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1.
The detailed temperature variation of the Mössbauer spectral intensity in Sn(CH3)4 displays a pronounced drop of the Debye temperature from
D
96K below the transition temperature (T
t
43K) to
D
76K above it. The transition atT
t
is discussed in terms of recent INS and NMR results where increased motion of inequivalent CH3 groups has been observed around the temperatureT
t
.Supported by the U.S.-Israel Binational Science Foundation 相似文献
2.
Mössbauer spectroscopy and XRD were employed to characterize the microstructural properties of iron-zinc binary alloys between 0–31 at.% Fe. Samples were prepared with accuracies of ±0.5 at.% Fe, and the Mössbauer and lattice parameters were monitored as a function of iron concentration across each phase. Two iron sites were observed in the phase (18–31 at.% Fe), whose occupancies and isomer shifts varied continuously with iron content. However, the quadrupole splitting of each site remained constant. Within the 1 phase (19–24 at.% Fe), three iron sites were observed whose isomer shifts and quadrupole splittings remained constant, while their occupancies varied with iron concentration. For the first time, a third iron site was observed in the phase (8–13 at.% Fe), whose occupancy increases with iron content. Also, the site occupancies of the two other sites appear to remain constant, while other Mössbauer parameters vary continuously with iron content. Analysis of the phase (6–7 at.% Fe) showed the presence of one iron site, whose parameters were not observed to change due to the small variance in iron concentration. XRD studies indicate the lattice parameters across the and phases vary continuously with iron concentration. Moreover, a better understanding of these phases, as formed in galvanneal steel coatings, was obtained.Research supported by the International Lead Zinc Research Organization, Inc., Grant No. ZM-403 and Virginia's Center for Innovative Technology, Grant No. MAT-92-007-01. 相似文献
3.
Mónika Sipiczki Ernő Kuzmann István Pálinkó Zoltán Homonnay Pál Sipos Ákos Kukovecz Zoltán Kónya 《Hyperfine Interactions》2014,226(1-3):171-179
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. 相似文献
4.
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. 相似文献
5.
F. M. Hayashida D. Killick I. Shimada W. Häusler F. E. Wagner U. Wagner 《Hyperfine Interactions》2014,224(1-3):161-170
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. 相似文献
6.
E. Kuzmann L. Sziráki S. Stichleutner Z. Homonnay G. B. Lak M. El-Sharif C. U. Chisholm 《Hyperfine Interactions》2017,238(1):97
Constant current electrochemical deposition technique was used to obtain quaternary alloys of Sn-Fe-Co-Ni from a gluconate electrolyte, which to date have not been reported in the literature. For the characterization of electroplated alloys, 57Fe and 119Sn Conversion Electron Mössbauer Spectroscopy (CEMS), XRD and SEM/EDAX were used. XRD revealed the amorphous character of the novel Sn-Fe-Co-Ni electrodeposited alloys. 57Fe Mössbauer spectrum of quaternary deposit with composition of 37.0 at% Sn, 38.8 at% Fe, 16.8 at% Co and 7.4 at% Ni displayed a magnetically split sextet (B = 28.9T) with broad lines typical of iron bearing ferromagnetic amorphous alloys. Magnetically split 119Sn spectra reflecting a transferred hyperfine field (B = 2.3T) were also observed. New quaternary Sn-Fe-Co-Ni alloys were successfully prepared. 相似文献
7.
Low temperature Mössbauer spectra and magnetic ordering of lithiated ferric molybdate: Li2Fe2(MoO4)3
Powder x-ray diffraction, variable temperature magnetic susceptibility, and zero field Mössbauer spectroscopy measurements were used to characterize the new phase Li2Fe2 (MoO4)3. This material is obtained topochemically simply by the mixing of solutions of lithium iodide in acetonitrile with solid Fe2(MoO4)3 at ambient temperature. Li2Fe2(MoO4)3 possesses the high temperature orthorhombic ferric molybdate $$\begin{gathered} Fe_2 (MoO_4 )_3 + 2LiI\xrightarrow{{CH_3 CN}}Li_2 Fe_2 (MoO_4 )_3 + I_2 \hfill \\ (solid)(solution)(solid)(solution) \hfill \\ \end{gathered}$$ structure. Guinier photographs were completely indexed in space group Pnca. Magnetic hyperfine splitting of the zero field Mössbauer spectrum below 12.5 K indicates a three-dimensional magnetically ordered state which susceptibility results show to be weakly ferromagnetic owing to probable canting of antiferromagnetically coupled sublattices. 相似文献
8.
