Mössbauer study of tektites

Room temperature ⁵⁷Fe Mössbauer spectroscopy has been used to investigate the structural and oxidation state of Fe in tektites from different strewn fields. Spectra have been analyzed in terms of two quadrupole splitting distributions corresponding to Fe^3?+? and Fe^2?+?. All tektites show similar distribution of quadrupole splitting. Each distribution has one peak. The Fe^2?+? sites show a narrow region of Mössbauer line shift (δ) and quadrupole splitting (ε), δ?= 1.02–1.10 mm/s and ε?= 0.85–1.00 mm/s relative to α-Fe. These values have been assigned to intermediate coordination between tetrahedral and octahedral. The Fe^3?+? sites show wider regions of hyperfine parameters: δ?= 0.25–0.45 mm/s and ε?= 0.65–0.90 mm/s. The Fe^3?+?/Fe^2?+? ratio was found to be 0.05–0.15.     

Mössbauer study of pyrrhotite

Mössbauer spectra of natural monoclinic pyrrhotite (Fe₇S₈) have been determined at 300, 77 and 4.2°K and interpreted using a least squares fit computer programme. The spectrum at 77°K was resolved into five components. Four have a finite hyperfine field and one has zero hyperfine field gradient. The parameters obtained from the fit agree with the model of vacancy ordering in Fe₇S₈ proposed by Bertaut.     

Mössbauer and EPR study of nitrosyl hemoglobin

Nitrosyl hemoglobin was prepared by bubbling fresh⁵⁷Fe-enriched rat hemoglobin with NO. S- and X-band EPR spectra at 77 K are typical for anS=1/2 system with an anisotropicg-tensor and exhibit hyperfine interactions of¹⁴N with the electronic spin. Mössbauer spectra at 4.2 and 100 K consist of a superposition of spectra from high- and low-spin Fe(III), deoxygenated hemoglobin and a component corresponding toS=1/2,g=2, hyperfine constantsA _xx /g _{n n} =A _yy /g _{n n} =–19.6 T,A _zz /g _{n n} =6.8 T, quadrupole splitting E _Q=1.5 mm s^–1, isomer shiftI _s=0.42 mm s^–1 and linewidth 0.4 mm s^–1. The spin-lattice relaxation rate at 100 K is <2×10⁶ s^–1.     

Mössbauer study of Brazilian soapstone

Steatite mineral rocks, soapstone, have been studied by X-ray diffraction, optical microscopic analysis (modal analysis), electron probe micro analysis and Mössbauer spectroscopy for characterization, mineral percentages and chemical composition. Mössbauer spectra show both, magnetic interactions corresponding to magnetite and doublets corresponding to talc. chlorite, dolomite and tremolite. The temperature dependence of the quadrupole splitting in dolomite has been explained in terms of crystal field interaction.     

Mössbauer study of Slovak meteorites

⁵⁷Fe Mössbauer spectroscopy was used as an analytical tool in the investigation of iron containing compounds of two meteorites (Rumanová and Ko?ice) out of total of six which had fallen on Slovak territory. In the magnetic fraction of the iron bearing compounds in the Rumanová meteorite, maghemite, troilite and Fe-Ni alloy were identified. In the non-magnetic fraction silicate phases were found, such as olivine and pyroxene. The paramagnetic component containing Fe^3?+? ions corresponds probably to small superparamagnetic particles. The Ko?ice meteorite was found near the town of Ko?ice in February 2010. Its magnetic fraction consists of a Fe-Ni alloy with the Mössbauer parameters of the magnetic field corresponding to kamacite α-Fe(Ni, Co) and troilite. The non-magnetic part consists of Fe^2?+? phases such as olivine and pyroxene and traces of a Fe^3?+? phase. The main difference between these meteorites is their iron oxide content. These kinds of analyses can bring important knowledge about phases and compounds formed in extraterrestrial conditions, which have other features than their terrestrial analogues.     

