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Fe78B15Sn7 and (Fe3Co1)78B15Sn7 amorphous metallic alloys were prepared using the method of planar flow casting. The amorphous nature of ribbons containing 7 at. % Sn was verified by X-ray diffraction. The resulting chemical composition was checked by flame atomic absorption spectroscopy and by mass spectrometry with inductively coupled plasma. The microstructure of the as-quenched metallic glasses was investigated by 57-Fe and 119-Sn Mössbauer spectrometry. The experiments were performed with transmission geometry at 300 K, 100 K, and 4.2 K, and in an external magnetic field of 6 T. The replacement of a quarter of the Fe by Co did not cause significant modifications of the hyperfine interactions in the 57-Fe nuclei. The observed minor variations in the local magnetic microstructure were attributed to alterations in the topological short-range order. However, the in-field 57-Fe Mössbauer spectra indicated a misalignment of the partial magnetic moments. On the other hand, the presence of Co considerably affected the local magnetic microstructure of the 119-Sn nuclei. This was probably due to the higher magnetic moment of Co, which induces transfer fields and polarization effects on the diamagnetic Sn atoms. [ABSTRACT FROM AUTHOR]

In this work, we report the effect of Zn concentration on structural, magnetic and magnetocaloric properties of (0.75)La 0.62 Nd 0.05 Ba 0·33 MnO 3 /(0.25)Ni 1- x Zn x Fe 2 O 4 (x = 0.5, 0.6 and 0.7) nanocomposites. The samples with different compositions were synthesized by co-precipitation process. The XRD analysis confirms the presence of both phases namely perovskite La 0.62 Nd 0.05 Ba 0·33 MnO 3 and spinel NiZnFe 2 O 4 and further proved by TEM analysis. Room Mössbauer measurements get insights information about the effect of Zn content in the hyperfine parameters and magnetic transition. Magnetic measurements M(T) reveal the presence of a magnetic transition from paramagnetic (PM) to ferromagnetic (FM) phase in the vicinity of Curie temperature. With decreasing Zn concentration, the Curie temperature increases as well as the maximum entropy change. [ABSTRACT FROM AUTHOR]

High‐chromium steels are key alloys used for the construction of technological devices in industry. Stainless steels are suitable for components that are exposed to a corrosive environment for a long time because chromium has anticorrosion properties due to segregation of chromium and the formation of a passivation layer. The physicochemical properties of the surface and the bulk of the material as well are determined by microstructure. Herein, steel NS219 is focused on, where the chromium concentration is around 13.5 wt%. In order to study the microstructure of steel, Mössbauer spectroscopy is used. Experimental results are evaluated using the binomial distribution model of the probability distribution of atoms in the nearest neighbor of the resonant atom 57Fe. Obtained spectral parameters, viz., the average magnetic hyperfine field, the average isomer shift, and the probability of the atomic configuration with no impurity atoms in the two‐shell vicinity of the iron atoms, reach saturation values from which the solubility limit of chromium in iron can be determined. On the other hand, the solubility limit of iron in Cr‐rich phase can be estimated from the value of the isomer shift of the single‐line in the spectrum annealed for the longest time. [ABSTRACT FROM AUTHOR]

Oxide dispersion strengthened steels are key alloys used in nuclear installations. Steels with chromium content of up to 10 wt % are suitable due to their advantageous properties and these alloys are used for the construction of technological devices in the primary circuit of nuclear power plants. From other studies, it can be concluded that chromium has anti-corrosive properties due to the formation of a passivation layer, which results in reduced activation of the material by thermal neutrons. Macroscopic properties are determined by their microstructure, and therefore, the description of the microstructure is important. Transmission Mössbauer spectroscopy and atom probe tomography were used to characterise the material. This provides information about the physical and/or chemical environment of the resonant atoms can be obtained. Obtained spectral parameters reach saturation values from which the solubility limit of chromium in iron can be determined. In Cr-rich phase, the solubility limit can be estimated from the value of spectral parameters of the single-line in the spectrum annealed for the longest time. The suggested procedures are subsequently applied to the case studies of stainless steels suitable for the construction of various components of the III+/IVth generation of nuclear reactors (including fast and fusion reactors).

Effect of electron irradiation on electronic structure of Ni41Co6Mn43Sn10 alloys were investigated by X-ray absorption fine structure, X-ray magnetic circular dichroism spectrometry and Mössbauer spectrometry. The local coordination environment of magnetic element significant changes after electron irradiation, the change in the peak intensity of the Co L3 edge is opposite to the Ni/Mn element, indicating that there is an electronic exchange between them. The crystal field symmetry is broken, the hyperfine field Hin of the Ni41Co6Mn43Sn10 alloy increases from 8.80 to 9.06 T. Meanwhile, the spin magnetic moment of the Mn atom is significantly increased after electron irradiation. [ABSTRACT FROM AUTHOR]

In this work an attempt is made to study the impact of the quenching rate upon structure, hyperfine interactions, magnetic and mechanical properties of Fe78Si9B13 metallic glasses. Other involved parameters in melt spinning method were kept invariant. Analytical techniques comprising X-ray diffraction, transmission Mössbauer spectrometry, vibration sample magnetometer, Vickers microhardness and differential scanning calorimetry were employed. Minor effect of quenching rate upon the macroscopic magnetic properties was detected. It was shown that notable changes in the local atomic arrangement, structure, and mechanical properties were unveiled, dominantly by represent the crystallization at the lowest quenching rate. [ABSTRACT FROM AUTHOR]

