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Compounds that exhibit the spin crossover effect are known to show a change of spin states through external stimuli. This reversible switching of spin states is accompanied by a change of the properties of the compound. Complexes, like iron (II)-triazole complexes, that exhibit this behavior at ambient temperature are often discussed for potential applications. In previous studies we synthesized iron (II)-triazole complexes and implemented them into electrospun nanofibers. We used Mössbauer spectroscopy in first studies to prove a successful implementation with maintaining spin crossover properties. Further studies from us showed that it is possible to use different electrospinning methods to either do a implementation or a deposition of the synthesized solid SCO material into or onto the polymer nanofibers. We now used a solvent in which both, the used iron (II)-triazole complex [Fe(atrz)3](2 ns)2 and three different polymers (Polyacrylonitrile, Polymethylmethacrylate and Polyvinylpyrrolidone), are soluble. This shall lead to a higher homogeneous distribution of the complex along the nanofibers. Mössbauer spectroscopy and other measurements are therefore in use to show a successful implementation without any significant changes to the complex. [ABSTRACT FROM AUTHOR]

Carbonatite is an igneous rock that is composed mainly of carbonate minerals and silicates. It is recently applied as fertilizer due to its high content of calcite and dolomite. This study presents a physical and chemical characterization of the Spanish River Carbonatite (SRC) and its application as fertilizer is tested. The chemical composition obtained by X-ray fluorescence and Energy Dispersive X-ray analyses indicates that Ca, Fe and Si are the main contained elements. Calcite and SiO2 are the principal mineralogical phases as detected by X-ray diffraction. Fourier transform infrared spectroscopy confirms the presence of calcite, silicates and also organic material and water. It also suggests the presence of vermiculite. Thermal analysis reveals only a one-step reaction that corresponds to the decomposition of calcite. Mössbauer spectroscopy performed at room temperature do not show magnetic order between the iron moments instead it shows Fe2+ and Fe3+ doublets in M1 and M2 octahedral sites belonging to vermiculite. At 50 K, we observe that the isomer shift increases their values due to the second order Doppler shift. SQUID magnetometry measurements reveal that most of the sample contains paramagnetic domains assigned to the silicates and calcite components. However, under low applied fields, a tiny signal for Verwey transition appears at 124 K (suggesting the presence of magnetite) although screened by the strong paramagnetic signal of the main components. The SRC has been tested as potential fertilizer on sweet cucumber (Solanum muricatum) which responded positively to the application to carbonatite as an amendment, expressing itself in high foliar biomass. [ABSTRACT FROM AUTHOR]

Nitriding of austenitic stainless steel (ASS) causes changes to its surface, and it is widely used in technological applications. The extreme sensitivity of the formed layer not only to the nitriding process but also to its parameters (or nitriding conditions) leads to an infinite number of samples, making it difficult to compare it with results from different authors. The nitrided layer has a gradient of the nitrogen content profile. This, added to the presence of non-stoichiometric phases and the presence of induced residual stress, forms a very heterogenous probed area. Another issue is that despite being relatively well studied, the crystallographic structure of the expanded austenite, which is the main structure formed, is not well established. Considering this, many challenges remain concerning the characterization of the microstructure of the formed layer, mainly because of the limitations of the local structure characterization tools, whose results can be extremely difficult to interpret. Moreover, recent results suggest that the surface proximity may substantially affect the structure in this outermost region, and therefore even a few tenths of a micron must be carefully characterized, which increases the complexity of this system. In this context, Mössbauer spectroscopy (MS) is an interesting exploratory technique, which, if correlated with other techniques, can support this challenging task. However, regardless of the intrinsic complexity of this spectroscopy, interpreting the Mössbauer spectrum is not straightforward, requiring not only a solid understanding of the nitrided ASS system, but also a careful correlation with the results of other techniques. In this study, these points are cautiously detailed and the implications in the MS analyses are widely discussed. Finally, some ways of improving the analyses are outlined and discussed. [ABSTRACT FROM AUTHOR]

Mössbauer spectra of Feridex, an MRI enhancement agent, show that it contains superparamagnetic γ-Fe2O3 nanoparticles. From spectra in magnetic fields applied at room temperature the magnetic moment of the particles was measured to be 11,250 μB, from which the diameters of the single-domain particles are estimated to be about 8 nm. This is smaller than the hydrodynamic particle size of 30 nm which includes a protective coating of dextran. The particles are monodisperse, as shown by the continuous change from a broad superparamagnetic line to a magnetic 6-line pattern as the temperature is lowered below the blocking temperature TB of about 90 K. The magnetic moments and blocking temperature are consistent with those of γ-Fe2O3 samples of known sizes. [ABSTRACT FROM AUTHOR]

X-ray diffraction (XRD), Fields Emission Scanning Electron Microscope (FE-SEM) with EDS and Mössbauer Spectroscopy (MS), were applied to investigate a newly fallen solid piece of debris named the Aba Panu meteorite, after a city in south western Nigeria (Lat: N 08° 14′ 25.7″ and Long: E 003° 33′ 47.0″). Matching X-ray diffraction results, together with the FE-SEM analysis confirms the presence of four kinds of iron-bearing minerals, namely olivine, pyroxene, kamacite (Fe-Ni alloys) and troilite (FeS). The Mössbauer spectra recorded at 295 K and 78 K consist of two strong paramagnetic doublets emanating from olivine of quadrupole splitting 2.9 mm/s and pyroxene of quadrupole splitting 2.1 mm/s. These are superimposed on two magnetic sub-spectra attributed to kamacite and troilite phases. From the Mössbauer sub-spectra absorption area, the ratio of the olivine absorption area to the pyroxene absorption area indicates that the meteorite can be classified as an L-ordinary chondrite. The mole fraction of the Fe end-member of olivine (fayalite) and the orthopyroxene (ferrosilite) calculated from the EDS data will be used to identify the petrographic type of the meteorite. [ABSTRACT FROM AUTHOR]

