57Fe Mossbauer Effect Research Articles

Relationship between Quadrupole Splitting and Filling Ratio x in YbxFe4Sb12

In a previous paper, the authors studied two samples of YbxFe4Sb12 (#1 and #2) by the Fe Mossbauer effect; it was found that the quadrupole splitting (QS 1⁄4 eqQ=2) for YbxFe4Sb12 (#1) at each temperature was slightly less than that for YbxFe4Sb12 (#2), thereby leading the authors to conjecture that the filling ratio x of Yb atoms in YbxFe4Sb12 (#2) was smaller than x in YbxFe4Sb12 (#1). However, in more recent papers, Ikeno et al. concluded that the ferromagnetic-transition temperature TC decreased with increasing x. From the relationship of x versus TC, the filling ratios in YbxFe4Sb12 (#1) and YbxFe4Sb12 (#2) are estimated at x 0:89 and x & 0:92, respectively. This indicates that x in YbxFe4Sb12 (#2) is larger than x in YbxFe4Sb12 (#1). In this paper, we explain the causation of the fact that QS increases with increasing x, and obtain the value of x in YbxFe4Sb12 (#2). The electric-field gradient eq at the Fe site is expressed as follows:

Mössbauer effect study of the decagonal quasicrystal Al65Co15Cu20

The 57 Fe Mossbauer effect study at 5.0 K and in an external magnetic field of 9.0 Ton a high-quality stable decagonal quasicrystal Al 65 Co 15 Cu 19.9 Fe 0.1 is presented. It is shown that the iron atoms are located in two distinct classes of sites. The values of the principal component of the electric field gradient tensor and the asymmetry parameter at these sites are, respectively, -1.90(10)x10 21 V/m 2 , 0.97(15) and -3.95(12)×10 21 V/m 2 , 0.00(17).

Mossbauer Studies on Nanoparticles of Zinc Substituted Magnesium Ferrite

Nanoparticles of zinc substituted Mg-ferrite (Mg (1-x) Zn x Fe 2 O 4 , x = 0.70 and 0.85) with well-developed spinel phases have been prepared by standard co-precipitation method. Single-phase ferrite with a spinel structure began to form at a relatively lower temperature (∼200 °C). X-ray diffratometry and 57 Fe Mossbauer effect measurements were carried out to characterize Mg-Zn-ferrite nanoparticles. The particle sizes obtained from Sherrer equation lie in the range, 6.4 nm to 25.6 nm. Mossbauer measurements at room temperature and down to 20 K clearly indicate the presence of superparamagnetic particles in all the samples. Superparamagnetic relaxation was observed at room temperature even for larger particle size of the samples and this may be due to the weakening of A-B exchange interaction in ferrite lattice due to replacement of Fe 3+ ions in tetrahedral sites by Zn 2+ ions.

Catalytic decarboxylations of fatty acids in immature oil source rocks

Catalytic decarboxylations of fatty acids in immature oil source rock samples were examined in this study. The rock samples were obtained from seven oil fields in China. In order to clarify the effect of each mineral matter in the rock samples, both the Fe Mossbauer effect and the X-ray diffraction (XRD) were used to determine the relative content of each mineral in the rock samples, and the catalytic activities of several minerals like clays, carbonates and pyrite were determined. The Fe Mossbauer effect and the XRD studies show that clays are the main mineral components in the rock samples except for the samples from Biyang and Jianghan in which the main mineral component is ankerite. The other mineral components include calcite, plagioclase, quartz, feldspar, siderite, aragonite, pyrite, analcime, pyroxene and anhydrite. The studies of the catalytic decarboxylations of fatty acids suggest that carbonates and pyrite can make much greater contributions to the catalytic activities of the rock samples than clays. It is found that the overall catalytic activities of the rock samples are well related to the relative contents and the catalytic activities of clays, carbonates and pyrite in the rock samples.

Spin Reorientation Studies in Nd2Fe14-xSixB (0<x≤2)

Nd 2 Fe 1 4 - x Si x B (z = 0.25, 0.5, 0.75, 1.0, 1.5, 2.0) intermetallic compounds were investigated by magnetometry, 5 7 Fe Mossbauer effect, electric resistivity, and differential scanning calorimetry mainly in the vicinity of the spin reorientation temperature, T S R . The Curie temperature, T C , and T S R were determined for different compositions and the spin phase diagram was constructed. 5 7 Fe Mossbauer spectra showed noticeable changes in the reorientation region. For temperatures above the transition, the spectra were analysed using 6 Zeeman patterns associated with 6 inequivalent crystal sites in Nd 2 Fe 1 4 B according to site occupations (16k 1 :16k 2 :8j 1 :8j 2 :4c:4e)). In the transition region, 12 subspectra had to be incorporated in the analysis. Electric resistivity measurements showed a typical metallic behaviour with no anomalies in the magnetic transition region. Differential scanning calorimetry measurements revealed broad endothermic two stage peaks around T S R .