Fe78B15Sn7 and (Fe3Co1)78B15Sn7 amorphous metallic alloys were prepared using the method of planar flow casting. The amorphous nature of ribbons containing 7 at. % Sn was verified by X-ray diffraction. The resulting chemical composition was checked by flame atomic absorption spectroscopy and by mass spectrometry with inductively coupled plasma. The microstructure of the as-quenched metallic glasses was investigated by 57-Fe and 119-Sn Mössbauer spectrometry. The experiments were performed with transmission geometry at 300 K, 100 K, and 4.2 K, and in an external magnetic field of 6 T. The replacement of a quarter of the Fe by Co did not cause significant modifications of the hyperfine interactions in the 57-Fe nuclei. The observed minor variations in the local magnetic microstructure were attributed to alterations in the topological short-range order. However, the in-field 57-Fe Mössbauer spectra indicated a misalignment of the partial magnetic moments. On the other hand, the presence of Co considerably affected the local magnetic microstructure of the 119-Sn nuclei. This was probably due to the higher magnetic moment of Co, which induces transfer fields and polarization effects on the diamagnetic Sn atoms.

This investigation reports the synthesis and characterization of (1-x)Ni0.5Zn0.5Fe2O4/(x)Zn0.95Co0.05O nanocomposites, with 0.0 ≤ × ≤ 0.5. Fourier transform infrared (FTIR) and Raman spectroscopies confirmed the purity of the samples and the presence of bands corresponding to octahedral and tetrahedral iron occupancies for Ni0.5Zn0.5Fe2O4 nanoparticles. A shift in peak positions of these bands was detected upon the addition of Zn0.95Co0.05O nanoparticles. The magnetic properties of the nanocomposites were examined using Mössbauer spectrometry at both room temperature and 77 K. Room temperature analysis showed the existence of both ferromagnetic and superparamagnetic behaviors, while at 77 K, all nanocomposites showed ferromagnetic behavior. The adsorption performance of the nanocomposite on the removal of malachite green (MG) dye solution was investigated by varying the contact time, adsorbent concentration, and reaction temperature. The adsorption reaction followed the second-order kinetics and the sample with x = 0.3 showed the highest adsorption rate. The adsorption rate showed an increase with the increase in the reaction temperature. The adsorption isotherm was determined by applying different adsorption isotherms (Langmuir, Freundlich, and Temkin isotherms), and the results are well-fitted with the Langmuir theoretical model. [ABSTRACT FROM AUTHOR]

Iron-based compounds with a ThMn12-type structure have the potential to bridge the gap between ferrites and high performance Nd2Fe14B magnets. From the point of view of possible applications, the main advantage is their composition, with about 10 wt.% less rare earth elements in comparison with the 2:14:1 phase. On the other hand, the main issue delaying the development of Fe-rich alloys with a ThMn12-type structure is their structural stability. Therefore, various synthesis methods and stabilizing elements have been proposed to stabilize the structure. In this work, the influence of increasing Nd substitution on the phase constitution of Zr0.4−xNdxCe0.6Fe10Si2 (0 ≤ x ≤ 0.3) alloys was analyzed. X-ray diffraction and 57Fe Mössbauer spectrometry were used as the main methods to derive the stability range and destabilization routes of the 1:12 structure. For the arc-melted samples, an increase in the lattice parameters of the ThMn12-type structure was observed with the simultaneous growth of bcc-(Fe,Si) content with increasing Nd substitution. After isothermal annealing, the ThMn12-type structure (and the coexisting bcc-(Fe,Si)) were stable over the whole composition range. While the formation of a 1:12 phase was totally suppressed in the as-cast state for x = 0.3, further heat treatment resulted in the growth of about 45% of the ThMn12-type phase. The results confirmed that the stability range of ThMn12-type structure in the Nd-containing alloys was well improved by other substitutions and the heat treatment, which in turn, is also needed to homogenize the ThMn12-type phase. After further characterization of the magnetic properties and optimization of microstructure, such hard/soft magnetic composites can show their potential by exploiting the exchange spring mechanism. [ABSTRACT FROM AUTHOR]

• Fine-grained street dust is most enriched in heavy metals and magnetic particles. • Iron is the most abundant in the residual fraction followed by reducible fraction. • Residual and reducible fractions bind a considerable percentage of heavy metals. • Hematite, metallic iron, and iron carbides are distinctive street dust components. Street dust is one of the most important carriers of heavy metals (HMs) originating from natural and anthropogenic sources. The main purpose of the work was to identify which of Fe-bearing phases bind HMs in street dust. Magnetic parameters of the Fe-bearing components, mainly magnetically strong iron oxides, are used to assess the level of HM pollution. Chemical sequential extraction combined with magnetic methods (magnetic susceptibility, magnetization, remanent magnetization) allowed determining the metal-bearing fractions and identifying the iron forms that are mostly associated with traffic-related HMs. The use of Mössbauer spectrometry (MS) supplemented by magnetic methods (thermomagnetic curves and psarameters of hysteresis loops) enabled precise identification and characterization of iron-containing minerals. The classification of HMs into five chemical fractions differing in mobility and bioaccessibility revealed that iron is most abundant (over 95%) in the residual fraction followed by the reducible fraction. HMs were present in reducible fraction in the following order: Pb>Zn>Mn>Cr>Ni>Fe>Cu, while they bound to the residual fraction in the following order: Fe>Ni>Cr>Mn>Pb>Cu>Zn. The signature of the anthropogenic origin of street dust is the presence of strongly nonstoichiometric and defected grains of magnetite and their porous surface. Magnetite also occurs as an admixture with maghemite, and with a significant proportion of hematite. A distinctive feature of street dust is the presence of metallic iron and iron carbides. Magnetic methods are efficient in the screening test to determine the level of HM pollution, while MS helps to identify the iron-bearing minerals through the detection of iron. [Display omitted] [ABSTRACT FROM AUTHOR]