The series ZnxMg1-xNiFeO4(0.0≤ x ≤1.0) were prepared by the conventional solid state double sintering ceramic techniques and studied using X-ray diffraction (XRD), and Mössbauer spectroscopy techniques. The diffraction patterns of all samples show single phase cubic spinel structure. Mössbauer spectroscopy measurements at liquid nitrogen temperature show an ordered magnetic structure with well resolved tetrahedral and octahedral sites. Data analysis were performed in order to investigate the magnetic properties of the materials and their cation distribution behavior between the tetrahedral and octahedral sites. These will be discussed based on the substitution of both diamagnetic divalent. [ABSTRACT FROM AUTHOR]

We synthesised a series of Iron(II)-triazole compounds and used the electrospinning procedure to incorporate spin crossover compounds (SCO) into polylactic acid polymer fibers. Composite fiber/SCO compounds of [Fe(NH-trz)](BF) as well as [Fe(Htrz)(trz)]BF were investigated via Mössbauer spectroscopy at 293 K and 77 K. The Mössbauer studies show that the spin crossover behavior is maintained in the polymer matrix. [ABSTRACT FROM AUTHOR]

Trivalent iron sulfide (Fe S ) particles were synthesized using a modified polyol method. These particles exhibited a needle-like shape (diameter = 10-50 nm, length = 350-1000 nm) and generated a clear XRD pattern. Mössbauer spectra of the product showed a paramagnetic doublet at room temperature and distributed hyperfine magnetic splitting at low temperature. The Curie temperature of this material was determined to be approximately 60 K. The data suggest that the Fe S had a structure similar to that of maghemite ( γ-Fe O ) with a lattice constant of a = 10.6 Å. The XRD pattern calculated from this structure was in agreement with the experimental pattern and the calculated hyperfine magnetic field was also equivalent to that observed in the experimental Mössbauer spectrum. [ABSTRACT FROM AUTHOR]

Magnetic properties of perovskite oxides, SrSnFeO ( x ≤ 0.15), substituted with nonmagnetic Ca and Ti ions were studied. XRD patterns showed the orthorhombic structure (close to tetragonal) of (SrCa)(SnFe)O and Sr(SnFeTi)O. The cell volumes decreased with the increase of Ca and Ti doping rates. Although Ti-substituted Sr(Sn, Fe)O showed small saturation magnetizations as compared with non-Ti substituted one, the magnetization increased a little with Ti doping rates up to 15%. On the other hand, all Ca-substituted Sr(Sn, Fe)O showed larger saturation magnetization than non-Ca substituted one. Two doublets of Fe and a doublet of Fe were observed in Mössbauer spectra of Ca-substituted Sr(Sn, Fe)O with weak ferromagnetism, and two sextets of high spin Fe were additionally observed in Mössbauer spectra of Ca-doped Sr(Sn, Fe)O with relatively strong ferromagnetism. When Sr(Sn, Fe)O were further codoped with Ca and Ti ions, they showed the stable and enhanced ferromagnetic properties. It is considered that magnetic polarons among high spin Fe species are overlapped by shrinking or deforming the crystal structure of perovskite oxides. That is the magnetism induced by a chemical pressure of perovskite oxides. [ABSTRACT FROM AUTHOR]

We synthesised a series of seven mononuclear Schiff base coordination compounds. The symmetric pentadentate NO-donating ligands were prepared by the condensation of N-(2-aminoethyl)-1,2-ethanediamine with either 5-bromosalicylaldehyde or 5-chlorosalicylaldehyde. The octahedral coordination sphere is completed by different pseudohalide mondentate N-donating ligands. All complexes have been analysed by Mössbauer spectroscopy, ESI-MS and IR spectroscopy. The Mössbauer spectra at room temperature reveal a doublet, which are related to the high spin state (S = 5/2) of the iron(III) centres. [ABSTRACT FROM AUTHOR]

SrSnFeSbO was prepared by a sol-gel and thermal annealing method. The lattice parameters of SrSnFeSbO (x = 0.04-0.15) decreased with the increase of Fe doping rates. All samples showed ferromagnetic behavior together with a paramagnetic component, relatively strong ferromagnetism for SrSnFeSbO and SrSnFeO with Fe doping rates over 6% and 8%, respectively The Sb doping leads to the ferromagnetic behavior for the samples with the low-concentration of Fe dopant. Sn Mössbauer spectra of SrSnFeO and SrSnFeO provided a broad doublet under a magnetic field of 0.85 T. The doublet could be analyzed as a magnetic sextet with 0.76 T. In Fe Mössbauer spectra of SrSnFeO under zero and 0.85 T different line intensity ratios of two sextets were observed. It suggests that the magnetic spin structure of SrSnFeO is transversely ferrimagnetic. [ABSTRACT FROM AUTHOR]

