Hyperfine Interactions

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Article
A model has been devised to derive the intermetallic structure from the bcc- Fe unit cell. The fundamental finding is of special interest because the recent investigation clarifies that there is substantial evidence that atomic arrangements of transition metal-rich amorphous alloys are made of distorted bcc structure. The disordered bcc structure is thermodynamically in a metastable state, the heat treatment leads by crystallization of amorphous alloys to a stable state. In the past, a great deal has been made to describe the process of crystallization of amorphous alloys, but unfortunately, the disordered bcc-Fe regions of amorphous alloys have been neglected. Since the crystallization process takes place from the disordered bcc-regions of amorphous state, it is advisable to reexamine, discuss, and, where necessary to modify the product of the crystallization by the experimental achievements. It is therefore the objective of the present investigation to devise a model based on experimental facts. The atomic size of metalloid atoms determines the crystallization and crystal growth of amorphous alloy. Regardless of their structure, Mössbauer investigation on Fe-rich Metal-Metalloid alloys indicates that the metalloid atoms such as B, P, C, and Ge tend to act with iron by spending their electrons into the Fe 3d-band.
 
Article
Carbonatite is an igneous rock that is composed mainly of carbonate minerals and silicates. It is recently applied as fertilizer due to its high content of calcite and dolomite. This study presents a physical and chemical characterization of the Spanish River Carbonatite (SRC) and its application as fertilizer is tested. The chemical composition obtained by X-ray fluorescence and Energy Dispersive X-ray analyses indicates that Ca, Fe and Si are the main contained elements. Calcite and SiO2 are the principal mineralogical phases as detected by X-ray diffraction. Fourier transform infrared spectroscopy confirms the presence of calcite, silicates and also organic material and water. It also suggests the presence of vermiculite. Thermal analysis reveals only a one-step reaction that corresponds to the decomposition of calcite. Mössbauer spectroscopy performed at room temperature do not show magnetic order between the iron moments instead it shows Fe²⁺ and Fe³⁺ doublets in M1 and M2 octahedral sites belonging to vermiculite. At 50 K, we observe that the isomer shift increases their values due to the second order Doppler shift. SQUID magnetometry measurements reveal that most of the sample contains paramagnetic domains assigned to the silicates and calcite components. However, under low applied fields, a tiny signal for Verwey transition appears at 124 K (suggesting the presence of magnetite) although screened by the strong paramagnetic signal of the main components. The SRC has been tested as potential fertilizer on sweet cucumber (Solanum muricatum) which responded positively to the application to carbonatite as an amendment, expressing itself in high foliar biomass.
 
Article
The focus of this investigation is the interface regions in crystalline Fe-nanoparticles as well as amorphous nanograins with an average grain size of about 4 nm. The iron nanograins have been compacted under external pressure; the resulting region of the contact between the grains is called an interface. It was found that the interface was three-dimensional with an atomic order different from that present in the neighboring nanograins. The structure of the interfacial region between adjacent amorphous grains has been found to be similar to those in crystalline Fe-nanograins. In other words, the structure of the interface formed under external pressure is independent of the structure of the adjacent grains. The effect of the structure of the interfaces on the magnetic hyperfine interactions and the magnetic moments is studied. In addition, the atomic structures of the interfaces have been studied by means of synchrotron high energy X-ray diffraction. The results obtained are presented in the form of radial distribution functions suggesting the following atomic structure of interfaces: (1) a short-range order of clusters with distorted bcc cells and (2) a middle-range (mesoscopic) order different from that of the bcc cells.
 