The objective of this work is to evaluate the applicability of exchange coupling between nanoparticles of Nd2Fe14B (hard magnetic material) and Fe90Al10 (soft magnetic material), as permanent magnets produced by surfactant-assisted mechanical alloying. The obtained powders were then mixed with 85% of the Nd2Fe14B system and 15% of the Fe90Al10 system and subsequently sintered at 300 °C, 400 °C and 500 °C for one hour. The results obtained by Mössbauer spectrometry (MS) show a ferromagnetic behavior with six magnetic sites represented by sextets (16k1, 16k2, 8j1, 8j2, 4c and 4e), characteristic of the Nd2Fe14B system. X-ray diffraction (XRD) results show a tetragonal and BCC structure for the Nd2Fe14B and FeAl systems, respectively. The results obtained by vibrating sample magnetometry (VSM), for mixtures of the Nd2Fe14B and Fe90Al10 sy stems sintered at 300 °C, 400 °C and 500 °C, allow for the conclusion that the coercive field (Hc) decreases drastically with temperature and the percentage of soft phase at values of Hc = 132 Oe compared to the coercive field values reported for Nd2Fe14B Hc = 6883 Oe, respectively. Images obtained by transmission electron microscopy (TEM), for the Fe90Al10 system, show a tendency for the nanoparticles to agglomerate. [ABSTRACT FROM AUTHOR]

Fe-O-N films were successfully deposited by magnetron sputtering of an iron target in Ar-N2-O2 reactive mixtures at high nitrogen partial pressure 1.11 Pa (Q(N2) = 8 sccm) using a constant flow rate of argon and an oxygen flow rate Q(O2) varying from 0 to 1.6 sccm. The chemical composition and the structural and microstructural nature of these films were characterized using Rutherford Backscattering Spectrometry, X-ray diffraction, and Conversion Electron Mössbauer Spectrometry, respectively. The results showed that the films deposited without oxygen are composed of a single phase of γ ″ -FeN, whereas the other films do not consist of pure oxides but oxidelike oxynitrides. With higher oxygen content, the films are well-crystallized in the α-Fe2O3 structure. At intermediate oxygen flow rate, the films are rather poorly crystallized and can be described as a mixture of oxide γ -Fe2O3/Fe3O4. In addition, the electrical behavior of the films evolved from a metallic one to a semiconductor one, which is in total agreement with other investigations. Comparatively to a previous study carried out at low nitrogen partial pressure (0.25 Pa), this behavior of films prepared at higher nitrogen partial pressure (1.11 Pa) could be caused by a catalytic effect of nitrogen on the crystallization of the hematite structure. [ABSTRACT FROM AUTHOR]

Herein, several ways to evaluate Mössbauer spectra of model binary Fe100−xCrx alloys with chromium content varying in the range from 1 to 50 at% (x = 0.94, 2.2, 4.9, 10.4, 15.4, 22.1, and 52.9) are discussed. For low chromium concentrations (up to 15 at%), the method of binomial distribution of individual sextets is suitable. Depending upon the Cr content, the number of sextets used can be, however, as high as 20. The specific number of sextets is determined according to probabilities of individual atomic sites calculated from binomial distribution. Mössbauer spectra of samples with Cr concentrations higher than 20 at% are evaluated by distributions of hyperfine magnetic fields. The composition of model alloys is verified using X‐ray fluorescence. Their surface is analyzed by two different surface‐sensitive methods: scanning electron microscopy and atomic force microscopy. The main technique used to analyze the materials' subsurface layers is conversion electron Mössbauer spectroscopy. The applied fitting models and results are useful in studies of the microstructure of real types of construction and stainless steels. [ABSTRACT FROM AUTHOR]

Herein, we reported a successful synthesis of spinel ferrites MFe2O4 (M = Ni, Co, and Mg) nanopowders through heat treatment of carbonate-intercalated layered double hydroxide (MFe–CO3–LDH) precursors at 600 and 1000 °C for 2 h. The physicochemical properties of as-synthesized LDHs and resulting calcined products were investigated using X-ray diffraction, thermogravimetric/differential thermal analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, magnetic measurements and Mössbauer spectrometry. The results reveal the formation of a single-phase spinel crystal structure of space group Fd-3m. The effect of calcination temperature on the structural and magnetic properties of ferrite nanoparticles was discussed in detail. The Ni2+, Co2+, and Mg2+ substitution on the structure resulted in significant changes in the crystal composition, surface morphology, particle size, and magnetic properties of spinel ferrites. Furthermore, the effects of calcination on the structural and magnetic phase transformation of iron-containing LDH precursors have been also studied by Mössbauer spectrometry at room temperature. The M(H) curves at 5 K revealed a soft magnetic behaviour for both Ni and Mg calcined products, while Co spinel ferrite shows wasp-waist magnetic nature which is discussed in present study. By comparing to reported works in literature, the calcination effect on the present LDH samples has relatively improved the saturation magnetization property. [ABSTRACT FROM AUTHOR]