Fe Mössbauer spectroscopy has provided precise and accurate iron redox ratios Fe/Fe in ilmenite, FeTiO, found within kimberlite samples from the Catoca and Camatxia kimberlite pipes from N.E. Angola. Ilmenite is one of the key indicator minerals for diamond survival and it is also one of the iron-bearing minerals with iron naturally occurring in one or both of the oxidation states Fe and Fe. For this reason it is a good indicator for studying oxygen fugacities ( fO) in mineral samples, which can then be related to iron redox ratios, Fe/Fe. In this paper we demonstrate that the oxidation state of the ilmenite mineral inclusion from sampled kimberlite rock is a key indicator of the oxidation state of the host kimberlite assemblage, which in turn determines the genesis of diamond, grade variation and diamond quality. Ilmenite samples from the two different diamondiferous kimberlite localities (Catoca and Camatxia) in the Lucapa graben, N.E. Angola, were studied using Mössbauer spectroscopy and X-Ray Diffractometry, in order to infer the oxidation state of their source regions in the mantle, oxygen partial pressure and diamond preservation conditions. The iron redox ratios, obtained using Mössbauer spectroscopy, show that the Catoca diamond kimberlite is more oxidised than kimberlite found in the Camatxia pipe, which is associated within the same geological tectonic structure. Here we demonstrate thatFe Mössbauer spectroscopy can assist geologists and mining engineers to effectively evaluate and determine whether kimberlite deposits are economically feasible for diamond mining. [ABSTRACT FROM AUTHOR]

Zinc ferrite nano-crystals were synthesized by a microwave assisted combustion route with varying the urea to metal nitrates (U/N) molar ratio The process takes only a few minutes to obtain Zinc ferrite powders. The Effect of U/N ratio on the obtained phases, particle size, magnetization and structural properties has been investigated. The specimens were characterized by XRD, Mössbauer and VSM techniques. The sample prepared with urea/metal nitrate ratio of 1/1 was a poorly crystalline phase with very small crystallite size. A second phase is also detected in the sample. The crystallite size increases while the second phase decrease with increasing the urea ratio. The saturation magnetization and coercivity of the as prepared nano-particles changed with the change of the U/N ratio. The powder with the highest U/N ratio showed the presence of an unusually high saturation magnetization of 16 emu/g at room temperature. The crystallinity of the as prepared powder was developed by annealing the samples at 700 C and 900 C. Both the saturation magnetization ( Ms) and the remnant magnetization ( Mr) were found to be highly dependent upon the annealing temperature. Mössbauer studies show magnetic ordering in the powder even at room temperature. The Mössbauer and the magnetic parameters of this fraction are different from the standard values for bulk zinc ferrite. [ABSTRACT FROM AUTHOR]

Layered rocksalt type oxides, such as Li(NiMnCo)O, are widely used as the cathode active materials of lithium-ion rechargeable batteries. Because the nickel ions are associated with the role of the charge compensation at discharge and charge, the Ni Mössbauer measurements at 6 K using synchrotron radiation were performed to reveal the role of Ni. The Ni ions of the active materials play two roles for the redox process between the charge and discharge states of lithium-ion batteries. Half of the total Ni ions change to the low-spin Ni with Jahn-Teller distortion from the Ni ions of the discharge state. The remainder exhibit low-spin state divalent Ni ions. [ABSTRACT FROM AUTHOR]

The iron oxide FeO, the mineral magnetite sometimes called ferrosoferric oxide, is notoriousy non-stoichiometric even in bulk form so its formula may be written FeO. In nanoparticle form, where it has applications in medicine and information technology, it is even more susceptible to oxidation. In this paper we report synthesis and studies of superparamagnetic FeO nanoparticles with controlled diameters of 5.3, 10.6 and 11.9 nm. In room temperature spectra, departures from stoichiometry δ of up to 0.02 were estimated from the relative amounts of Fe / Fe and from their isomer shifts. This cannot be used for very small particles of diameter 10.6 nm and less as they are superparamagnetic at room temperature and do not show hyperfine splitting owing to fast relaxation. Such particles have promise for use in enhancing MRI signals. The magnetic spectrum is restored by the application of a relatively small magnetic field (10 kG). As the temperature is lowered the relaxation slows down and 6-line magnetic hyperfine patterns appear below a blocking temperature T. The values of T obtained are lower than those of many other researchers reported in the literature, suggesting that our particles are less affected by magnetic interactions between them. At low temperatures all the spectra are similar and closely resemble that of bulk FeO confirming that departures from stoichiometry are small. [ABSTRACT FROM AUTHOR]

Mg oxides doped with 1 % Fe were prepared by a sol-gel method, and annealed at various temperatures. Nano-size Mg oxides were characterized by Mössbauer spectrometry, magnetization and XRD measurements. The crystalline size of MgO increases with increase of annealing temperature. Samples annealed at 600 °C and 800 °C gave only doublet peaks of paramagnetic Fe in Mössbauer spectra although Fe doping into MgO induced a distorted structure and showed weak ferromagnetism. It is considered that the magnetic property is due to defect induced magnetism by doping Fe into MgO. For a sample heated at 1000 °C, it is found from low temperature Mössbauer spectra that Fe species are located at the core and shell of fine MgFeO grains and diluted in MgO matrix. [ABSTRACT FROM AUTHOR]

Mössbauer spectroscopy was used to examine Fe-containing microporous materials zeolite X and AlPO-5 designed for the reduction of Cr(VI) to Cr(III) and Cr(III) uptake. XRD, XRF, EPR and XPS were used to provide supporting information. AlPO-5 was found to only incorporate inactive Fe(III), whilst Fe(II) and Fe(III) were identified in zeolite X across a distribution of sites. Fe coordinates to oxygen atoms belonging to both water molecules and framework positions. EPR confirmed these findings and showed how the site distribution narrows upon dehydration. XPS showed that a distribution of Fe sites exists at the sample surface. Mössbauer spectroscopy was also used to track oxidation and reduction processes in Fe-zeolite X. Over time, gradual Fe oxidation takes place in air-exposed samples. Reduction under hydrogen flow increases the populations of low oxidation state Fe; as the reaction time increases, Fe(II) populations first increase, then decrease as Fe(0) is evolved. [ABSTRACT FROM AUTHOR]