Article
The Mössbauer effect (ME) spectroscopy is a powerful tool to obtain information about magnetic nanoparticles (NP). Here we correlate parameters that can be obtained from a ME spectrum (relative fractions of magnetite and maghemite and the volume dependent parameter λ=KV/kBT\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\lambda =KV/k_{B}T$$\end{document}) with other relevant quantities, such as DC saturation magnetization and X-ray diffraction NP mean diameter, DXRD\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_\text {XRD}$$\end{document}. The study was performed on the decanted pellets of six different batches of NP obtained using the same synthesis procedure. It was observed that λ1/3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\lambda ^{1/3}$$\end{document} presents a linear correlation with DXRD\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_\text {XRD}$$\end{document} from which the effective anisotropy K for the entire ensemble of the batches could be calculated. The fraction of magnetite retrieved from ME spectra was well correlated to the saturation magnetization. In addition, it was observed that the magnetic response of the supernatant obtained after washing and centrifuging the synthesis product, decreases with λ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\lambda$$\end{document}, according to the fact that larger NP decant more easily during centrifugation.
 
Schematic drawing of the chemical structure of DyPc2
Schematic drawing of the measurement system for ¹⁶¹Dy SR-based Mössbauer absorption spectroscopy
The intensity dependence on the Bragg angle of Si(18 12 6) in the HRM for ¹⁶¹Dy. Open circles are the experimental data and the lines are the fitting curve by the Gaussian function
The SR-based Mössbauer absorption spectra of DyF3 at Room temperature (up), Dy metal at 7 K (middle) and DyPc2 (down). The symbols with bars are experimental data, the bars are statistical errors, and the lines are the fitting curves by Lorentzian functions. The inclined baseline in the spectra were due to the arrangement of the scatterer and the detector
Article
We demonstrate a measurement system for synchrotron-radiation-based Mössbauer absorption spectra with ¹⁶¹Dy using the 25.7 keV nuclear first excited state. Mössbauer spectra of DyF3, Dy metal and DyPc2 (Pc = phthalocyaninato) were obtained and the parameters for the hyperfine structure of ¹⁶¹Dy nuclei in them were evaluated to demonstrate the feasibility of this method. Isomer shifts showed that Dy atoms in all of them are in trivalent state although those in Dy metal was in the region of trivalent metal region. The magnetic hyperfine field of Dy metal of 569 ± 1 T agreed with the literature of the Mössbauer experiments. That of DyPc2 of 489 ± 1 T was reasonable because the ground state of DyPc2 were in the state of Jz = ±13/2. Considering the highly penetrative nature of the 25.7 keV incident radiation, it will be straightforward to apply this method for the study of materials under various conditions such as high pressure, high magnetic fields, and reactive atmospheres.
 
Article
Within this work, we report the results of nuclear inelastic scattering experiments of the low-spin phase of the iron(II) mononuclear SCO complex Fe[HBpz 3 ] 2 and density functional theory based calculations performed on a model molecule of the complex. We show that the calculated partial density of vibrational states based on the structure of a single iron(II) center which is linked by three pyrazole rings to borat is in good accordance with the experimentally obtained ⁵⁷ Fe-pDOS and assign the molecular vibrations to the prominent optical phonons.
 
Article
Analysis of the available experimental data on iron compounds has shown the following: The ⁵⁷Fe Mössbauer isomer shift (IS) depends on the average interatomic distance between the iron ion and the ions of its first coordination sphere (aID), on the chemical nature of these ions, and also on the iron coordination number. An increase in aID and a decrease in the coordination number lead to an increase in IS. For a given polyhedron, the correlation between IS and aID is close to linear with a slope of about 0.04 mm⋅s⁻¹⋅pm⁻¹. A change in the oxidation state of iron (OSFe) affects IS, since a change in OSFe causes a change in aID due to a change in the number of electrons on the valence shell of iron; the more OSFe, the less IS. If the aID of differently charged ions are close (e.g., for the pair H4[Fe(CN)6] and H3[Fe(CN)6]), then the IS values do not differ significantly. A change in the spin state of an iron ion affects IS insofar as this change causes a change in aID. In particular, the transition from the high-spin to the low-spin state in iron(II) spin-crossover compounds leads to a decrease in aID and, accordingly, to a decrease in IS. A change in the spatial structure of the iron coordination polyhedron may affect IS. This was observed when comparing tetrahedral and square-planar iron(II) oxygen polyhedra. The tetrahedral and square-planar oxygen polyhedra of high-spin iron(II) show increased IS values. In terms of the orbital model of the electron shell of the atom, the above data can be explained by the interactions of the 4s-orbital of iron with its other valence orbitals (undergoing hybridization), as well as with the orbitals of the ions surrounding iron (establishing directional chemical bonds). These interactions affect the electron density at the iron nucleus. The corresponding contributions depend on the distances between the iron ion and the ions surrounding it, but do not depend on the number of orbitals involved into hybridization or on the number of directional chemical bonds. The electron shell of each ion of the iron polyhedron also makes an additional (non-bonding) contribution to the electron density at the iron nucleus. In some specific cases (e.g., for iron in noble gas matrices), the observed unusually low IS can be explained by the filling of the 4s-orbital of iron with its valence non-bonding electron(s).
 