• A macroscopic and a local approach are used to study the universality class. • The value of TC increases by the substitution of a Pr atom by a Sm atom. • The order of the phase transition is identified based on the Banerjee criterion. • The determined exponents are close to 3D-Ising [ d = 3 : n = 1 ] spins coupled with an interaction at the boundary between a long-range and a short-range type interaction. • The universality class of the compounds studied in this paper may be correlated with the anisotropy of the near neighbors. [Display omitted] Achieving a comprehensive understanding of the properties and behaviors of magnetic phase transitions and critical behavior is a key objective of this study. A macroscopic approach utilizing magnetization measurement and a local approach utilizing 57Fe Mössbauer spectrometry were employed. The findings indicate that the critical exponents of Pr 2 Fe 17 and (Pr,Sm) 2 Fe 17 closely approximate those of the 3D-Ising model, as confirmed by the scaling analysis of our critical exponents. Moreover, we observed that isotherms collapse into two distinct and independent universal branches above and below the Curie temperature when utilizing the critical exponents we obtained. Our results indicate that the exponents determined using both conventional methods and Mössbauer spectrometry closely match those of the 3D-Ising model for spins coupled in three dimensions (lattice dimensionality d = 3 , spin dimensionality n = 1) with attractive interactions between spins (J (r)) at the boundary of short-range and long-range decay as J (r) ∝ r − (3 + σ) . [ABSTRACT FROM AUTHOR]

• High-coercivity nanostructured Nd-Fe-B alloy powder synthesized. • The influence of the stoichiometric composition on the magnetic properties is investigated. • The influence of iron content on coercivity is investigated. • Higher Nd and B contents enhance the formation of the high-coercivity Nd 2 Fe 14 B phase. • X-ray diffraction analysis reveals the tetragonal crystal structure of the nanostructured Nd-Fe-B alloy. For the first time, a nanostructured alloy powder with high coercive force was obtained by a chemical method without the addition of Dy, which can compete with physical methods of production. The work carried out a study of the influence of stoichiometric composition on the magnetic properties of nanostructured Nd-Fe-B alloys. Alloys with different contents of Nd, Fe, and B were synthesized: Nd 12 Fe 84 B 6 , Nd 14 Fe 80 B 6 , Nd 16 Fe 76 B 8 , and Nd 16 Fe 72 B 8. With a decrease in the iron content in the first two compositions, a decrease in the iron content in the soft magnetic phase α-Fe was observed, which led to an increase in the coercive force H c and a decrease in the values of M s and M r. Experiments have shown that an increase in the content of Nd and B promotes the formation of the hard magnetic phase Nd 2 Fe 14 B and an increase in the coercive force. For example, the nanostructured Nd 16 Fe 76 B 8 alloy demonstrated a maximum coercive force of H c = 8439 Oe, while compensating for the values of M s (109 emu*g−1) and M r (78 emu*g−1). A comprehensive study of the nanostructured Nd 16 Fe 76 B 8 alloy was carried out, including structural analysis. XRD using FullProff and Vesta software revealed the tetragonal crystal structure of the Nd 2 Fe 14 B phase, providing details of the atomic arrangement. The unit cell contains four layers with Nd and Fe atoms, and boron atoms are embedded in the center of the octahedron of Nd and Fe atoms, playing an important role in the magnetic exchange interaction. The results of Mössbauer spectroscopy confirmed the presence of the Nd 2 Fe 14 B phase and revealed details of the state of Fe atoms in the structure of six sextets. [ABSTRACT FROM AUTHOR]

Iron-based compounds with a ThMn12-type structure have the potential to bridge the gap between ferrites and high performance Nd2Fe14B magnets. From the point of view of possible applications, the main advantage is their composition, with about 10 wt.% less rare earth elements in comparison with the 2:14:1 phase. On the other hand, the main issue delaying the development of Fe-rich alloys with a ThMn12-type structure is their structural stability. Therefore, various synthesis methods and stabilizing elements have been proposed to stabilize the structure. In this work, the influence of increasing Nd substitution on the phase constitution of Zr0.4−xNdxCe0.6Fe10Si2 (0 ≤ x ≤ 0.3) alloys was analyzed. X-ray diffraction and 57Fe Mössbauer spectrometry were used as the main methods to derive the stability range and destabilization routes of the 1:12 structure. For the arc-melted samples, an increase in the lattice parameters of the ThMn12-type structure was observed with the simultaneous growth of bcc-(Fe,Si) content with increasing Nd substitution. After isothermal annealing, the ThMn12-type structure (and the coexisting bcc-(Fe,Si)) were stable over the whole composition range. While the formation of a 1:12 phase was totally suppressed in the as-cast state for x = 0.3, further heat treatment resulted in the growth of about 45% of the ThMn12-type phase. The results confirmed that the stability range of ThMn12-type structure in the Nd-containing alloys was well improved by other substitutions and the heat treatment, which in turn, is also needed to homogenize the ThMn12-type phase. After further characterization of the magnetic properties and optimization of microstructure, such hard/soft magnetic composites can show their potential by exploiting the exchange spring mechanism.