A fluorozirconate glass (ZBLAN) containing BaCl nanocrystals doped with divalent Eu is a promising material for x-ray image plates for medical diagnosis. Since it is known that Eu readily oxidizes to Eu , which reduces fluorescence efficiency of the image plates, Eu Mössbauer spectroscopy was used in this work to monitor the Eu oxidation state of the samples during degradation over time in the presence of ambient humidity. In addition, Mössbauer spectroscopic experiments show that the oxidation state has already changed during the glass melt: The sample made from 5 mol% EuCl contained 78 % EuCl + 22 % EuCl deduced from the relative areas of the absorption lines. The sample made from 2.5 mol% EuCl + 2.5 mol% EuCl contained 37 % EuCl + 63 % EuCl, i.e. 26 % of the original EuCl was oxidized to EuCl . [ABSTRACT FROM AUTHOR]

Nurina-003 is a Group LL5/br Ordinary Chondrite meteorite which was recovered in the Nullarbor Desert (Australia) in 1986. The degree of weathering is classified as moderate to severe. We have characterised the Fe-bearing phases in Nurina-003 by Fe Mössbauer Spectroscopy over the temperature range 5-295 K. The spectra are dominated by Olivine and also contain Pyroxene, Troilite and a Ferric component that is (super)paramagnetic at 295 K. We clearly see the effects of the magnetic ordering of the Olivine phase in the 5 K spectrum. [ABSTRACT FROM AUTHOR]

The measurement of the Mössbauer effect in a system excited with a periodic perturbation can provide information about it. For that purpose, the Mössbauer absorption of a source-absorber set which hyperfine parameters are well known, is measured at a constant relative velocity (i.e. at a defined spectral energy). The resulting Mössbauer absorption periodic signal provides information of the sample ac perturbation response. This approach has been used time ago to measure small tympanic vibrations (mechanical perturbations). In this work we present an extension of the vibration experiments, by measuring them at various absorber-source relative velocities within a constant-velocity strategy. As a demonstration test, the frequency response of a piezoelectric diaphragm in the 100 Hz–5 kHz range is obtained with a custom electronic counter. The experiments are performed using a 57Co( Rh) source and a 25- $\upmu$ m-thick stainless-steel absorber fixed to a piezoelectric diaphragm. Phase shifts and amplitude vibrations with velocities in the range from 1.5 $\upmu$ m/s to 20 mm/s are well characterized, extending the linearity limit well beyond the earlier suggested one of 1 mm/s. [ABSTRACT FROM AUTHOR]

Long term gamma spectroscopy experiments involving single-channel analyzer equipment depend upon thermal stability of the detector and its associated high-voltage supply. Assuming constant discrimination levels, a drift in the detector gain impacts the output rate, producing an effect on the output spectrum. In some cases (e.g. single-energy resonant absorption experiments) data of interest can be completely lost. We present a digital self-adapting discrimination strategy that tracks emission line shifts using statistical measurements on a predefined region-of-interest of the spectrum. It is developed in the form of a synthesizable module that can be intercalated in the digital processing chain. It requires a moderate to small amount of digital resources and can be easily activated and deactivated. [ABSTRACT FROM AUTHOR]

The magnetic properties and Mössbauer results for SnO 2 doped with 57Fe are reviewed, and the values of isomer shift and quadrupole splitting are compared with the results obtained by ab initio calculations. It is concluded that the exchange interactions between oxygen defects and magnetic atoms are responsible for long range magnetic interactions of dilute Fe ions dispersed in SnO 2. Fe atom precipitated clusters may be formed in highly Fe doped SnO 2 samples by annealing at relatively high temperatures for several hours. The reduction of the particle size to nano-scale dimensions induces magnetization, which can be associated with oxygen defects. We have measured the nuclear inelastic scattering (NIS) spectra of Fe oxides, and 57Fe and (Co or Mn) doped SnO 2 synthesized mainly by sol–gel methods and we have derived the vibration density of states (VDOS). The local phonons are sensitive to the presence of precipitated clusters. [ABSTRACT FROM AUTHOR]

Three L5-type ordinary chondrite meteorites recovered from the Nullarbor Region of Western Australia were studied by 57Fe Mössbauer spectroscopy: Kinclaven–001, Camel Donga–007 and Gunnadorah–002. The relative amounts of the various Fe-bearing phases including the primary minerals (Olivine, Pyroxene, Troilite and Fe-Ni metal) and the ferric alteration products (Goethite, Maghemite/Magnetite) were obtained to determine the percentage of iron converted to Fe 3 +  by weathering processes. These data allow us to estimate the terrestrial age of Kinclaven–001 at 1,700 ± 1,300 yrs. [ABSTRACT FROM AUTHOR]

We have applied 57Fe nuclear resonance vibrational spectroscopy (NRVS) for the first time to study the dynamics of Fe centers in Iron-sulfur protein crystals, including oxidized wild type rubredoxin crystals from Pyrococcus furiosus, and the MoFe protein of nitrogenase from Azotobacter vinelandii. Thanks to the NRVS selection rule, selectively probed vibrational modes have been observed in both oriented rubredoxin and MoFe protein crystals. The NRVS work was complemented by extended X-ray absorption fine structure spectroscopy (EXAFS) measurements on oxidized wild type rubredoxin crystals from Pyrococcus furiosus. The EXAFS spectra revealed the Fe-S bond length difference in oxidized Pf Rd protein, which is qualitatively consistent with the crystal structure. [ABSTRACT FROM AUTHOR]