SEM micrographs and EDX analysis of iron oxide waste scale obtained by rolling mill steel industry and after annealed at 1000 °C. a) and (b) micrographs of the collected scale samples and (c), (d) micrographs for the annealed sample at 1000 °C. (e) and (f) EDX for raw sample and after annealing at 1000 °C
Xray Diffractogram of iron oxide waste scales obtained by rolling mill steel industry and after annealing at 1000 °C
Magnetic responses of iron oxide waste scales obtained by rolling mill steel industry (a) M(T), (c) M(H) for the raw sample, (c) M(T) and (d) M(H) for the sample annealed at 1000 °C
Room Temperature Mössbauer of iron oxide waste scales obtained by rolling mill steel industry (top) and after annealed at 1000 °C (bottom)
Article
Every year, the steelmaking industry produces millions of tons of slags resulting in pollution to the environment. Among the waste, secondary metals and scales rich in iron oxides are also thrown away. There is a need to treat the steel waste in a reasonably way to protect the environment and proposing new cheap technologies for producing advanced materials. In this study we report the morphological and structural characterization of waste scales generated during roll milling steel process at JSC “Arcelor Mittal Temirtau”. The raw slag and annealed at 1000 °C were measured by X-ray diffraction (XRD), scanning electron microscopy adapted with energy dispersive X-ray (SEM- EDX), magnetometry and Mössbauer Spectroscopy (MS). Fe and O were detected by EDX as main chemical elements and Si, S, Ca, Mg, C and Al as minimal elemental composition. XDR for the raw sample revealed α-Fe 2 O 3 (hematite) and Fe 3 O 4 (magnetite) as principal and secondary phase, respectively; whereas monophasic α-Fe 2 O 3 is detected for the scales annealed at 1000 °C. Magnetometry measurements show the Verwey transition for the raw sample and the Morin transition for the annealed at 1000 °C; those are fingerprints for the presence of magnetite and hematite, respectively. MS measurements for the raw sample consist of 6 small peaks of absorption and a broad two-lines absorption peak in the central part. The doublets are associated to the hyperfine parameters belonging to wustite. Magnetite is related to the hyperfine parameters for two sextets in octahedral Fe 2.5+ and tetrahedral Fe ³⁺ sites and a small sextet that resembles the Mössbauer parameters of α-Fe 2 O 3 . Only a well crystallized and weakly ferromagnetic sextet confirm the presence of α-Fe 2 O 3 phase for the sample annealed at 1000 °C due to thermal oxidation.
 