In the recent decade, magnetic compounds have attracted a great deal of interest due to their magnetic behaviour allowing them to be a good candidate for catalytic and biomedical applications. However, the problem of these materials is their aggregation during the synthesis process, and then problems related to particle size. To overcome these problems, an efficient assembly of magnetic nanoparticles with layered double hydroxides compound systems (Fe-NPs@LDH and M/Fe-NPs@LDH; M = Mn, Zn) were prepared by simple co-precipitation process. Analytical tools including TG-dTG, XRD, FTIR, SEM/EDX and BET were used to investigate the thermal, morphological, structural and textural properties of the studied materials. The magnetic properties of the composite were investigated by mean 57Fe Mossbauer spectrometry. [ABSTRACT FROM AUTHOR]

The objective of this work is to evaluate the applicability of exchange coupling between nanoparticles of Nd2Fe14B (hard magnetic material) and Fe90Al10 (soft magnetic material), as permanent magnets produced by surfactant-assisted mechanical alloying. The obtained powders were then mixed with 85% of the Nd2Fe14B system and 15% of the Fe90Al10 system and subsequently sintered at 300 °C, 400 °C and 500 °C for one hour. The results obtained by Mössbauer spectrometry (MS) show a ferromagnetic behavior with six magnetic sites represented by sextets (16k1, 16k2, 8j1, 8j2, 4c and 4e), characteristic of the Nd2Fe14B system. X-ray diffraction (XRD) results show a tetragonal and BCC structure for the Nd2Fe14B and FeAl systems, respectively. The results obtained by vibrating sample magnetometry (VSM), for mixtures of the Nd2Fe14B and Fe90Al10 sy stems sintered at 300 °C, 400 °C and 500 °C, allow for the conclusion that the coercive field (Hc) decreases drastically with temperature and the percentage of soft phase at values of Hc = 132 Oe compared to the coercive field values reported for Nd2Fe14B Hc = 6883 Oe, respectively. Images obtained by transmission electron microscopy (TEM), for the Fe90Al10 system, show a tendency for the nanoparticles to agglomerate.

The microstructure of mechanically milled Nd2Fe14B, SmCo5/Fe and SmCo3Cu2/α-Fe alloys has been investigated by Mössbauer spectrometry and atom probe tomography. The structural changes that occur upon milling and subsequent annealing were characterised at a nanometer scale. Milling promotes intermixing of the elements and the formation of nanograins. In Nd-Fe-B powders, the Nd2Fe14B phase is transformed into α-Fe and an amorphous Nd-Fe-B phase. In SmCo5/Fe powders, Fe/Co intermixing occurs, leading to the formation of Sm(Co,Fe)5 and α-Fe(Co) phases. In SmCo3Cu2/Fe powders, although Sm is partly oxidised, Fe/Co intermixing occurs as well, leading to the formation of α-Fe(Co) nanograins surrounded by Sm(Co,Cu,Fe)5 intergranular regions. The combined Mössbauer and atom probe tomography investigation of rare earth / transition metal powders thus allows revealing the effect of mechanical milling and subsequent annealing on the nanostructure of the powders. These results are helpful for the understanding of the magnetic properties of the powders. [ABSTRACT FROM AUTHOR]

In the present work, the structural, magnetic, and theoretical analysis of the Fe–Si alloy prepared by melting and heat-treated was performed. The ordered FeSi simple cubic (sc) phase was obtained by melting and heat treatment processes as determined by X-ray diffraction. The presence of the superstructure peak in the (312) crystalline direction confirms the high structural order reached. Using Mössbauer spectrometry (MS), a paramagnetic behavior with quadrupole splitting of SQ = 0.53 ± 0.02 mm/s was obtained. Although MS indicates paramagnetic behavior, vibrating sample magnetometry (VSM) showed ferromagnetic behavior with a coercive field of 25 Oe, associated with a small amount of Fe3Si segregations detected by scanning electron microscopy/energy dispersive spectrometry (SEM/EDS). Using density functional theory (DFT), the crystalline structures for the simple cubic (sc) Fe50Si50, face-centered cubic (fcc) Fe3Si, and body-centered cubic (bcc) Fe3Si crystalline structures were simulated. Electron total density values were calculated to perform energetic comparisons with magnetic behavior. The electronic structures and magnetic properties of the Fe–Si alloys in different stoichiometric configurations were calculated by CASTEP, which employed first principles DFT. The density of states (DOS) and band structures were calculated together with magnetic properties. The results showed that the high value of the polarization spin for the fcc and bcc structures is due to the contribution of the high amount of Fe atoms above the Si atoms, which is reflected in an increase in the magnetic moment and that their presence could explain the ferromagnetic behavior observed by VSM. [ABSTRACT FROM AUTHOR]

This review discusses the properties of candidate compounds for semi-hard and hard magnetic applications. Their general formula is R1−sT5+2s with R = rare earth, T = transition metal and 0≤s≤0.5 and among them, the focus will be on the ThMn12- and Th2Zn17-type structures. Not only will the influence of the structure on the magnetic properties be shown, but also the influence of various R and T elements on the intrinsic magnetic properties will be discussed (R = Y, Pr, Nd, Sm, Gd, … and T = Fe, Co, Si, Al, Ga, Mo, Zr, Cr, Ti, V, …). The influence of the microstructure on the extrinsic magnetic properties of these R–T based intermetallic nanomaterials, prepared by high energy ball milling followed by short annealing, will be also be shown. In addition, the electronic structure studied by DFT will be presented and compared to the results of experimental magnetic measurements as well as the hyperfine parameter determined by Mössbauer spectrometry.