The complementary investigation techniques, Mössbauer spectroscopy, transmission electron microscopy with selected area electron diffraction (TEM/SAED), X-ray diffraction (XRD) have been used to investigate the fate of the Valea lui Stan, Romania, gold-ore nanoscale-minerals during the long time of residence in the waste dumps. The preliminary investigations showed such waste dumps to contain significant amount of metals which cannot be identified by conventional methods. An intense research activity started up in order to evaluate the possibilities to recycle Valea lui Stan waste dumps and to recover metals by chemical or phytoextraction procedures. The waste dumps naturally show different mineral constituents with clay minerals as major phases, observed by XRD-technique. Although the waste dumps materials have whitish-yellowish colours, MÖSSBAUER technique evidences the presence of the finely dispersed iron bearing minerals. The authors are focusing to inspect and analyze Fe-compounds in the samples collected from Valea lui Stan's waste dumps in order to identify the magnetic phases by Mössbauer technique. [ABSTRACT FROM AUTHOR]

In the present work, we report application of simultaneous fitting procedures to Mössbauer data acquired on the Plains of Gusev Crater by the MIMOS II spectrometer on board the Mars Exploration Rover Spirit. Based on a quantitative measure of spectrum quality, the 34 best of the ∼126 spectra acquired on the Plains are grouped together for a single simultaneous fit with a common least-squares criterion. Fitted values for the quadrupole splitting (QS) of olivine (Ol) from 200 K to 260 K are shown to lie between reported trend lines for Fo50 and Fo30 olivine, with a temperature gradient of (−11.2 ± 1.2) × 10 mm/s/K, a nearly five-fold improvement in precision over the previously reported value, enabling extrapolation to QS(Ol) = (2.93 ± 0.01) mm/s at 295 K. QS of pyroxene fit as a single doublet exhibits a temperature gradient of (−7.3 ± 2.3) × 10 mm/s/K. [ABSTRACT FROM AUTHOR]

Investigations based on Fe Mössbauer spectroscopy and powder X-ray diffraction report the existence of siderite in a manganese ore deposit in the city of Conselheiro Lafaiete, Minas Gerais, Brazil. Mössbauer parameters at 110 K indicated the isomorphous substitution of Fe in siderite structure by other cations such as Ca and Mg, resulting in the distortion of siderite structure. The proposed mechanism suggests the formation of siderite and it is consistent with the process of carbonate formation in reducing environments. [ABSTRACT FROM AUTHOR]

Quality of Mössbauer spectra is strongly related to the performance of source velocity modulator. Traditional electromechanical driving techniques demand hard-edged square or triangular velocity waveforms that introduce long settling times and demand careful driver tuning. For this work, the behavior of commercial velocity transducers and drive units was studied under different working conditions. Different velocity reference waveforms in constant-acceleration, constant-velocity and programmable-velocity techniques were tested. Significant improvement in spectrometer efficiency and accuracy was achieved by replacing triangular and square hard edges with continuous smooth-shaped transitions. A criterion for best waveform selection and synchronization is presented and attainable enhancements are evaluated. In order to fully exploit this driving technique, a compact microprocessor-based architecture is proposed and a suitable data acquisition system implementation is presented. System linearity and efficiency characterization are also shown. [ABSTRACT FROM AUTHOR]

The evolution of nanocrystalline n-MgFeO by high-energy milling a mixture of MgO and α-FeO for periods of between 0 h and 12 h has been investigated by neutron diffraction in addition to previous Mössbauer, XRD and HRTEM measurements. Complete transformation of the milled products to n-MgFeO only occurs on milling to ∼8 h even though the average particle size decreases to < ∼10 nm after milling for 2 h. The applied field Mössbauer spectra of n-MgFe2O4 can be well described by two subspectra representing core and shell regions with different cation distributions and spin canting angles. The neutron pattern of nanocrystalline MgFeO is described well by two components comprising nanoparticles of core and shell dimensions ∼7(1) nm and ∼0.7(1) nm, respectively, in support of the Mössbauer core-shell model. [ABSTRACT FROM AUTHOR]

In this study the synthesis of very small magnetite nanoparticles is reported. Analysis of the (311) X-ray diffraction line indicates nanoparticle with 2.2 nm average diameter. The as-synthesized nanosized magnetite sample was submitted to a chemical oxidation process for conversion to maghemite. However, the yielding of the chemical oxidation process, as indicated by the analysis of the Mössbauer data, was about 20%. This finding indicates a strong size-dependence of the oxidation process, reducing the yielding of the chemical process used as the nanoparticle size reduces down to extremely low values. [ABSTRACT FROM AUTHOR]

We report the structural characterization of Gd5Ge2(Si1 − xSnx)2 (x = 0.23 and x = 0.40) compounds by means of 100 and 298 K-X-ray diffractometry (XRD) and 4 K-155Gd and 298 K-119Sn Mössbauer spectroscopy. These compounds order ferromagnetically at 218.4 and 172.7 K, respectively. At ∼100 K, it was identified the Gd5Si4-orthorhombic phase (type I) for both samples. At ∼298 K, it was identified a Gd5Si2Ge2-monoclinic phase, for x = 0.23 and a Sm5Sn4-orthorhombic phase (type II), for x = 0.40. The Rietveld analysis of XRD data suggests a first order magneto-structural transition at Curie temperature for both compositions. Mössbauer results are well consistent with the proposed crystallographic models for these systems. [ABSTRACT FROM AUTHOR]