Article
The ⁵⁷Fe Mössbauer spectrum obtained after ⁵⁷Mn (T1/2 = 1.45 min) implantation of solid hydrogen was measured at 7 K. The spectrum was analyzed as three components, and the chemical species of each component was assigned from the obtained Mössbauer parameters and the results of density functional theory (DFT) calculations. The formation process of chemical species and the oxidation states of Fe atoms produced by β– decay of ⁵⁷Mn are discussed considering the charge transfer process, in relation to previous emission Mössbauer spectroscopy experiments with ⁵⁷Co implantation of solid hydrogen at low temperature.
 
a and b Ladle furnace slag remanent and demetallized, c and d SEM micrography and color mapping for remanent and demetallized slag, e and f EDX sum spectrum and g and h X ray fluorescence of remanent and demetallized ladle furnace slag.
X-ray diffractogram of metallurgical slag produced in a ladle furnace during steelmaking process in SIDERPERU plants. a) remanent slag, b) demetallized slag
Magnetization response as a function of the temperature for the remanent (a) and demetallized (b) slags collected from SIDERPERU steel plant
Mössbauer spectra at RT of a slag produced in a ladle furnace during steelmaking process in SIDERPERU plant
Article
The steel industry produces large amounts of slag coming from different stages during the steelmaking process every year. Currently, there are numerous attempts to recycle it or to use it in some other industry sectors and to preserve the environment. The characteristics of the slag depends on the steelmaking process and it is crucial to have it before any attempt of recycling. In this work, slag sample produced in the ladle furnace from SIDERPERU steel plant were collected and analyzed by using energy dispersion X-ray (EDX), X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), SQUID magnetometer and Mössbauer spectroscopy. The chemical analysis obtained by EDX and XRF indicate that the main elemental composition of the material is Fe, Ca, Si and Cr. XRD identifies that these elements are in the phases: FeO, Fe3O4, α-Fe2O3, Ca2SiO4, and Ca2,32Mn0,68SiO7. Magnetometry measurements suggest the Verwey transition for magnetite and the Morin transition for hematite are screened by the presence of superparamagnetic phases. The Mössbauer spectrum shows two doublets related to Fe²⁺ and Fe³⁺ ions with hyperfine parameters belonging to that of non-stoichiometric wustite. Also, the presence of hyperfine fields characteristic of the Fe3O4 and Fe2O3 phase identified at room temperature verifies the magnetometry analysis. The analysis of the sample used in this work reveals details connected with the steel fabrication processes and are helpful for posterior recycling attempts.
 
Article
Nowadays there is a high interest in the recovery of industrial steel waste into useful by-products. For that purpose, it is important to know the physical and chemical properties of steel slag in order to better understand its characteristics and thus seek applications. In this work, we study primary steel slag formed in an electric arc furnace (EAF). Here we present the structural characterization and magnetic properties of the slag performed by X-ray fluorescence spectroscopy (XRF), X-ray diffractometry (XRD), scanning electron microscopy (SEM), magnetic measurements and Mössbauer spectroscopy. The elements Zn, Fe, Cl, Ca, and K and the phases Fe3O4, Zn5(OH)8Cl2.H2O, ZnO, and KCl were identified by XRF and XRD, respectively. Mössbauer spectroscopy at room temperature shows one doublet typical for Fe²⁺, and sextets corresponding to Fe3O4, and Fe2O3. ⁵⁷Fe-Mössbauer spectroscopy appears as a necessary tool in metallurgical slag research.
 
Article
A new experimental method to search for T-violating transverse muon polarization (PT\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$P_T$$\end{document}) in the K+→π0μ+ν\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$K^+ \rightarrow \pi ^0 \mu ^+ \nu$$\end{document} decay has been proposed. In this new experiment, the measurements of the μ+\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mu ^+$$\end{document} momentum vector, the π0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pi ^0$$\end{document} momentum vector, and the μ+\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mu ^+$$\end{document} polarization will be performed by the same electro-magnetic calorimeter. One of main issues is the choice of a scintillation material which can preserve the μ+\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mu ^+$$\end{document} spin polarization for several μ+\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mu ^+$$\end{document} lifetimes. A test experiment to measure the μ+\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mu ^+$$\end{document} polarization in various scintillating crystals was performed at J-PARC Material and Life Science Facility (MLF). We concluded that the μ+\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mu ^+$$\end{document} polarization in CeF3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_3$$\end{document} is high enough to perform the new T-violation experiment.
 