Analysis for Magnetization of Ce1-xRxFe2(R= Pr, Nd) Based on NMR Study

We have carried out 141 Pr and 143 Nd NMR measurements on Ce 1- x R x Fe 2 (R = Pr, Nd) at 1.4 K. The hyperfine fields of Pr and Nd remain nearly constant in the measured concentration ranges: 0.15 ≦ x ≦0.43 and 0.1 ≦ x ≦0.4 for Pr and Nd compounds, respectively. The hyperfine fields analysis combining with 57 Fe Mossbauer effect results give the magnetic moments of Pr and Nd in the compounds to be about 2.6 µ B and 2.8 µ B , respectively. The magnetizations of Ce 1- x R x Fe 2 are estimated and discussed.

Formula omitted] Mossbauer study on the spinel system Zn xCo 1− xFe 2− xAl xO 4

Based on 57 Fe Mossbauer effect studies conducted at 300 K, the magnetic properties of the spinel solid solution series Zn x Co 1− x Fe 2− x Al x O 4 have been investigated. The Mossbauer spectra for x=0.0 to 0.4 suggest the existence of two hyperfine fields, one due to the Fe 3+ octahedral ions (B-sites) and the other due to the Fe 3+ tetrahedral ions (A-sites), while for x=0.5 and 0.6 it shows relaxation effects and for x>0.6 it exhibits a paramagnetic quadrupole doublet. The results are explained on the basis of A–B and B–B supertransferred hyperfine interactions. The canted spin structure in the system is verified.

Dynamics of phase stability and magnetic order in magnetoresistiveLa0.83Sr0.17Mn0.9857Fe0.02O3

Two samples with the same nominal composition La{sub 0.83}Sr{sub 0.17}Mn{sub 0.98}{sup 57}Fe{sub 0.02}O{sub 3} were prepared in air and argon. Thermograviametric, structural, resistive, and magnetic measurements show that the air-made sample has slightly higher Mn{sup 4+}/Mn{sup 3+} ratio; i.e., it is slightly more highly doped by {approximately}0.15{percent} cation vacancies. Substitution of Fe for Mn depresses the ferromagnetic transition temperature T{sub c} but has very small effect on the rhombohedral/orthorhombic structural phase boundary. Dramatic differences are found in transport properties for small differences in Mn{sup 4+} concentration near a structural and magnetic phase boundary. The dynamics of charge hopping and exchange via the effect of relaxation of the magnetic hyperfine field distribution and its average value are monitored by temperature-dependent Mossbauer effect measurements. Ferromagnetic clustering is observed above T{sub c} at {sup 57}Fe sites. The compound undergoes complex temperature dependent magnetic and phase behaviors that are monitored locally by the {sup 57}Fe Mossbauer effect. The iron probe has a stable 3+ valance configuration whose hyperfine interaction reflects the structural phase changes, the Jahn-Teller distortion and the time-dependent Mn{sup 3+}-Mn{sup 4+} charge fluctuations. It is shown that regions of magnetic order exist over {approximately}100 K range beginning well above T{sub c}. Moreover,more » the low-temperature structural phase, reported to be orthorhombic at this composition, shows dynamic magnetic fluctuation behavior that motionally narrows at low temperature. Any changes in hyperfine interaction due to the structural transition are masked by the fluctuating magnetic behavior, but clearly the two structures coexist in the temperature region near T{sub c}. {copyright} {ital 1998} {ital The American Physical Society}« less

Mössbauer spectroscopy of ferrocene in a crystal G liquid crystal

Abstract The Fe-57 Mossbauer Effect (ME) was used to study a 0.6 per cent (by weight) solution of 1,1′-diacetylferrocene in the liquid crystalline material N-(p-n-pentyloxybenzylidene)-p-n-hexylaniline (50.6). The ME parameters were determined for the crystalline solid phase and the cold crystal G phase. Characteristic Debye temperatures, order parameters, intramolecular and lattice contributions to the nuclear vibrational anisotropy were obtained for the crystalline solid, crystal G glass, and oriented crystal G glass phases.

