSb and CeRhSbH0.2 at 78 K show only one antimony site. The isomer shift is slightly smaller for the hydrogenated sample indicating a slightly higher electron density at the antimony nuclei of CeRhSbH0.2.
Li0.44Eu3B3N6 was synthesized from the metathesis reaction of Li3BN2 and EuCl3 at 850°C. Li0.44Eu3B3N6 crystallizes in the trigonal space group R3¯c (No. 167) with a=12.0225(2)Å, c=6.8556(2)Å and ...Z=6. In the crystal structure, isolated, planar cyclic B3N69− units are charge-balanced by the mixed-valence Eu3+/Eu2+ and Li+ cations. Li+ occupies partially (44%) the Wyckoff site 6b and is sandwiched between the B3N69− anions. Mössbauer spectroscopy results show the resonance lines of Eu2+ and Eu3+, respectively, indicating the heterogeneous mixed valency of the Eu atoms. X-Band ESR investigations between 5 and 300K reveal an intense signal over the whole temperature range originating from Eu2+. Magnetic susceptibility measurements indicate a Curie–Weiss behavior with an experimental effective magnetic moment of μeff=8.28μB per formula unit.
Single crystals of Li0.44Eu3B3N6 was obtained from the metathesis reaction of Li3BN2 and EuCl3.151Eu Mössbauer, ESR and magnetic susceptibility measurements reveal the heterogeneous mixed valency of the Eu atoms. Display omitted
•Single crystals of Li0.44Eu3B3N6 was obtained from the metathesis reaction of Li3BN2 and EuCl3 at 850°C.•Crystal structure is built up by isolated, planar cyclic B3N69− units which are surrounded by mixed valence Eu3+/Eu2+.•Li+ occupies partially (44%) the site 6b and is sandwiched between the B3N69− anions.•The 151Eu Mössbauer spectroscopy, electron spin resonance spectroscopy and magnetic susceptibility measurements confirm the heterogeneous mixed valency of Eu.
The reaction of either V2F6·4H2O or a mixture of 60 wt % VF2·4H2O and 40 wt % VF3·3H2O with a water-saturated gaseous mixture of 15–20 vol % hydrogen in argon leads to the formation of a new ...polymorph of V3O5 crystallizing in the orthorhombic anosovite-type structure. Quantum-chemical calculations show that the anosovite-type structure is about 15 kJ/mol less stable than the corresponding monoclinic Magnéli phase. In addition, there are no imaginary modes in the phonon density of states, supporting the classification of the anosovite-type phase as a metastable V3O5 polymorph. Susceptibility measurements down to 3 K reveal no hint for magnetic ordering.
Two different types of fluxes, namely sodium based and chloride based fluxes were used to grow Cr substituted barium and strontium hexaferrite ferrite crystals, (Sr,Ba)Fe12 − xCrxO19 at comparatively ...low temperatures of about 1300 °C. The sodium based flux led to growth of larger crystals up to 5 mm, but with only minor Cr contents x ≤ 0.07. From the chloride based flux the obtained Cr contents are significantly higher with x = 5.7 (Sr) and x = 3.4 (Ba), however, crystals reach only sizes in the sub-mm range. X-ray absorption spectroscopy data support exclusively isovalent substitution of Fe3+ by Cr3+ even for very low Cr contents. 57Fe Mößbauer spectroscopy reveals Cr to preferentially occupy the six-fold by oxygen coordinated site at 12k and, to a lower degree, 2a and 4f2 in space group P63/mmc. All characteristic magnetic properties drop upon Cr substitution, e. g., the Curie temperature from 728 K for pure BaFe12O19 to 465 K for BaFe8.6Cr3.4O19, the saturation magnetization from 71 emu/g to 29.7 emu/g and the coercive field from 363 Oe to 45 Oe.
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•Growth of large crystals of Cr substituted (Ba,Sr)Fe12O19 from two different fluxes.•Cr-substitution in a large range of compositions.•Cr/Fe order revealed by Mößbauer spectroscopy.•All Cr and Fe in oxidation state +3 present.•Anisotropic magnetic properties determined.
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