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The mixed-metal cluster compound (PPh4)[Fe2Ir2(CO)12{μ3-Au(PPh3)}], which has a trigonal bipyramidal core consisting of five atoms of three different Mössbauer isotopes, was studied by 193Ir, 197Au and 57Fe Mössbauer spectroscopy. The nature and the chemical character of the atoms located at the different sites are discussed with respect to their Mössbauer spectra. [ABSTRACT FROM AUTHOR]

Structural studies of Zn2+Fe 2 3 + (P2O7)2 and Cu0.5Zn0.5Fe2(P2O7)2 were made using powder X-ray diffraction and refined by Rietveld method. Both phosphates crystallize in an orthorhombic structure with Pnma space group. Magnetometry measurements showed that below TN = 5.6 (1), Zn2+Fe 2 3 + (P2O7)2 becomes antiferromagnetic and the TN = 14 K is attributed to Cu0.5Zn0.5Fe2(P2O7)2. Mössbauer studies at room temperature and low temperature were performed in both samples. [ABSTRACT FROM AUTHOR]

Presents a study which observed the magnetism of ternary compounds RE[sub6]Fe[sub16]X (X=Cu, Ag, Au, Zn, Cd, Hg). Details on the experiment; Information on the compound formation and structural chemistry; Refinement of the crystal structure of Nd[sub6]Fe[sub13]Au.

Iron oxide nanoparticles are of great scientific interest due to their huge versatility of applications. The oxidation process of magnetite to maghemite is difficult to monitor as both iron oxide polymorphs possess connatural chemical properties. Especially the surface composition and reactivity of these nanosystems, which are most relevant for interactions with their environment, are not completely understood. Here, the oxidation of magnetite is investigated under mild and harsh conditions in order to understand the oxidation behaviour and the chemical stability of transition forms. Therefore, the oxidation process, is investigated with Raman, Mössbauer and X-ray photoelectron spectroscopy as well as X-ray diffraction and magnetometry. The multi-analytical approach allows new insights into surface composition and rearrangement according to respective different depth profiles. For both conditions investigated, the ferrous iron components are oxidised prior to structural changes in the Fe–O vibrations and crystal structure. The process starts from the outer layers and is acid catalysed. Oxidation leads to a decrease of magnetisation which still remains higher than 54 emu g−1. The charge and surface reactivity can be affected by the different oxidation methods and the irreversible adsorption of acid molecules. Biocompatibility and catalytic properties of iron oxide nanoparticles open doors to future applications. [ABSTRACT FROM AUTHOR]

Samples from a pre-Columbian furnace used for copper alloy smelting on the Pampa de Chaparrí in northern Peru during the Middle to Late Sicán Period (AD 900–1375) were studied by Mössbauer spectroscopy, X-ray diffraction and X-ray fluorescence. The data thus obtained allow conclusions as to the temperatures and oxidation-reduction conditions prevaling at different positions inside the furnace during the smelting process. [ABSTRACT FROM AUTHOR]

The normal A-site spinels MnAlO, FeAlO, CoAlO, as well as related mixed (MnFeAlO) and partially inverted (FeAlO) spinels have been studied by μSR. The magnetic ions are subject to magnetic frustration by competing interactions. In all materials and at all temperatures the μSR spectra consist of two signals suggesting a bimodal distribution of the fluctuation rates of magnetic moments. A characteristic temperature T is found in each compound, representing either a magnetic phase transition into a long-range ordered state (MnAlO, FeAlO) or the formation of a spin liquid phase (FeAlO, CoAlO, MnFeAlO). The magnetic ground state of MnAlO shows coexistence of antiferromagnetic and spin liquid phases. In FeAlO and CoAlO long-range order is suppressed altogether, the ground state can be characterized as a fast relaxing spin liquid coexisting with a small fraction of paramagnetic spins. The partial replacement of Mn by Fe in MnFeAlO prevents long-range order and leads to a spin liquid state in the low temperature limit. The partial occupancy of B-sites by magnetic ions in FeAlO strengthens the exchange coupling, allowing the formation of long-range magnetic order at a rather high temperature (~100 K). Magnetic phase diagrams are presented demonstrating that for the studied compounds the magnetic properties are determined by the degree of frustration. [ABSTRACT FROM AUTHOR]