The aim of this research work was to study the structural and magnetic properties of iron oxide nanoparticles. The as-prepared sample was synthesized by a co-precipitation route and annealed at different temperatures. The annealed samples were investigated using different techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), vibrating sample magnetometry (VSM), and Mössbauer spectrometry (MS). The XRD results indicate the formation of three phases which have been identified as magnetite (Fe3O4), maghemite (γ-Fe2O3), and hematite (a-Fe2O3). The crystallite size was very similar for both magnetite and maghemite, and it was higher for hematite. The TEM observations showed that the particle shapes were affected by the annealing temperature (Tan). In addition, the SEM analysis revealed a wide distribution of the particle size. The magnetic measurements enabled the determination of a blocking temperature for both Fe3O4 and γ-Fe2O3 as 210 and 240 K, respectively. The Morin transition temperature was determined in the case of α-Fe2O3 from the magnetization and the MS measurements. The synthesized iron oxide nanoparticles can be good candidates for hyperthermia applications. [ABSTRACT FROM AUTHOR]

Magnetic nanoparticles MnFe2-xMoxO4 (x = 0.00, 0.04, 0.08 and 0.10) have been prepared by wet coprecipitation method at calcination temperature 673 K. X-ray powder diffraction (XRD) was used to study the structural properties of the prepared samples, whereas the vibrating sample magnetometer (VSM) and Mössbauer spectrometry measurements (at T = 300 K and T = 77 K) were used to investigate the magnetic properties. The single-phase cubic spinel structure of the ferrites samples was confirmed by the XRD patterns, and a nonlinear variation in the crystalline size was revealed. VSM hysteresis loops confirmed the ferromagnetic behavior in all the samples with an increase in saturation magnetization with the molybdenum doping. Mössbauer spectra at 300 K showed a mixture of the magnetic sextet and central quadrupole doublet with enhancement in the magnetic sextet in the Mo-doped samples. Moreover, Mössbauer spectra at 77 K revealed the disappearance of the quadrupole doublet in all samples, indicating the enhancement of magnetic properties of manganese ferrites nanoparticles due to Mo-doping. [ABSTRACT FROM AUTHOR]

Polycrystalline samples of the series of triple perovskites Sr3−xPbxFe2TeO9 (0 ≤ x ≤ 2.25) (SPFTO) were synthesized using solid state reaction. These materials have been studied by a combination of X-ray powder diffraction (XRPD), Mössbauer spectrometry, Raman and UV–Vis spectroscopies. The crystal structures were resolved by the Rietveld refinement method, and revealed that this Sr3−xPbxFe2TeO9 (0 ≤ x ≤ 2.25) system shows one space group change from tetragonal I4/m (0 ≤ x ≤ 1) to another tetragonal form I4/mmm (1.25 ≤ x ≤ 1.88) and a second transition to hexagonal R 3 ¯ m (2.08 ≤ x ≤ 2.25). An anti-site disordering of Fe and Te on the B sites has been detected indicating the presence of a partial amount of Te at Fe positions and vice versa. The valence state of iron in the Fe site was determined to be Fe(III) by Mössbauer spectrometry, which also revealed two sites in a concordance with the XRPD measurements. 57Fe Mössbauer spectra measurements show paramagnetic and magnetic ordering behaviors. The observed Raman spectra as a function of composition show obvious changes on the positions (wavenumbers), the FWHM and the intensities of the modes confirming the phase transformations observed by the XRPD results. These structural transitions led to a distinct change in the optical band gap energy, varying from 2.14 to 1.85 eV. [ABSTRACT FROM AUTHOR]

Magnetic ordering in Fe51Co12Si16B8Mo5P8 metallic glass is followed by 57Fe transmission Mössbauer spectrometry performed at temperatures ranging from 4.2 K up to 415 K. Low temperature experiments were accomplished also in external magnetic field of 6 T oriented parallel to the ribbon plane. Evolution of Mössbauer spectra with sample temperature shows gradual vanishing of hyperfine magnetic fields. High temperature Mössbauer spectra exhibit clear transition from ferromagnetic to paramagnetic state. In this way, the Curie temperature can be determined. We have concentrated on samples annealed at 573 K and 673 K, i.e., well below the onset of crystallization. Measurements at 4.2 K revealed rearrangement of spins that is taking place both after the annealing, as well as in external magnetic field. From high temperature experiments, the Curie temperature of 400 K was determined for the sample annealed at 673 K. [ABSTRACT FROM AUTHOR]

Fe2+ ions in Fe7(P2O7)4 were substituted by Zn2+and the magnetic properties and Mössbauer spectra of the new material were studied. The obtained sample of Zn5Fe2(P2O7)4 is isostructural with the parent Fe7(P2O7)4, which is orthorhombic with a C2221 space group. Magnetometry shows that the Néel temperature is TN = 15.4(1) K, which is in accordance with Mössbauer measurements performed at RT and 4.2 K. [ABSTRACT FROM AUTHOR]

Examination of surface microstructure of stainless steels is presented. Transmission Mössbauer spectrometry and Conversion Electron Mössbauer Spectrometry which provide information from the bulk and surface regions, respectively, were used. We concentrate on structural modifications that were caused by surface treatments including grinding, polishing, and electrolytic etching. Scanning Electron Microscopy with Energy Dispersive Spectrometry was adopted for visualization of surface differences. Formation of magnetic phases was revealed in the surface regions of X6CrNiTi1810 steel while no substantial effect of surface treatment was found in the ATABOR steel. Bulk regions in both steels are not affected by surface treatment. [ABSTRACT FROM AUTHOR]