Article
We present imaging techniques in Mössbauer spectroscopy for an operando measurement of pattern formation in materials, i.e., (1) mapping by focused γ-ray and (2) direct imaging by a CMOS camera combining with the mapping system after converting γ-rays to visible light with a scintillator. From the viewpoint of image processing, mapping interval and Gaussian smoothing are discussed to obtain contour maps. We also present typical images of surface corrosion and magnetic domains of ⁵⁷Fe foil, comparing the resolution and the measuring time for both imaging techniques.
 
Gibbs free energy (a) and enthalpy change (b) of the reactions occurred during the carbothermal reduction process of black slags formed in an electrical arc furnace during industrial steelmaking
HRB335 steel rod elaborated from the reduced powder obtained after the carbothermal reduction of the black slag (a), Photography of the recycled HRB335 steel chips and a microscope image taken at 40× magnification (b), XRF spectrum of the HRB335 steel chips (c)
Mössbauer parameters of the black slag samples before and after the carbothermal reduction pro- cess.
Article
The primary process in an electrical arc furnace (EAF) during industrial steelmaking results in tons of black slags which cause pollution to the environment. In this work, the iron oxides of black slags generated in the EAF from the SIDERPERU plant, Peru was reduced via the carbothermal reaction. The reduction of the black slag to α-Fe is demonstrated by X-ray diffraction, Mӧssbauer spectroscopy and magnetometry. However, phases with calcium and silicon persist in the sample after the carbothermal process. The thermodynamic calculations of the most probable reactions sequence were performed to understand the reduction process. The magnetometry measurements confirm the presence of ferromagnetic domains, supporting the success of the reduction of the black slag to α-Fe. The reduced black slags were recycled into a HRB335 steel rod by consolidation and extrusion processes and inspected by X-ray fluorescence.
 
Article
This work reports honey green synthesis of MgxZn1-xFe2O4 (x = 0.0–1.0) spinel nano ferrite (grain diameter: 25.3 nm- 33.4 nm) by sol–gel auto-combustion method. Thermally treated samples at 550 °C for 3 h, were characterized by x-ray diffraction, ‘XRD’ scanning-electron-microscopy-energy-dispersive-x-ray-spectroscopy ‘SEM-EDS’, Mössbauer spectroscopy operating at 5 K with/without 5 T magnetic field. XRD confirms spinel phase formation, and presence of α-Fe2O3 (1.1–4.2%), while EDS confirms the uniform allocation of all the elements present in the studied samples. Agglomerated nano-particles are seen in SEM images. Increasing Mg-content: i) alters structural properties, ii) leads to modification of cationic population on A, B site, iii) affects A–O–A, B–O–B, A–O–B super-exchange interaction, and iv) shows linear decrease of Néel magnetic moment. Mössbauer results confirms 3+ state of Fe, and changes in local environment around Fe3+ ion induced modification of super-exchange interaction, reflected in internal hyperfine field. Finite canting angle suggests the applicability of Yafet-Kittel (Y-K) three sub-lattice model in describing magnetic behavior of the studied samples. Due to the presence of α-Fe2O3 in the studied samples, difference is observed in the inversion parameter, obtained from XRD, and Mössbauer data.
 