The Mössbauer spectra of Y3Al xCr XFe5 − 2 xO12 ( x = 0.0 to 0.6) measured at 300 K have been fitted with two sextets in the ferrimagnetic state corresponding to Fe3+ at the octahedral (a) and the tetrahedral (d) sites for x ≤ 0.6. The isomer shifts (δ) and quadrupole splitting (ΔEQ) indicate the presence of high spin Fe3+ ions in the tetrahedral (d) and octahedral (a) sites, typical of yttrium of yttrium iron garnet structure. Mössbauer results have shown that Al3+, enters a-sites only but Cr3+ enters both a-and d-sites. [ABSTRACT FROM AUTHOR]

Three volcanic dykes, rhyolite, dacite and trachyandesite cutting a radioactive granite, located between Latitudes 22° 47′ 396″–22° 47′ 884″ N and Longitudes 31° 54′ 883″–31° 54′ 894″ E in the south Western Desert of Egypt were sampled and analyzed by X-ray diffraction, 57Fe Mössbauer spectroscopy and chemical method. They are consisted of feldspar and quartz together with some paramagnetic minerals including aegirine plus minor riebeckite in the rhyolite; aegirine plus some riebeckite in the dacite; and riebeckite plus trace aegirine in the trachyandesite, respectively. The bulk content of iron in each dyke has characteristic ferric-quadrupole splitting and oxidation values: 0.29 millimeters per second (mm/s) and 100% for rhyolite; 0.31 mm/s and 82% for dacite; and 0.35 mm/s and 0.69% for trachyandesite. Variations in the quadrupole splitting have been attributed to changes from the local crystal chemistry, while the oxidation variations are source-related. [ABSTRACT FROM AUTHOR]

Samples of SnO2 doped with different amount of Fe (10–20%) and Sb (5–25%) were prepared by sol–gel method. Room temperature ferromagnetism was found to increase as a result of co-doping with Sb, as compared to SnO2 doped only with Fe. 57Fe Mössbauer spectra of almost all samples exhibited two paramagnetic doublets and a small subspectrum referring to magnetic relaxation at room temperature. Only the samples Sn0.65Fe0.2Sb0.15O2 − δ and Sn0.85Fe0.1Sb0.05O2 − δ with 4 h long annealing time showed well developed sextets and larger magnetic coercivity compared to that of the other samples. The sextet observed was considered to be due to precipitates like Sn doped α-Fe2O3. The results suggest that the origin of the magnetic interactions is enhanced by the presence of magnetic defects, which can interact with the iron ions by free carrier electrons. For the sample with precipitates, the grain boundary defects may play an important role of enhanced ferromagnetism. [ABSTRACT FROM AUTHOR]

Co-milling of AlO(OH) xerogels with various iron(III) compounds such as α-Fe2O3 or K3[Fe(CN)6] has been used for mechanochemical activation leading to Fe/Al oxide phases in coexistence with the activated main component. The results obtained allow a deeper insight into the chemical processes occurring during activation, doping, and thermal treatment in atmospheres of different chemical activity (H2O; N2; O2/N2; H2/N2). Evidence will be given for Fe3 + species being able to form suitable crystallization germs and to lower the crystallization temperature. One can distinguish between the incorporation of Fe3 + ions into the alumina matrix at the crystallite growth (e.g. on Fe2O3-like seeds) and the incorporation of Fe3 + ions during the last steps of crystallization. These last-mentioned Fe3 + ions are provided by coexisting Fe/Al oxide phases. In contrast to alumina matrices equilibrated at high temperatures (e.g. at 1,200–1,500°C), the matrices formed in situ are able to incorporate Fe3 + ions by diffusion at temperatures of ∼900–1,100°C in a short time regime. [ABSTRACT FROM AUTHOR]

There is a general lack of understanding of the hydrogen isotope fractionations between different experimental approaches both at higher and at lower temperatures of exchange. The complexity of bonding related with the hydroxyl ion in most hydrous minerals makes theoretical treatments rather difficult. Though some of the differences between experimental findings have recently been shown to be related to pressure effects that influence the hydrogen isotope fractionation properties of water, some other factors may also have significance. One of the major unknowns is the compositional control, especially the Fe-content and effects of variable Fe3+/Fe2+ ratios on hydrogen isotope fractionations between minerals and fluids (Suzuoki and Epstein, Geochim Cosmochim Acta 40:1229–1240, ; Chacko et al. ). We have studied a series of amphibole samples by Mössbauer spectroscopy, EPMA and TC-EA-IRMS to examine for possible correlations between D/H fractionation and Fe2+ to Fe3+ ratio/total iron content. Our measurements show that this correlation may exist for one particular origin of samples, but local conditions of mineral formation (most probably chemical composition and reactions accompanying the formation of minerals) may be more important in controlling the hydrogen isotope composition of minerals. [ABSTRACT FROM AUTHOR]

Low temperature 57Fe Mössbauer spectra of mechanically alloyed EuFeO3 prepared by mechanical alloying depicts an interesting transformation in its hyperfine magnetic state, from a triple phase magnetic system at room temperature to a single phase ferromagnetic state at 20 K. The hyperfine magnetic field increased by 12% at 20 K from its room temperature. The isomer shift and quadrupole splitting values exhibit a peak around 200 K. Low temperature 151Eu Mössbauer measurements show that the line-width increased to its maximum value at 80 K which is 45% compared to its room temperature value not enough to suggest splitting. [ABSTRACT FROM AUTHOR]

