Mössbauer Spectroscopy in the Characterisation of Polymetallic Cluster Compounds: a Triple Mössbauer Study of (PPh4)[Fe2Ir2(CO)12{μ3-Au(PPh3)}]

The iron meteorites Sikhote–Alin, Bilibino, Chinga and Dronino with different Ni concentration and terrestrial age were studied by Mössbauer spectroscopy. Different Mössbauer hyperfine parameters were determined for studied meteorites and possible Fe–Ni phases were supposed.     

Application of the Mössbauer effect to the study of meteorites—A review

Mössbauer and X-ray diffraction studies revealed that segregation and ordering of Fe?Ni alloys occurs in meteorites in close resemblance with irradiation effects in these alloys. In Santa Catharina (35% Ni) and Twin City (30% Ni) ataxites, the ordering mechanism leads to the formation of rather large amounts of the 50–50 Fe?Ni ordered phase with tetragonal symmetry (tetrataenite). Furthermore this ordered phase has also been detected in metal particles of chondrites.     

Investigations of Al-Dalang and Al-Hawashat meteorites

Mössbauer spectroscopy, X-ray diffraction (XRD) measurements, and electron microprobe analysis (EMPA) have been performed on two meteorites named Al-Dalang and Al-Hawashat after identifying their falling sites in the Western region of Sudan. These two meteorites are ordinary chondrites with similar mineralogy. XRD and EMPA show that the two specimens consist of primary olivine, ortho-pyroxene and later crystallising clino-pyroxene as reaction rims against plagioclase. Fe-metal phases are dominated by kamacite (≈6 wt.% Ni) and minor amounts of tetrataenite (≈52 wt.% Ni). Troilite (FeS) and alabandite (MnS) are optically observed as sulphide phases. The Mössbauer measurements at 295 and 78 K are in agreement with the above characterizations, showing at least two paramagnetic doublets which are assigned to olivine and pyroxene and magnetic sextets assigned to kamacite (hyperfine field ≈33.5 T) and troilite FeS (hyperfine field ≈31 T).     

Comparative study of Aliskerovo,Anyujskij, Sikhote-Alin and Sterlitamak iron meteorites using Mössbauer spectroscopy

A comparative study of Sikhote-Alin IIAB, Anyujskij IIAB, Aliskerovo IIIE-an and Sterlitamak IIIAB iron meteorites was carried out using Mössbauer spectroscopy with a high velocity resolution as well as using metallography, scanning electron microscopy with energy dispersive spectroscopy and X-ray diffraction. Different numbers of spectral components were found in the Mössbauer spectra of Sikhote-Alin IIAB and Anyujskij IIAB and in the spectra of Aliskerovo IIIE-an and Sterlitamak IIIAB iron meteorites. The values of hyperfine field at the ⁵⁷Fe nuclei obtained for spectral components were related to α-Fe(Ni, Co), α ₂-Fe(Ni, Co) and γ-Fe(Ni, Co) phases with variations in Ni concentration.     

Preferential occupation of pyroxene sites by iron in diogenite meteorites

Three diogenite meteorites ALHA77256-121, Tatahounie and Bilanga are studied using Mössbauer spectroscopy to look at the iron occupancy in the two inequivalent pyroxene sites. Though the three meteorites belong to three different conditions, one is an Antarctica find, one is 75 years old fall and one is a recent fall, the iron occupancy in pyroxene sites is very similar. Fe^2?+? occupies only the less distorted site and hence a single sharp doublet is observed in the Mössbauer spectra of all these samples. In contrast eucrites show a distribution of iron ions in the two sites of pyroxenes.     

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.     

A study of laser surface alloyed steel

Coatings composed of Ni and Co based alloys were prepared by surface alloying of steel substrate. In the study of composition and structure of the coatings, Mössbauer spectroscopy in scattering geometry, X-ray diffraction and energy dispersive X-ray microanalysis were applied. The results, in addition to phase composition data, showed the effect of the thermal history of samples. The contribution of Mössbauer spectroscopy consists in revealing the structure details resulting from rapid cooling of the remelted surface layer.     

Study of visually different areas in the Chinga iron meteorite fragment using Mössbauer spectroscopy with a high velocity resolution

Visually different areas on the saw-cut surface of Chinga metal meteorite fragment were observed. Study of metal samples from these areas was carried out using scanning electron microscopy, X-ray diffraction and Mössbauer spectroscopy with a high velocity resolution. The obtained differences in Mössbauer parameters may be related to the differences in the microstructural Fe–Ni phase composition.     

Mössbauer spectroscopy study of iron oxide nanoparticles obtained by spray pyrolysis

Mössbauer spectroscopy was used in this study to investigate magnetite nanoparticles, obtained by spray pyrolysis and thermal treatment under H₂ reduction atmosphere. Room temperature XRD data indicate the formation of magnetite phase and a second phase (metallic iron) which amount increases as the time of reduction under H₂ is increased. While room temperature Mössbauer data confirm the formation of the cubic phase of magnetite and the occurrence of metallic iron phase, the more complex features of 77 K-Mössbauer spectra suggest the occurrence of electronic localization favored by the different crystalline phase of magnetite at low temperatures which transition to the lower symmetry structure should occur at T ～120 K (Verwey transition).     

High Oxygen Pressures and the Improvement of the M n+ -O Chemical Bond Through the Stabilization of the Highest Oxidation States (n+)

An evolution of local structure of Ni and chemical bonding, Ni(III)-O in perovskite lattice with strongly distorted structure is investigated with 57 Fe Mössbauer spectroscopy. The Mössbauer spectra for 57 Fe-doped TlNiO 3 were resolved to two quadrupole doublets with different isomer shifts, which underlines a partial charge disproportionation phenomenon: 2Fe 3+ M Fe 3+ f +Fe 3 m f . This result supports the existence of two different crystallographic sites for Ni in the distorted perovskite lattice.     