Mössbauer studies of DNF and FMA in a smectic B liquid crystal

Abstract The FE-57 Mossbauer effect (ME) was used to study two solutions 0.4 wt% of ferrocenyl-4′-methoxyaniline (FMA) in the liquid crystalline material 4-n-butoxybenzylidene-4′-n-octylaniline (40.8) and 0.4 wt% of 1,1′-dinonanoyl-ferrocence in 40.8. The ME parameters were determined for the temperature range 40-300 K in the crystalline solid phase and 40–220 K in the cold smectic B phase of 40.8 for both samples. The ‘cold smectic B’ is defined as the smectic B glass and the supercooled smectic B phase. For T < 60 K the DNF-40.8 system exhibited a ME spectrum that was composed of two quadrupole split doublets. This four-line spectrum was observed for both the crystal phase and the smectic B glass phase of the DNF-40.8 system. The FMA-40.8 system exhibited a single quadrupole doublet. The In (recoil-free intensity f) versus T data exhibited linear Debye behaviour for the solid phase over the entire temperature range. The cold smectic In f versus T data also exhibited Debye behaviour for this system. The ...

High field magnetic investigations of the UFe10—xNixSi2 system

Abstract Magnetic measurements of UFe 10—x Ni x Si 2 were performed in magnetic fields up to 14 T at temperatures of 4.2–300 K. The values of the saturation moment amount to about 15 μ B /f.u. for UFe 8 Ni 2 Si 2 . The remanence increases with an increase in the Ni concentration, however, the saturation magnetization and the Curie point decrease, reaching p s = 2 μ B /f.u. and T c = 45 K , respectively, for UFeNi 9 Si 2 . The shape of the magnetization curves for x = 9, 8 and 6 suggests the possibility of the first order magnetization process (FOMP). The comparison of the results of the present investigation and that performed using the 57 Fe Mossbauer effect provides evidence of a substantial contribution of the uranium, and possibly the nickel, sublattices to magnetic ordering.

Magnetic properties and 57Fe Mössbauer effect in the substoichiometric Ln  Fe  (Re,Mo) systems with the ThMn12 structure

Abstract Magnetic properties and 57 Fe Mossbauer effect have been investigated in the following compounds: Ce 1.33 Fe 8.8 Mo 3.2 , Ce 1.33 Fe 10 Re 2 , Pr 1.64 Fe 7.2 Re 4.8 and Sm 1.8 Fe 7.5 Re 4.5 in the broad temperature range. All these compounds turned out to be ferromagnetic at low temperature; however, under an applied magnetic field of 5 T, saturation is not reached. The Curie points and saturation magnetic moments determined in both experiments are in fair agreement with previous results obtained on stoichiometric samples, except for the Pr compound. In all samples, an admixture of other phases was detected. The XRD patterns, however, do not give indication of their structure.

Characterization and pH stability of insoluble products of the reaction between cyanide and ferrous sulphate

X-ray diffraction (XRD), infrared (IR) spectroscopy and57Fe Mossbauer effect spectroscopy were used to characterize and monitor the pH stability of cyanide and ferrous sulphate reaction mixtures. Limited information was obtained from the XRD and IR measurements because of the amorphous nature of the samples. The Mossbauer studies show that considerable changes occur when there is an increase in pH at which the sample is prepared. Prussian-blue type compounds and iron oxide in the form of small particles crystallize out at low and high pH values, while additional complexes are formed at intermediate pH values of 6 to 9.57Fe Mossbauer effect spectroscopy is thus a powerful technique for monitoring the environmental stability of cyanide waste streams that result when modern methods of extractive metallurgy of gold are employed on mineral ores.

Rapid versus intermediate electronic relaxation between S = 3/2 and S = 1/2 states in nitrosyl-iron complexes with Jaeger-type ligands

The spin-state transitions between low-spin (S=1/2) and intermediate-spin (S=3/2) states in the complexes [Fe(J.ph)NO] and [Fe(J-mph)NO] with Jager-type ligands have been studied between 80 and 320 K on the basis of magnetism, 57 Fe Mossbauer effect, and X-ray powder diffraction. The transition in [Fe(J.ph)NO] is centered at T c ≃143 K, the electronic relaxation between the spin states being rapid with τ1≤10 -8 s at all temperatures

A Mössbauer Temperature Study of Ferrocenyl-4'-Methoxyaniline and Ferrocenyl-4'-n-Butylaniline in a Cold Smectic B Liquid Crystal

Abstract The Fe-57 Mossbauer effect (ME) was used to study two solutions 0.4% (by weight) of ferrocenyl-4'-methoxyaniline (FMA) in the liquid crystalline material 4-n-butoxybenzylidene-4'-n'-octylaniline (40.8) and 0.4% (by weight) of ferrocenyl-4'-n-butylaniline (FBA) in 40.8. The ME parameters were determined for the temperature range 110–170 K in the crystalline solid phase and 110–150 K in the cold smectic B phase of 40.8 for both samples. The ln recoil-free intensity (f) vs T data exhibited linear Debye behavior for the solid phase over the entire temperature range for both systems. The cold smectic ln f vs T data also exhibited Debye behavior, and the smectic glass gave a Mossbauer-Debye temperature (θLC) about 23 K lower than the crystalline phase for the FMA-40.8 system and about 30 K for the FBA-40.8 system. The smectic B glass yielded an order parameter of S = 0.28 for the FMA molecules at 110 K and S = 0.24 for FBA molecules at 110 K. The intermolecular contribution to the vibrational ellipsoid...