IR-spectra of [Fe(Diethyl-Diox) 3 (BOH) 2 ] (top), [Fe(Diethyl-Diox) 3 (BOEt) 2 ] (bottom)
MS-spectrum of [Fe(Diethyl-Diox) 3 (BOH) 2 ]
Article
Dioximes as ligands are used as analytical reagents and serve as models for biological systems as well as catalysts in chemical processes. A number of novel mixed complexes of the type [Fe(DioxH) 2 (amine) 2 ] have been prepared and characterised by FTIR, ⁵⁷ Fe Mössbauer and mass spectroscopy by us. We have found strong Fe–N donor acceptor interactions and iron occurred in low-spin Fe II state in all complexes. Later, we have also found that the incorporation of branching alkyl chains (isopropyl) in the complexes alters the Fe–N bond length and results in high-spin iron(II) state [1, 2]. The question arises: can the spin state of iron be manipulated generally by replacing the short alkyl chains with high volume demand ones in Fe-azomethine-amine complexes? To answer the question we have synthetized novel iron-bis-glioxime and iron-tris-gloxime complexes when long chain alkyl or aromatic ligands replaced the short alkyl ones and studied by ⁵⁷ Fe Mössbauer spectroscopy, MS, FTIR, UV-VIS, TG-DTA-DTG and XRD methods. Novel iron-bis-glyoxime and iron-tris-glyoxime type complexes, [Fe(Diethyl-Diox) 3 (BOH) 2 ], [Fe(Diethyl-Diox) 3 (BOEt) 2 ] and [Fe(phenyl-Me-Diox) 3 (BOEt) 2 ], were synthesized similarly as described in [2]. The FTIR, UV-VIS, TG-DTA-DTG and MS measurements indicated that the expected novel complexes could be successfully synthesized.
 
Article
From low temperatures through the Curie temperatures, the phonon density of states (DOS) was measured for bcc ⁵⁷Fe, and the partial phonon DOS was measured for cementite, ⁵⁷Fe3C, by nuclear resonant inelastic x-ray scattering (NRIXS). Nuclear forward scattering (NFS) was used to determine the state of magnetization of ⁵⁷Fe3C. The changes in phonon DOS with magnetization were assessed, and a linear relationship was found between the temperature dependences of the magnetization and the non-quasiharmonic shifts of phonon frequencies. Following the quasiharmonic approximation (QHA) for non-harmonic phonons, a magnetic quasiharmonic theory is developed to account for how phonon frequencies are altered by changes in magnetization. The formalism explains well the discrepancy between the free energy measurements and predictions of the QHA for both bcc iron and cementite. The physical origin of the magnetic Grüneisen parameters remains a challenge.
 
Article
Single-phased Ru3+-doped LaFeO3 nanocrystalline particles (6-70 nm), with nominal compositions of LaFe1-xRuxO3 (x = 0.00, 0.015, 0.03, 0.05 and 0.08), were prepared using mechano-synthesis at temperatures that are ca. 400 °C- 700 °C lower than those used to synthesize cation-doped LaFeO3 conventionally. The Ru3+ ions are found to substitute exclusively for the Fe3+ ones at the octahedral sites of the perovskite-related structure. The lattice parameters of all samples are suggestive of a weak Jahn-Teller-like distortion as opposed to the normal distortion of orthorhombic perovskites. 57Fe Mössbauer measurements for all samples show the Fe3+ ions to be in high-spin state implying that the observed lattice distortion is due to particle-size surface-induced disorder rather than the electronic degeneracy associated with the normal Jahn-Teller distortion. The decrease in the Mössbauer hyperfine magnetic fields with increasing Ru3+ content is attributed mainly to particle size reduction rather than the cationic substitution of Fe3+ by the Ru3+. A monotonic decrease of the optical band gap from 2.17 eV (x = 0.00) to 1.79 eV (x = 0.08) was observed, revealing how doping with Ru3+ affects the optical absorption of the LaFeO3 nanoparticles.
 
Article
We present the magnetic, structural and ⁵⁷Fe Mossbauer characterization of soils collected from an ancient mercury contaminated city named Huancavelica in Peru. The characterization results indicate that silicates and carbonates are the main mineralogical constituents in the samples. In addition, ⁵⁷Fe Mössbauer spectra at room temperature reveal, the presence of two components: a magnetic component related to magnetic Fe-oxides (magnetite, hematite, goethite) and a high non-magnetic component related to Fe⁺³ in high spin configuration and tetrahedral coordination in silicates. The magnetization measurements present screening of paramagnetic, ferromagnetic and antiferromagnetic signals, typical from soils containing different silicates and iron minerals. Remarkably the Verwey and Morin transitions corresponding to magnetite and hematite, respectively, are screened by the paramagnetic signal corresponding to the major silicate components in the samples. Overall, the soils are mainly composed of crystalline and amorphous silicates, calcites and iron bearing which are typical from Andean soils.
 