Sorption of oxyanions onto ferric oxyhydroxides' surfaces is naturally occurring process with advantageous implications in remediation of contaminated waters or management of landfills. Therefore, this paper provides information on selenite sorption onto goethite, which is one of the most common oxyhydroxides in the environment. Our results showed that selenite sorption was well described by the pseudo-second-order kinetic model, as well as by Langmuir isotherm. This suggests chemisorption as a rate-controlling step and formation of selenite monolayer on goethite surface with relatively high 83.8 µmol g−1 maximum sorption capacity at pH 3, which was determined for initial selenite concentration in the range of 45–550 µmol L−1 in 0.5 g L−1 (m/v) goethite suspension. The Mössbauer analysis revealed only marginal structural changes in goethite during sorption. Our results also showed that pH significantly affects the overall sorption rate constant with the highest values at the acidic region. Study on competitive sorption behaviour highlighted significant influence of phosphate on selenite sorption. There was no competition for sorption positions with excessive concentrations of sulphate and chloride ions. However, equimolar concentrations of sulphate and chloride led to changes in selenite sorption efficiency. Our results showed that selenite sorption onto goethite is a viable method for selenite removal and, thus, goethite can be successfully applied as a component in commercial composite sorbents or in geochemical barriers. [ABSTRACT FROM AUTHOR]

The Z-element related structural and physical properties of the Co 2 FeZ Heusler alloys prepared by arc melting were subjected to detail bulk and surface studies. The several experimental methods as scanning and transmission electron microscopy, X-ray diffraction, positron annihilation, Mössbauer spectroscopy, completed by magnetic and hardness measurements were applied. The main attention was devoted to differences in all possible properties as morphology, defects, micro- and macro-magnetic behaviour and microhardness depending upon a choice of Si, Al, or Si + Al as the Z element. The best structural homogeneity, smallest grain size, and no grain boundary segregation were observed at Co 2 FeSi 0.5 Al 0.5 , while about ten-times larger grains were obtained at Co 2 FeSi, the grain boundaries of which were covered by a thin interfacial phase, and at Co 2 FeAl with formation of dendritic structure. Nearly all physical parameters obtained for the Co 2 FeSi 0.5 Al 0.5 alloy were found to be influenced by either Si or Al. [ABSTRACT FROM AUTHOR]

Due to their excellent magnetic properties, amorphous metallic alloys (AMAs) are considered for the construction of magnetic cores of radio-frequency cavities in accelerators. Here, they might be exposed to ion bombardment. The influence of irradiation by both light and heavy ions featuring low and high energies, respectively, is followed by the techniques of 57Fe Mössbauer spectrometry. Modifications of surface layers in selected Fe-containing AMAs after ion irradiation are unveiled by detection of conversion electrons and photons of characteristic radiation whereas those in their bulk are derived from standard transmission spectra. Rearrangement of microstructure which favors the formation of magnetically active regions, is observed in surface regions bombarded by light ions. Heavy ions caused pronounced effects in the orientation of net magnetization of the irradiated samples. No measurable impact upon short-range order arrangement was observed. Part I of this paper is devoted to radiation effects in Fe-based AMAs induced by neutron irradiation.

Iron-based amorphous metallic alloys (AMAs) of several compositions were exposed to neutron irradiation with fluences of up to 1019 n/cm2. These materials exhibit excellent magnetic properties which predetermine them for use in electronic devices operated also in radiation-exposed environments. Response of the studied AMAs to neutron irradiation is followed by Mössbauer spectrometry which probes the local microstructure. Neutron irradiation leads to rearrangement of constituent atoms, their clustering, and formation of stress centers. The observed modifications of topological short-range order result in changes of spectral parameters including average hyperfine magnetic field, ⟨B⟩, standard deviation of the distribution of hyperfine fields, and position of the net magnetic moment. After irradiation, especially differences in ⟨B⟩-values develop in two opposite directions. This apparent controversy can be explained by formation of specific atomic pairs with different exchange interactions, which depend on the composition of the samples. Part II of this paper will be devoted to radiation effects caused in Fe-based AMAs by ion irradiation.

In this paper, the results of the complex examination of the 42CrMo4 steel samples are presented. The samples were taken from the metallurgical forging prepared for the production of the wind turbine main shaft. The samples underwent Mössbauer spectroscopic analysis, as well as the measurement of its mechanical characteristics such as hardness and strength are analysed. Conversion electron Mössbauer spectrometry confirmed phase purity and isotropy of the investigated 42CrMo4 steel. The method provided accurate results, proving Mössbauer spectrometry to be an effective tool for the wind turbine main shaft analysis.

Several samples of dusts from steel and coke plants (collected mostly with electro filters) were subjected to the investigation of content of mineral phases in their particles. Additionally, sample of bog iron ore and metallurgical slurry was studied. Next, the magnetic susceptibility of all the samples was determined, and investigations of iron-containing phases were performed using transmission Mössbauer spectrometry. The values of mass-specific magnetic susceptibility χ varied in a wide range: from 59 to above 7000 × 10−8 m-3·kg−1. The low values are determined for bog iron ore, metallurgical slurry, and coke dusts. The extremely high χ was obtained for metallurgical dusts. The Mössbauer spectra and X-ray diffraction patterns point to the presence of the following phases containing iron: hematite and oxidized magnetite (in coke and metallurgical dusts as well as metallurgical slurry), traces of magnetite fine grains fraction (in metallurgical dusts), amorphous glassy silicates with paramagnetic Fe3+ and Fe2+ ions, traces of pyrrhotite (in coke dusts), α-Fe and nonstoichiometric wüstite (in metallurgical slurry), as well as ferrihydrite nanoparticles (in bog iron ore). For individual samples of metallurgical dusts, the relative contributions of Fe2+/3+ ions in octahedral B sites and Fe2+ ions in tetrahedral A sites in magnetite spinel structure differs considerably.