Study of iron meteorite Sikhote–Alin and extracted iron–nickel phosphides using Mössbauer spectroscopy with high velocity resolution

Comparative study of schreibersite and rhabdite extracted from Sikhote–Alin (IIAB) iron meteorite using Mössbauer spectroscopy, X-ray diffraction and magnetic measurements was carried out. Mössbauer spectra of bulk meteorite sample and extracted phosphides were recorded in 4,096 channels and then presented in 1,024 channels. Differences of the unit cell structure, the Fe, Ni and Co content, the room temperature Mössbauer spectra and Curie temperature for rhabdite and schreibersite were found.     

Mössbauer study of the NingQiang carbonaceous meteorites

The NingQiang carbonaceous meteorites from the Shan Xi(China) was falling in 1983. In this report, the Mössbauer spectra has been measured for the NingQiang meteorites and the spectra were analysed with computer. The experimental results indentify it as a carbonaceous meteorite of type III. The spectrum shows the principal iron components to be of olivine, magnetite, troilite and phyllosilicate or goethite material. For comparation the Mössbauer spectra of the Allende and Leoville carbonaceous meteorites have been also measured.     

Magnetically coupled clusters in aggregated maghemite ferrofluid: Mössbauer and magnetization study

Mössbauer spectroscopy in a weak static magnetic field and measurements of isothermal magnetization loops were used to study the effect of polymer coating of the γ-Fe ₂ O ₃ nanoparticles on the magnetic properties of concentrated ensembles of such nanoparticles. It was found that the individual coating of the nanoparticles by a ～ 1 nm layer of the polymer leads to the observable changes in the shapes of the Mössbauer spectra and the magnetization curves of the ensembles. Modeling of the experimental magnetization curves in the classical Langevin model and analysis of the Mössbauer spectra in the generalized multi-level relaxation model revealed that the establishment of interparticle magnetic dipole interactions leads to both a ～ 30 % increase in the magnetic anisotropy constant and a ～ 35 % increase in the width of the hysteresis loop.     

Study of metal grains extracted from chondrite Tsarev L5 using Mössbauer spectroscopy with high velocity resolution

Study of metal grains extracted from ordinary chondrite Tsarev L5 using Mössbauer spectroscopy with high velocity resolution was made for the first time. Three magnetic and one paramagnetic components were revealed in Mössbauer spectrum of extracted metal. These components were related to correspondent phases of Fe–Ni–Co alloy while only two magnetic components related to metal were revealed in the spectrum of bulk meteorite sample. The results obtained were in agreement with metallographic study of metal grains in meteorite Tsarev L5 which demonstrated the presence of four Fe(Ni, Co) phases.     

Mössbauer,X-rays and SEM analysis of meteorites from the mineralogy museum of the University of Parma (Italy)

Five meteorites, belonging to the private collection of the Mineralogy Museum of the University of Parma have been analyzed by Mössbauer spectroscopy, X-rays diffraction X-rays fluorescence and by scanning electron microscope. Following standard classification they have been assigned to the ordinary chondrites class, L type, with different minor compositions.     

Mössbauer spectroscopy of disordered magnetic systems

In the given summarizing article, we present the most important aspects of the technique of studying disordered magnetic systems by the Mössbauer effect being developed by us for the broad circle of researchers in magnetism and Mössbauer spectroscopy. The potentialities of this technique in investigating local magnetic characteristics and spin structures of disordered magnetics are assessed by the interpretation of Mössbauer spectroscopy data of various classes of well-studied magnetics (Fe?Al, Fe-V). In the concluding part, we present original results of Mössbauer investigations of binary (Fe?Cr, Fe?Pd and Fe?Au) and quasi-binary (Fe?Pd?Au) alloys characterized by non-trivial macroscopic magnetic properties and complex magnetic phase diagrams.     

Mössbauer effect study of Ni bearing aluminous goethites

Five synthetic oxyhydroxides of iron with different contents of Al and an approximately fixed content of Ni have been studied using⁵⁷Fe Mössbauer spectroscopy in conjunction with X-ray diffraction, infrared spectroscopy, transmission electron microscopy and chemical analysis. It has been shown that, besides alumogoethite, some amorphous Al-bearing phase of iron exists, Ni being preferentially associated with this phase. Not only the effective magnetic field, but also the line width of the Mössbauer spectra at 77 K may be a measure of Al content in both phases. Doublet to sextet area ratio provides a measure of the relative concentration of the amorphous and crystalline phases.     

Mössbauer spectroscopy of an ordered phase (superstructure) of FeNi in an iron meteorite

Mössbauer and X-ray spectra for taenite lamellae from the iron meteorite Cape York show that the lamellae contain an ordered phase with the composition FeNi, and with the structure L10. This phase has not previously been detected in meteorites.     

Local magnetic moments in crystalline and amorphous alloys

Hyperfine Interactions - Recent57Fe and61Ni Mössbauer spectroscopy studies of Fe and Ni magnetic moments in crystalline and amorphous alloys, as well as X-ray photoelectron spectroscopy...     

A study of the sump beaver's dental enamel

The nature of the iron-containing phase in the dental enamel of sump beaver incisors has been studied by use of Mössbauer spectroscopy. All iron atoms are found to be trivalent and to be present in particles exhibiting superparamagnetic relaxation. The iron-containing phase has Mössbauer parameters similar to those of ferritin.