Polynuclear iron catalysts are interesting materials because of their novel properties. In the future they may help to replace high cost and hazardous heavy metal catalysts by efficient, non toxic and economic iron compounds. In this work, we present some preliminary results on a novel polynuclear oxo-bridged iron catalyst. The chemical environment of the metal species (Fe) was studied under Gif-type conditions (Fe catalyst/Zn/O2 in pyridine/acetic acid) with cyclohexene as substrate. Such Gif-type catalysts are able to catalyse the selective oxidation of alkanes and alkenes. The characterization was done by Mössbauer spectroscopy and nuclear inelastic scattering. In order to identify the intermediate species during the reaction (selective oxidation using molecular O2), a freeze-quench technique was used. This also helps to understand the kinetics of the chemical reaction. [ABSTRACT FROM AUTHOR]

197Au and 119Sn Mössbauer spectroscopy was used to study the effect of tin on the formation of gold nanoparticles in gold ruby glasses containing 200 ppm of gold and up to 2 wt.% of tin. The tin was found to speed up the formation of the metallic nanoparticles during annealing at temperatures around 600°C and to cause very small particles with sizes of only a few nanometres to be formed, whereas fewer but larger particles are formed in the absence of tin. This has consequences for the colour of the glasses, which changes from purple red for virtually tin-free to brown for tin-rich glasses. [ABSTRACT FROM AUTHOR]

A specialized form of extracellular matrix (ECM) surrounds subpopulations of neurons termed ‘perineuronal nets’ (PNs). These PNs form highly anionic charged structures in the direct microenvironment of neurons, assumed to be involved in local ion homeostasis since they are able to scavenge and bind redox-active iron ions. The quantity and distribution of iron-charged PNs of the extracellular matrix in the rat brain areas of the cortex and the red nucleus was investigated using the powerful combination of Particle-Induced X-ray Emission (PIXE) and Mössbauer spectroscopy. These studies reveal that the iron is bound to the PNs as Fe(III). PNs in both brain regions accumulate up to three to five times more Fe3+ than any other tissue structure in dependency on the applied Fe concentration with local amount maximums of 480 mmol/l Fe at PNs. [ABSTRACT FROM AUTHOR]

The isomer shifts of the measured Mössbauer spectra are in accordance with quantum chemical calculations and both techniques showed that the studied iridium(I) complexes have a strong covalent character, namely, there are a direct σ donation of the ligands into the 6s orbital of Ir. The coordination of further π-acceptor ligands decreases the population of 6s orbital. The obtained quadrupole splittings detect significant difference among the electric field gradients at the nucleus of iridium in the discussed coordination compounds. In this paper we present the first attempt to obtain Mössbauer parameters of 193Ir by DFT calculations. The change in the measured quadrupole splittings due to the coordiantion of tetracyanoethylene to central iridium was excellently reproduced by theoretical calculation using ZORA scheme. The magnetization measurements proved that IrI has diamagnetic, singlet electronic structure in all the studied compounds. This finding was in accordance with density functional calculations as well. Nuclear magnetic resonance investigations on 31P nucleus could detect the decrease of the electric field gradient at the nucleus of 193Ir in IrCl(CO)(PPh3)2 due to the coordination of C60 to the central iridium atom. [ABSTRACT FROM AUTHOR]

We present an overview on an extended study of Celtic ceramics from the oppidum of Manching and from some contemporary Celtic sites. The results of neutron activation analysis, thin section microscopy and Mössbauer spectroscopy are combined with the existing detailed archaeological typology to provide information on the provenance of Celtic pottery and on details of its production. The data indicate that there was only very limited exchange of material but far reaching transfer of technology. [ABSTRACT FROM AUTHOR]