Variability in iron species in marine deposits are excellent geochemical archives for exploring variations in redox conditions during early diagenesis and seepage dynamics over time. Two sediment cores (DS07 and DS08) were collected in the Jiulong Methane Reef, a typical cold seep site that is located in the South China Sea (SCS), and analyzed for iron species using Mössbauer spectrometry and magnetic procedures. Excluding the surface layer (0-10 cm) in DS07, Fe2+/Fe3+ ratios indicated that core sediments were under anoxic conditions. The Fe2+/Fe3+ and frequency-dependent susceptibility (χ fd) at this site were higher while the total organic matter content (TOC) and magnetic susceptibility (χ) were significantly lower at approximately 170 cm depth. Combined with chromium reducible sulfur (CRS), Fe/Al and sulfur to organic content (S/C) ratios suggested that there was a sulfate-methane transition zone (SMTZ) at approximately 170 cm. Moreover, thermomagnetic analyses indicated that magnetite was the dominant ferrimagnetic mineral at 21–23 cm, 165–185 cm, 213–233 cm and 285–295 cm depths, however, magnetite content was relatively lower between the 165 and 185 cm depth, which suggested that magnetite had been largely transformed to paramagnetic iron minerals during the anaerobic oxidation of methane (AOM) process. The DS08 sediment core was also mostly anoxic , however, no obvious methane seepage activity was observed because the maximum values of Fe2+/Fe3+, Fe/Al, CRS, S/C and the minimum values of TOC and χ did not simultaneously occur at the same depth. The study revealed that the speciation of Fe in sediment cores varied under different redox conditions which was of interest when utilizing iron speciation and magnetic minerals as indicators of historical environmental conditions and seepage activities. Image 1 • Fe species were characterized by Mössbauer spectra and magnetic analysis. • DS07 and DS08 were almost in reducing condition except the surface sediment. • Transient methane seepage occurred around 170 cm in DS07. • There was no obvious SMTZ in DS08. • Fe species could be used to trace redox conditions, especially for CH 4 seepage. [ABSTRACT FROM AUTHOR]

The structural properties and magnetic behavior of the Fe50Si50 system were determined using X-ray diffraction (XRD), Mössbauer spectrometry (MS), vibration sample magnetometry (VSM), and scanning electron microscopy (SEM). Samples of Fe50Si50 were melted using an arc furnace, then powder was obtained through a diamond file, and this was passed through different sieves. Finally, nanoparticles of this system were produced by means of surfactant-assisted mechanical alloying. XRD confirmed the presence of the FeSi (CS) and Fe5Si3 structural phases. By transmission MS, it was observed that at room temperature the spectrum is formed by three general components, a doublet associated with the FeSi (CS) phase and two sextets associated with the Fe5Si3 phase; this gives the idea of the distribution of the sizes of particles present in the sample. By VSM, the soft magnetic behavior of the system was ratified and it was determined that the biggest saturation magnetization corresponds to the smallest particles. [ABSTRACT FROM AUTHOR]

Structural studies of Zn2+Fe 2 3 + (P2O7)2 and Cu0.5Zn0.5Fe2(P2O7)2 were made using powder X-ray diffraction and refined by Rietveld method. Both phosphates crystallize in an orthorhombic structure with Pnma space group. Magnetometry measurements showed that below TN = 5.6 (1), Zn2+Fe 2 3 + (P2O7)2 becomes antiferromagnetic and the TN = 14 K is attributed to Cu0.5Zn0.5Fe2(P2O7)2. Mössbauer studies at room temperature and low temperature were performed in both samples. [ABSTRACT FROM AUTHOR]

Structural studies of Zn2+Fe 2 3 + (P2O7)2 and Cu0.5Zn0.5Fe2(P2O7)2 were made using powder X-ray diffraction and refined by Rietveld method. Both phosphates crystallize in an orthorhombic structure with Pnma space group. Magnetometry measurements showed that below TN = 5.6 (1), Zn2+Fe 2 3 + (P2O7)2 becomes antiferromagnetic and the TN = 14 K is attributed to Cu0.5Zn0.5Fe2(P2O7)2. Mössbauer studies at room temperature and low temperature were performed in both samples. [ABSTRACT FROM AUTHOR]

The structure, magnetic and magnetocaloric properties of arc-melted Gd2Fe17-xCux (x= 0, 0.5, 1 and 1.5) solid solution have been studied. The Rietveld refinement shows that these compounds crystallize in the rhombohedral Th2Zn17-type structure with the R3¯m space group, and the substitution of iron by copper leads to a decrease in the unit cell volume. The Curie temperature (TC) of the prepared samples depends on the copper content. The reduction of the ferromagnetic phase transition temperature from 475 K (for x=0) to 460 K (for x=1.5) is due to the substitution of the magnetic element (Fe) by non-magnetic atoms (Cu). The magnetocaloric effect was determined in the vicinity of the Curie temperature TC. By increasing the Cu content, an increase in the values of magnetic entropy (ΔSM) in a low applied field is observed. The preferred inequivalent crystallographic site of Cu atoms was determined by Mössbauer spectrometry analysis based on the isomer shift parameter correlation with the Wigner-Seitz cell volumes. [ABSTRACT FROM AUTHOR]