Mössbauer study of Hungarian phlogopites

Ultramafic xenoliths of mantle origin occur in Hungarian Cretaceous lamprophyres. The aim of the present work was to determine the iron positions and their occupancy in phlogopites originated from ultramafic xenoliths by the help of Mössbauer spectroscopy. On the basis of the evaluation of the Mössbauer spectra Fe _M1 ²⁺ , Fe _M2 ²⁺ , Fe _M2 ³⁺ and Fe _M1 ³⁺ (or in some cases Fe_tet) octahedral and tetrahedral iron sites were identified in the samples. Quantitative analysis was performed for all of the iron sites. We have observed large differences between the Fe²⁺/Fe³⁺ ratio in samples originated from 120–150 km deepness, which phlogopites having been existed at different erosion circumstances. We have found a significantly higher Fe²⁺/Fe³⁺ ratio in phlogopites which had been solidified in 120–150 km depth from the surface of Earth 70–100 million years ago, than those had been crystallized in 60–80 km deepness.     

Mössbauer study of natural wolframites

Natural Wolframite, (Fe _x Mn_1?x )WO₄ withx=0.95 to 0.41, obtained from seven different sites of two quartz-wolframites deposits of Degana and Sirohi in Rajasthan. India, have been studied by Mössbauer spectroscopy down to 20 K. X-ray diffraction studies with a monochromatic Cu radiation (λK_a-1.5405 Å), were carried out to determine the value ofx. The Mössbauer spectra of all seven samples were recored at 300, 200, 100, 50, 40, 30 and 20 K, and were least square fitted for different sites. The Mössbauer parameters are attributed to a high spin ferrous ion in a quite distorted octahedral symmetry, and only one sextet has been resolved below transition temperature.     

Mössbauer study of cubic FeGe

The cubic structure of FeGe has been examined in the temperature range 80 – 300°K. The isomer shift and the quadrupole splitting suggest a Fe³⁺ state. A magnetic transition was found slightly above 273°K.     

Mössbauer study of synthetic jarosites

The structure around the metal site of mavicyanin, a protein molecule with a copper site, was investigated in solution by using time-differential perturbed angular correlation of ¹¹⁷In. The electric field gradient (EFG) of the metal site was deduced from the measurement. It demonstrated that the site in a mutant-type mavicyanin, Thr15Ala-Mav, gives an EFG different from that in the wild-type mavicyanin does. The pH dependence of the EFG was also observed for both proteins.     

Mössbauer studies and magnetic properties of spinel lead ferrite

In the present communication, we have reported the synthesis of nanocrystalline lead ferrite (PbFe₂O₄) by citrate mediated autocombustion method. X-ray diffraction pattern reveals the single phase formation in cubic (spinel) structure. The particle size and the surface morphology of the samples are characterized by TEM and SEM analysis. Magnetic studies are carried out using vibrating sample magnetometer (VSM) shows a very high coercive field for the material. Mössbauer studies were performed to investigate the local symmetry i.e. Fe is in octahedral/tetrahedral site and the charge states of Fe ions.     

Magnetic and Mössbauer properties of Fe doped VN nanoparticles

Nanoparticles of iron doped vanadium nitride are synthesized by simultaneous thermal decomposition and nitridation of [V_(1???x)Fe _x O(NH₂O)₂Gly]·H₂O in NH₃ atmosphere at 973 K for 4 h. Pure VN shows cubic NaCl structure with lattice parameter of a?=?4.126 Å. Lattice parameter increases with Fe-doping. Magnetization increases with increase of Fe amount in VN. Coercivity values are in the range 30–80 Oe, which is relatively so small, compared to pure Fe. From Mössbauer study, it is inferred that single resonance line is due to the high diamagnetic contribution and doublet peaks are due to the paramagnetic contribution, which is assigned to the presence of ζ-Fe₂N phase.     

Mössbauer study of anhydrous ferrous formate

α-Fe(HCO₂)₂, obtained by dehydration of Fe(HCO₂)₂. 2H₂O was studied by Mössbauer spectroscopy. As expected, a single environmental iron site was found, displaying a Q.S. of (1.86 ±0.03) mm/sec, midway between the two iron splittings in Fe(HCO₂)₂.2H₂O, whereas the I.S. remained almost unchanged. Measurements between 300 and 77°K show a line width increase of 20%.     