Pervasiveness of cluster excitations as seen in the Mössbauer spectra of magnetic materials

Magnetic cluster excitations in various physical systems (e.g., soliton bearing one-dimensional solids, metallic alloys, amorphous materials, small particle aggregates, magnetically ordered substances near TC, transition metal di-chloride graphite intercalation compounds, etc.) are described. Use of Fe-57 Mossbauer effect spectroscopy as a probe of the spin dynamics for inverse autocorrelation times between ∼107Hz to ∼1010 Hz is emphasized. Particular attention is given to systems which exhibit local or long range magnetic order and whose Mossbauer spectra must therefore be described by more than one autocorrelation (or dwell) time for fluctuations between different allowed hyperfine field directions on a given site.

Mössbauer study on the chemical state of iron in binary oxide glasses based on Fe 2O 3

Iron-containing binary oxide glasses in the systems of Fe 2 O 3 -P 2 O 5 , -TeO 2 , -SrO, -BaO, -PbO and -Bi 2 O 3 were prepared by using a twin-roller quenching method, and 57 Fe Mossbauer effect measurements were carried out on these glasses in order to determine the chemical state of iron ions. All the iron ions existed as Fe 3+ ions in all the glasses except Fe 2 O 3 -P 2 O 5 ones in which Fe 2+ ions coexisted. Fe 3+ ions in Fe 2 O 3 -P 2 O 5 and -TeO 2 glasses were laid on octahedral sites while they occupied tetrahedral sites in Fe 2 O 3 -SrO, -BaO, -PbO and -Bi 2 O 3 glasses. The covalency of Fe-O chemical bond was directly estimated from the isomer shift. The covalency was large in Fe 2 O 3 -SrO, -BaO, -PbO and Bi 2 O 3 glasses, while it was small in Fe 2 O 3 -P 2 O 5 and -TeO 2 glasses. This large dependence of the chemical state of iron ion on the kind of other cations coexisting with iron ions was explained based on the ionic character of chemical bonds between other cations and oxygen ions. Furthermore, the effect of covalency of Fe-O bonds on the magnetic properties of the glasses was discussed qualitatively.

Hyperfine interactions in stabilized Fe1−δO:Al3+ system

Highly stable Fe1−δO:Al3+ system has been synthesized by checking the spontaneous disproportionation of FeO. The novel preparation route of incorporating non-magnetic trivalent Al3+ ions in the wustite lattice is followed for the preparation of solid solutions. X-ray diffraction (XRD), chemical analysis and Fe57 Mossbauer effect are used for the characterization. The hyperfine interaction parameters reported are characteristic of high spin Fe2+ state which confirmed the stabilization of FeO.

An 57Fe Mossbauer effect study on glauconites from different locations in Belgium and Northern France

AbstractSixteen glauconite samples from different locations in Belgium and Northern France were investigated by 57Fe Mössbauer spectroscopy at room temperature. The spectra were fitted with three Fe3+ and two Fe2+ doublets, both Fe species occupying M1(trans) and M2(cis) sites in the T-O-T layers. The third Fe3+ doublet was assigned to interlayer ferric complexes. The observed Mössbauer parameters did not show significant variations from sample to sample. No direct relation between K and Fe content was observed, although within some distinct groups (e.g. Bande Noire, Cenomanian) the amount of Fe2+ increased with increasing K content.

An57Fe mössbauer effect study of ankerite

A natural sample of ankerite has been characterized by chemical analysis, X-ray diffraction and differential thermal analysis. The composition was found to be (Ca1.11Mg0.50Fe0.33Mn0.09) [Co3]1.99.57Fe Mossbauer effect measurements were performed at temperatures between 4.2 and 400 K. At low temperatures (T < 25 K) relaxation effects are clearly dominant. The temperature dependence of the center shift is remarkably well reproduced by a model based on the Debije approximation of the lattice vibrations. In contrast, the temperature dependence of the quadrupole splitting cannot be described by any reasonable crystal field model. It is argued that an orbit-lattice coupling might explain the observed quadrupole splittings. A spectrum recorded in an applied field of 6 T reveals a positive electric field gradient from which an orbital doublet ground state is concluded. Highly anisotropic field reductions are derived but cannot be quantitatively explained due to a lack of knowledge concerning the magnetic structure of ankerite. The line widths decrease significantly with increasing temperature which is only partly due to the decreasing Mossbauer fraction.