Mössbauer spectra acquired by the Mars Exploration Rovers (MERs) often have low statistics with overlapped component spectra, making it difficult to fit individual spectra for all hyperfine or other parameters. When a set of spectra is complementary in the sense that components are weak in one and strong in another, analyzing the spectra simultaneously (simfitting them) while equating or relating parameters among the spectra will reduce parameter correlations and can lead to convergence of otherwise unfittable spectra. We apply an author-written Windows-based Mössbauer data fitting program to three cases from the MER data set to demonstrate the capabilities and advantages of the simfit method. [ABSTRACT FROM AUTHOR]

A new experimental setup and methodology that allows the automatic tracking of a Mössbauer absorption line as its energy position varies during the experiment is introduced. As a test the sixth spectral line of FeSn2 was tracked while temperature was varied between room temperature and a value slightly above its Néel temperature. [ABSTRACT FROM AUTHOR]

Low temperature 57Fe Mössbauer spectra of mechanically alloyed EuFeO3 prepared by mechanical alloying depicts an interesting transformation in its hyperfine magnetic state, from a triple phase magnetic system at room temperature to a single phase ferromagnetic state at 20 K. The hyperfine magnetic field increased by 12% at 20 K from its room temperature. The isomer shift and quadrupole splitting values exhibit a peak around 200 K. Low temperature 151Eu Mössbauer measurements show that the line-width increased to its maximum value at 80 K which is 45% compared to its room temperature value not enough to suggest splitting. [ABSTRACT FROM AUTHOR]

Mössbauer investigations were carried out at room temperature on the ferrite system Li0.6 + 0.5tFe2.3 − 1.5tTitSb0.1O4 (0.0 ≤ t ≤ 1.0 in steps of 0.2). The effect of Ti4 + concentration on the various hyperfine interactions like Isomer shift, quadrupole splitting and internal magnetic field have been studied. The spectra exhibited well-defined Zeeman sextets at low substitution level, corresponding to the A and B sites. The sample with t = 1.0 showed paramagnetic behaviour. The results obtained have been discussed. [ABSTRACT FROM AUTHOR]

A sample of an ordinary chondrite fall, Didwana-Rajod, Rajasthan, India which was shown to be largely unweathered, was exposed to weathering in laboratory conditions. Wet and dry cycle of different strengths (0.01 and 0.1 M) of sodium sulfate solution was applied for different periods of time (maximum of 140 days). An attempt was made to simulate meteorite weathering more or less analogous to environmental exposure in desert-like conditions. It is found that lower concentration of the attacking ions is more effective in weathering the meteorite. Kamacite is affected in early cycles of weathering more than any other mineral. The olivine to pyroxene ratio is much less affected. [ABSTRACT FROM AUTHOR]

Intermixing in Si/Fe/Si trilayer induced by 120 MeV Au ions has been studied. X-ray fluorescence provides information about the depth distribution of Fe atoms, while Mössbauer spectroscopy and XAFS provide information about the changes in the local structure. In the as-deposited film Fe layer is amorphous in nature with a significant Si content in it. Irradiation to a fluence of 1 ×1013 ions/cm2 results in formation of non-magnetic intermixed layer with its hyperfine parameter close to those of Fe0.5Si with CsCl structure. XAFS measurements under X-ray standing wave condition provide depth resolved structural information. [ABSTRACT FROM AUTHOR]

Purple acid phosphatase, ( PAP), is known to contain dinuclear Fe2 + 2, + 3 site with characteristic Fe + 3 ← Tyr ligand to metal charge transfer in coordination. Phthiocoloxime (3-methyl-2-hydroxy-1,4-naphthoquinone-1-oxime) ligand L, mimics (His/Tyr) ligation with controlled and unique charge transfers resulting in valence tautomeric coordination with mixed valent diiron site in model compound Fe-1: [μ-OH-Fe2 + 2, + 3 ( o-NQCH3ox) ( o-NSQCH3ox)2 (CAT) H2O]. Fe-2: [Fe + 3( o-NQCH3ox) ( p-NQCH3ox)2]2 a molecularly associated dimer of phthiocoloxime synthesized for comparison of charge transfer. 57Fe Mössbauer studies was used to quantitize unusual valences due to ligand in dimeric Fe-1 and Fe-2 complexes which are supported by EPR and SQUID studies. 57Fe Mössbauer spectra for Fe-1 at 300 K indicates the presence of two quadrupole split asymmetric doublets due to the differences in local coordination geometries of [Fe + 3]A and [Fe + 2]B sites. The hyperfine interaction parameters are δ A = 0.152, (Δ E Q)A = 0.598 mm/s with overlapping doublet at δ B = 0.410 and (Δ E Q)B = 0.468 mm/s. Due to molecular association tendency of ligand, dimer Fe-2 possesses 100% Fe + 3(h.s.) hexacoordinated configuration with isomer shift δ = 0.408 mm/s. Slightly distorted octahedral symmetry created by NQCH3ox ligand surrounding Fe + 3(h.s.) state generates small field gradient indicated by quadrupole split Δ E Q = 0.213 mm/s. Decrease of isomer shifts together with variation of quadrupole splits with temperature in Fe-1 dimer compared to Fe-2 is result of charge transfers in [Fe2 + 2, + 3 SQ] complexes. EPR spectrum of Fe-1 shows two strong signals at g 1 = 4.17 and g 2 = 2.01 indicative of S = 3/2 spin state with an intermediate spin of Fe + 3(h.s.) configuration. SQUID data of $\chi _m^{{\rm corr}} \mbox{.T}$ were best fitted by using HDVV spin pair model S = 2, 3/2 resulting in antiferromagnetic exchange ( J = −13.5 cm − 1 with an agreement factor of R = 1.89 × 10 − 5). The lower J value of antiferromagnetic exchange leads to Fe+3μ-(OH) Fe + 2 bridging in Fe-1 dimer instead of μ-oxo bridge. The intermolecular association through H-bonds may lead to weakly coupled antiferromagnetic interaction between two Fe-2 molecules having Fe + 3(h.s.) centers. Using S = 5/2, 5/2 spin pair model we obtained best-fitted parameters such as J = −12.4 cm − 1, g = 2.3 with R = 3.58 × 10 − 5. Synthetic strategy results in non-equivalent iron sites in Fe-1 dimer analogues to PAP enzyme hence its reconstitution results in pUC-19 DNA cleavage activity, as physiological functionality of APase. It is compared with nuclease activity of Fe-2 RAPase. [ABSTRACT FROM AUTHOR]