Z. Homonnay P. Á. Szilágyi A. Vértes E. Kuzmann V. K. Sharma G. Molnár A. Bousseksou J.-M. Grenèche A. Brausam R. Meier R. van Eldik 《Hyperfine Interactions》2008,182(1-3):77-86
The speciation of iron in aqueous solutions containing Fe3?+ and selected chelates such as EDTA, EDDA, CDTA and HEDTA has been studied using transmission 57Fe Mössbauer spectrometry in frozen solutions. The protonation of various complexes as well as binuclear complex formation could be detected as a function of pH. Autoreduction of Fe3?+? to Fe2?+? was observed in several cases. Reaction with hydrogen peroxide proved to be rather different for the four ligands, while the dihapto complex [XFe(η 2-O2)]3??? had surprisingly identical Mössbauer parameters for X = EDTA, CDTA or HEDTA. Paramagnetic spin relaxation observed in the Mössbauer spectra was found to be strongly influenced by the identity of the chelating ligand, despite the basically spin-spin origin of the phenomenon. 相似文献
9.
I. Presniakov V. Rusakov A. Sobolev A. Gapochka M. Matsnev A. A. Belik 《Hyperfine Interactions》2014,226(1-3):41-50
The present work reports results of the 57Fe Mössbauer measurements on AgFeO2 powder sample recorded at various temperatures including the points of both magnetic phase transitions. The 57Fe Mössbauer spectra of AgFeO2 measured in the paramagnetic range (T > T N1) consist of one quadrupole doublet with rather high quadrupole splitting of Δ300K = 0.66 ± 0.01 mm/s for Fe3+ ions. In order to predict the sign of electric field gradient (EFG) at 57Fe nuclei, we calculated the lattice contribution to the electric field gradient (EFG) at 57Fe nuclei, which emphasized the importance of the dipolar contributions, with resultant oxygen polarizabilities in the range of α O = 0.83 Å3, in agreement with the results obtained previously for other delafossite-like oxides. In the temperature range of T N2 < T < T N1, Mössbauer spectra gave clear evidence for the existence of a distribution of the hyperfine magnetic fields H hf at 57Fe nuclei. We present the results of a model fitting of the spectra based on an assumption of the cycloid magnetic structure of AgFeO2 at T < T N2. The obtained data were analysed in comparison with published data on Mössbauer studies of oxide multiferroics. 相似文献
10.
V. S. Pokatilov A. S. Sigov A. O. Konovalova 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(3):347-351
Pulse nuclear magnetic resonance (NMR) was applied in studying the effect of 57Fe isotope content in multiferroic BiFeO3 on the shape of NMR spectra at 4.2 K. Strong dependences of the NMR line shape on the isotope content and transverse relaxation time were found. Consideration of these effects on NMR line shape shows that there is an undisturbed (with no anharmonicity effect) space spin-modulated structure of the cycloid type in BiFeO3. The Mössbauer effect was also used to investigate the perovskite BiFeO3 at 650, 295, and 87 K. Experimental spectra allowed us to obtain the distribution of hyperfine fields, which was found to be consistent with studies of the NMR line shape. The local electronic and magnetic states of the iron ion were measured. 相似文献
11.
ö. Helgason H. P. Gunnlaugsson K. Jónsson S. Steinthórsson 《Hyperfine Interactions》1994,91(1):595-599
Mössbauer spectroscopy of basalt lava samples, exhibiting reversible thermal magnetization (J
s
-T) curves with Curie temperatures of about 840 K, has revealed considerable amounts of maghemite (-Fe2O3) in many samples. In view of the expected instability of maghemite at temperatures above 620 K, this reversibility came as a surprise. For further studies of the magnetization-temperature relationship of these minerals, we have constructed an elliptical radiation-heated furnace in which Mössbauer spectra can be acquired at temperatures between 300 and 900 K. Measurements at different temperatures have been obtained for two types of basalts, one in which the magnetic minerals are nearly pure magnetite and the other where the room temperature spectrum indicates a mixture of maghemite and magnetite. The two series show different features of the collapse of the internal magnetic hyperfine field, and the composition of minerals in the samples changes during the treatment, showing maghemite. 相似文献
12.