Mössbauer study of natural iron-oxide complexes

Hyperfine Interactions - Typical Fe-oxide complex assemblage in rock samples taken from Lake Victoria Goldfield in Tanzania was studied using Mössbauer spectroscopy between room temperature...     

Mössbauer study of iron-doped lithium niobate

From Mössbauer spectra of LiNbO₃⁵⁷Fe(III) single crystals under external fields of 4.92 and 6.2 T, the crystal field and hyperfine parameters are determined. Transmission integral fits indicate a Boltzmann population of the Fe(III) electronic levels with a spin temperature equal to the sample temperature. Spectra at external fields of 0 T and 19 mT can be satisfactorily simulated using an effective spin 1/2,g-factors calculated from spin-expectation values and an internal averaged dipole field of 5.5 mT inclined 20 to thec-axis. The simulations indicate cross-relaxation between Nb and Li nuclear spins and the Fe(III) electronic spin.     

Mössbauer and XRD study of hot dip galvanized alloy

Mössbauer spectroscopy has been used to investigate the nature of the Zinc-Iron alloys present within the Hot Dip Galvanized (HDG) layers of steel with a silicon content of 0.35 %. The investigation also studied the impact of the powder coating pretreatment on the nature of the alloy layers. The acid etching process within the pretreatment process in particular would be expected to have a significant impact on the HDG layer. This study utilized ⁵⁷Fe Mössbauer spectroscopy to examine identically processed samples prior to and post pre treatment. XRD and ⁵⁷Fe CEMS measurements were performed on hot galvanized S355J2 + N samples, forming sandwiched structure. Both XRD and CEMS reveal the presence of dominant steel phase in accordance with its estimated occurrence on the surface of the sandwiched samples. Minor Γ-Fe3Zn10, ζ-FeZn15 and solid solution Fe-Zn as well as minor Fe-Si phases could also be identified.     

Mössbauer study of EUROFER and VVER steel reactor materials

⁵⁷Fe Mössbauer spectroscopy and X-ray diffractometry were used to study EUROFER or VVER ferritic reactor steels mechanically alloyed with TaC or NbC. Significant changes were found in the Mössbauer spectra and in the corresponding hyperfine field distributions between the ball milled pure steel and that alloyed with TaC or NbC. Spectral differences were also found in the case of use of same carbides with different origin, too. The observed spectral changes as an effect of ball milling of the reactor material steels with carbides can be associated with change in short range order of the constituents of steel.     

Mössbauer and XRD study of intercalated CaFe-layered double hydroxides

N-containing fully saturated (L-prolinate) or aromatic (indole-2-carboxylate) heterocyclic anions were immobilised in CaFe-layered double hydroxide with the dehydration-rehydration method from aqueous ethanol or acetone. The structure of the resulting organic-inorganic hybrids was characterised mainly with powder X-ray diffraction and ⁵⁷Fe Mössbauer spectroscopy, and as supplementary analysis scanning electron microscopy, energy dispersive X-ray spectroscopy with elemental mapping and molecular modelling were also applied. It was found that the solvent mixture used for the synthesis caused enormous difference in the interlayer spacings of the obtained inorganic-organic hybrids.     

Mössbauer spectroscopic properties of tin-doped iron oxides

The ⁵⁷Fe Mössbauer spectra recorded in situ from tin-doped Fe₃O₄ at elevated temperature in vacuo shows the Curie temperature to decrease with increasing concentrations of the dopant. Thermal treatment under oxidising conditions results in the initial formation of tin-doped γ-Fe₂O₃ which subsequently undergoes a phase transformation to tin-doped α-Fe₂O₃. ⁵⁷Fe Mössbauer spectroscopy at elevated temperatures shows the Néel temperature for tin-doped γ-Fe₂O₃ to be lower than that of pure γ-Fe₂O₃. The ¹¹⁹Sn Mössbauer spectra recorded from all the tin-doped iron oxides show the presence of a hyperfine magnetic field at the Sn⁴⁺ site which is more complex in the spectra recorded from tin-doped γ-Fe₂O₃ and α-Fe₂O₃.