The abundances of FeII and FeIII environments within green rusts one, GR1s, that intercalate carbonate, oxalate and methanoate (formate) anions are found from Mössbauer spectra for compositions corresponding to [Fe $^{\rm II}_{6}$ Fe $^{\rm III}_{2}$ (OH)16]2 + •[CO $_{3}^{2-}$ •5H2O]2 − , [Fe $^{\rm II}_{4}$ Fe $^{\rm III}_{2}$ (OH)12]2 + •[CO $_{3}^{2-}$ •3H2O]2 − , [Fe $^{\rm II}_{6}$ Fe $^{\rm III}_{2}$ (OH)16]2 + •[C2O $_{4}^{2-}$ •4H2O]2 − and [Fe $^{\rm II}_{5}$ Fe $^{\rm III}_{2}$ (OH)14]2 + •[2HCOO − •3H2O]2 − . These formulae correspond to orders α, β and γ where cation distances are (2 × a 0), ( $\surd 3$ × a 0) or a mixture of both leading to (7 × a 0), where ratio x = {[FeIII]/[Fetotal]} = 1/4, 1/3 and 2/7, respectively. Anion distributions within interlayers are also devised and long-range orders determined accordingly. [ABSTRACT FROM AUTHOR]

Spinel ferrites have attracted a great deal of attention due to their application potential. These ferrites are attractive as well as from the theoretical point of view. Magnetic properties of the bulk materials differ drastically from the nano-sized materials. Often high temperature sintering is used to synthesize the nano-sized materials via solid state reaction route. This method yields bulk ferrites. For nano-sized materials low temperature sintering is required as basic requirement. Copper zinc ferrites have been synthesized by hydrothermal process which employs the decomposition of the hydroxides precursor at about 100°C. These samples were characterized by X-ray diffractometer (XRD), vibrating sample magnetometer (VSM),electron paramagnetic resonance (EPR) and Mössbauer spectroscopy. The average particle size in these sintered samples measured by XRD is found to vary from 10 to 150 nm. The XRD shows the formation of single phase spinel structure in all the samples. EPR gives the single asymmetric line at g ~ 2 with a line width of several hundred gauss. VSM displays non-saturating hysteresis loops and Mössbauer spectra show two sets of sextet related to two distinct sites of iron: site-A and site-B. [ABSTRACT FROM AUTHOR]

Nanocrystalline Fe3Mo3N, FeMoN2 and Ni3Mo3N interstitial nitrides having particle sizes of 32, 50 and 80 nm respectively, were synthesized by molybdate precursor route. The nanocrystalline nature was examined by XRD and SEM. Both, the field and temperature dependence of magnetic characteristics indicate paramagnetic behavior of the materials and the possible presence of magnetic contamination in the nitride materials. We examine the Mössbauer spectroscopic investigations in order to probe the magnetic characteristics and contaminations therein. X-ray photoelectron spectroscopy (XPS) study corroborates the possible presence of magnetic oxide phases at the surface of the Fe3Mo3N and Ni3Mo3N nano-particles. In summary, this paper investigates the magnetic properties of newer nitrides with appropriate corroboration with the Mössbauer and XPS studies. [ABSTRACT FROM AUTHOR]

Nd8Fe86 − x Nb x B6 ( x = 0, 1, 2, 3) nanocomposite magnet has been studied by Mössbauer spectroscopy and nanostructure observation. It was found that intergranular phase formed between α-Fe and Nd2Fe14B phase in NdFeNbB alloys plays a significant role on the magnetic properties. By the addition of Nb into Nd8Fe86B6 composition, coercivity was found to increase by 25% due to the grain refinement of both the soft and hard magnetic phases which was decreased from 50 nm of virgin Nd8Fe86B6 to 25 nm in Nd8Fe85Nb1B6 alloys. The role of Nb addition was confirmed to stabilize the Nd2Fe14B lattice preventing from thermal vibration of the corresponding sites at where Fe atoms are substituted by Nb in the Nd2Fe14B lattice. The enhanced coercivity was originated from the exchange hardening of soft and amorphous phases surrounding the hard magnetic Nd2Fe14B crystal. [ABSTRACT FROM AUTHOR]

Mössbauer effect spectroscopy and thermal analysis techniques were applied to characterize polyaniline composites successfully synthesized by embedding Fe oxide nanoparticles (about 10–13 nm) in a polymeric matrix in the presence of dodecyl benzene sulfonic acid and HCl (dopant). Thermal techniques provided quantitative information on iron oxide content and on polyaniline stability and transformations. Mössbauer results indicated that for the whole studied composition range, 3.4 to 100 iron oxide wt.%, composites hold maghemite particles. A preliminary study of the conductivity of the nanocomposites was performed. The largest conductivity was observed for a 8 wt.% maghemite composite where all particles are magnetically unblocked at room temperature within the Mössbauer time window. [ABSTRACT FROM AUTHOR]