Mark Davidson 《Foundations of Physics》2017,47(3):327-354
The rigid recoil of a crystal is the accepted mechanism for the Mössbauer effect. It’s at odds with the special theory of relativity which does not allow perfectly rigid bodies. The standard model of particle physics which includes QED should not allow any signals to be transmitted faster than the speed of light. If perturbation theory can be used, then the X-ray emitted in a Mössbauer decay must come from a single nuclear decay vertex at which the 4-momentum is exactly conserved in a Feynman diagram. Then the 4-momentum of the final state Mössbauer nucleus must be slightly off the mass shell. This off-shell behavior would be followed by subsequent diffusion of momentum throughout the crystal to bring the nucleus back onto the mass shell and the crystal to a final relaxed state in which it moves rigidly with the appropriate recoil velocity. This mechanism explains the Mössbauer effect at the microscopic level and reconciles it with relativity. Because off-mass-shell quantum mechanics is required, the on-mass-shell theories developed originally for the Mössbauer effect are inadequate. Another possibility is that that the recoil response involves a non-perturbative effect in the standard model which could allow for a non-local instantaneous momentum transfer between the crystal and the decay (or absorption), as proposed for example by Preparata and others in super-radiance theory. The recoil time of the crystal is probably not instantaneous, and if it could be measured, one could distinguish between various theories. An experiment is proposed in this paper to measure this time. The idea is to measure the total energy radiated due to bremsstrahlung from a charged Mössbauer crystal which has experienced a recoil. Using Larmor’s formula, along with corrections to it, allows one to design an experiment. The favored idea is to use many small nano-spheres of Mössbauer-active metals, whose outer surfaces are charged. The energy radiated then varies as the charge squared divided by the recoil time. This can then be measured with the extreme sensitivity available in Mössbauer experiments. If it turns out that experiments prove the need for off-mass-shell theory, then this would have profound implications for all of condensed matter physics. It would mean that an off-mass-shell theory like those considered by Stueckelberg, Horwitz, Piron, Greenberger, and many others are required to describe nature. The inclusion of these would be a major shift in the foundations. It would mean that there are new dynamic variables—the rest masses of particles. The ability to measure the diffusion relaxation time should prove useful also in chemical analysis, and provide a new class of analytical methods for material science. This problem is also interesting because the Mössbauer effect is a phenomenon where the solid-state environment dramatically and indisputably influences the probability of a nuclear process. 相似文献
13.
S. Stichleutner G. B. Lak E. Kuzmann C. U. Chisholm M. El-Sharif Z. Homonnay L. Sziráki 《Hyperfine Interactions》2014,226(1-3):15-25
Effect of pulse plating on novel electrodeposited binary and ternary amorphous alloys was studied by 57Fe and 119Sn conversion electron Mössbauer spectroscopy and X-ray diffraction. Our results show that by adjusting the parameters of pulse plating a fine tuning of the composition and current efficiency can be achieved within these systems. On the contrary to direct current deposition, where the crystalline FeSn2 phase dominates, pulse plating technique produces amorphous Sn-Fe alloy phases, of which the ferromagnetic phase is the dominant one. Both, direct current and pulse plated Sn-Ni deposits consist of paramagnetic alloy phases and minor amounts of β-Sn, the occurrence of which correlates with the tin content of the samples. Pulse plated Sn-Ni-Fe coatings are amorphous and in a dominantly ferromagnetic state, however at long on- and off-pulse times and high peak current density the paramagnetic state dominates and β-Sn segregation also occurs. 相似文献
14.
A brief overview of the contributions which Mössbauer effect spectroscopy has made to areas of materials science is presented. A survey of the literature reveals the decreasing trends of established areas, with emergence in the past decade or so of new areas such as nanostructured materials and materials produced by mechanochemical treatment and the continuing importance of rare-earth magnetic materials. Examples of applications of 57Fe and 119Sn Mössbauer spectroscopy, both transmission and backscattering, are discussed. The complementary nature of Mössbauer spectroscopy and neutron diffraction in delineation of the magnetic behaviour and structures of materials is demonstrated by the La1?x Y x Mn2Si2 series of rare-earth intermetallic compounds. 相似文献
15.
S. V. Stolyar O. A. Bayukov V. P. Ladygina R. S. Iskhakov L. A. Ishchenko V. Yu. Yakovchuk K. G. Dobretsov A. I. Pozdnyakov O. E. Piksina 《Physics of the Solid State》2011,53(1):100-104
Ferrihydrite nanoparticles formed as a result of the microorganism activity have been studied using Mössbauer spectroscopy, X-ray powder diffraction analysis, and X-ray fluorescence analysis. Three positions of trivalent iron with nonoverlapping ranges of quadrupole splittings have been revealed in bacterial ferrihydrite: QS{Fe3+(1)} = 0.49–0.83 mm/s, QS{Fe3+(2)} = 0.84–1.10 mm/s, and QS{Fe3+(3)} = 1.25–1.73 mm/s. It has been experimentally demonstrated that the Fe3+(3) positions are the centers of nucleation of the hematite phase in the course of heat treatment. 相似文献
16.
C. E. Johnson 《Hyperfine Interactions》1994,90(1):27-43
The Mössbauer effect enabled the magnetic hyperfine splitting (hfs) in ferromagnetic solids to be observed directly for the first time. It was quickly extended to measurements on antiferromagnets, ferrimagnets and paramagnets, and is now well established as a probe for the study of magnetic materials. Applications have ranged from the old problem of the state of the iron atoms in ferromagnetic alloys to the new magnetic materials, e.g. amorphous magnets, spin glasses, fine particle magnets and multilayers. Some examples where the Mössbauer effect has made an important contribution are described. 相似文献
17.
The peculiar properties of the Mössbauer effect provide an important test, and possibly a challenge, to Quantum Physics. The zero-point momentum reservoir of the mechanical oscillators forming a crystal lattice is indicated, in the present paper, as the possible way out from apparent contradictions of the observed features with both momentum conservation and the uncertainty principle. 相似文献
18.
The heat shock protein 70 (HSP70) in the chloroplast of Chlamydomonas reinhardtii, termed HSP70B, interacts with chloroplast-targeted DnaJ-like proteins (CDJs). In this work we focus on two CDJ co-chaperones (CDJ3 and CDJ4) of HSP70B which contain a redox-active Fe-S cluster (Dorn et al. Biochem. J. 427, 205 [2010]). We have performed Mössbauer spectroscopy on 57Fe enriched CDJ3 an) CDJ4. Our results indicate that both proteins have unusual [4Fe4S] 2+ clusters showing structural inhomogeneity of the two [Fe 2.5+-Fe 2.5+] pairs. The spectra have been analyzed by means of two components with δ-values characteristic for Fe 2.5+ centers, but the differences in ΔE Q indicate variations in their tetrahedral coordination spheres. 相似文献
19.
A. D. Al-Rawwas C. E. Johnson M. F. Thomas S. E. Dann M. T. Weiler 《Hyperfine Interactions》1994,93(1):1521-1529
Mössbauer spectra have been recorded at 4.2 and 300 K on the series La1–x
Sr
x
FeO3, wherex varies from 0 to 1.0 in steps of 0.1. Neutron diffraction experiments have shown that the crystal structure is orthorhombic for 0x<0.3, rhombohedral for 0.4x0.7, and cubic for 0.8<x1.0. Mössbauer spectra at 4.2 K are composed of magnetic sextet components arising from different charge states of iron ions. In the orthorhombic and rhombohedral phases, the charge states Fe3+ and Fe5+ coexist. In the cubic phase, iron is present as Fe3+ and Fe4+ states. At 300 K, the samples are magnetically ordered in the range 0 x0.3 and the coexistence of Fe3+ and Fe5+ remains. For samples 0.4x1.0, the samples are paramagnetic. Fits to these spectra require two components, one corresponding to an Fe4+ state, the other being best described as an Fe3+ ion forx0.7 but forx>0.7 having a mean charge state which increases to 3.5 forx=1.0. 相似文献
20.
M. L. Cubeiro F. González-Jiménez M. R. Goldwasser M. J. Pérez-Zurita E. Pietri L. García 《Hyperfine Interactions》2001,134(1):13-25
Iron-based catalysts have favorable activity and selectivity properties for the CO and CO2 hydrogenation reactions. Several Fe phases (oxides and carbides) can be present in these catalysts. The interaction of Fe
with the other components of the catalyst (support, promoters) can affect the ease of reduction and also its transformation
during the reactions. In this work, the relationship between catalytic behavior in the CO and CO2 hydrogenation reactions and the Fe phase composition of fresh and reacted catalysts was studied. Two types of catalysts were
tested: a laterite and the other one made of iron supported on alumina, both unpromoted and promoted with K and Mn. Only those
Fe species which can be reduced-carburized, by means of a pretreatment or by an in situ transformation under the reaction, seem to be able to perform the CO or CO2 hydrogenation. The reoxidation of the Fe carbide to magnetite was not associated to deactivation. The selectivity seems to
be more affected by Fe species difficult to reduce than by magnetite produced by reoxidation.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献