Article
We have developed a new and compact β-nuclear magnetic resonance (NMR) system using beta-radioactive nuclei. By using a Halbach array permanent magnet to create a static magnetic field, and a scintillating fiber as a detector, we succeeded in significantly reducing the size and weight of the entire system. The performance of the new spectrometer was tested and evaluated by observing an NMR spectrum of ¹⁹O (T1/2 = 26.9 s, I = 5/2) in TiO2.
 
Article
A GaN thin film grown on sapphire substrate was implanted with ⁵⁷Fe and ⁵⁶Fe ions with energies of 60 keV, 160 keV and 370 keV and fluences selected to achieve a homogeneous concentration profile of approximately 2.6 at. % in the film. Implantation induced lattice damage was tracked with conversion electron Mössbauer spectroscopy (CEMS) after annealing the sample up to 900 °C. The spectral component due to Fe in lattice damage shows significant decrease on annealing above 700 °C, accompanied by a corresponding increase in the paramagnetic doublet component attributed to Fe substituting Ga in the wurtzite GaN lattice (FeGa). After annealing at 900 °C, FeGa accounts for 75% of the spectral area, in good agreement with the substitutional FeGa fraction (80%) observed in emission channeling measurements on Fe implanted into GaN at extremely dilute concentration.
 
Article
Cluster radioactivity is one of the exotic phenomena which offers an alternate emission in heavy and superheavy nuclei in addition to the α-decay and spontaneous fission. In the present work, we predict half-lives of cluster decay in superheavy nuclei 294,296Og by picking up the emission of all possible even-even isotopes from He to Mo (Z = 2-42). These half-lives are compared with the half-lives of α-decay, and accordingly the possibility of most probable cluster emission is ascertained. For these decay processes, the disintegration energies (Q-values) are taken from WS4 mass model. To estimate cluster emission half-lives, we use few widely known empirical formulas i.e. Horoi [J. Phys. G: Nucl. Part. Phys. 30, 945 (2004)], RenA [Phys. Rev. C 70, 034304 (2004)], NRDX [Phys. Rev. C 78, 044310 (2008)], UDL [Phys Rev. 103, 072501 (2009)], and UNIV [Phys. Rev. C 83, 014601 (2011)]. The emission of 86,92Kr from 294Og and 88,92Kr clusters from 296Og are found to be the dominant clusters. Details of this study will be certainly useful for future experiments eyeing on synthesis of new elements.
 
Article
We report the Mössbauer spectra using circularly polarized synchrotron-radiation beams for the Fe/Au interface. For the interfacial studies in multilayers, the doping of 57Fe into the thin Fe layer enables to probe the interfacial electronic and magnetic structures. Here, the Mössbauer spectroscopy using linearly or circularly polarized synchrotron-radiation beam for Fe/Au interface clarifies the local environments around the Fe atoms in a thick Fe layer with in-plane magnetization, which is compared with the case of perpendicularly magnetic anisotropy (PMA) presented by the previous report [J. Okabayashi et al., Phys. Rev. B 103, 104,435 (2021)]. Contrary to the PMA case, the present sample exhibits bulk-like Mössbauer spectra. The spectral characteristics can be explained by diffusive Fe atoms around the Fe/Au(111) interface while the interfacial charge transfer and electric-field gradient are elucidated.
 
Article
The Johari-Goldstein-(JG)-β process dominates some of the mechanical properties of polymeric systems. We studied the JG-β dynamics in a rubber nanocomposite, which is a model system of tire rubber, by quasi-elastic scattering experiments using time-domain interferometry. We observed that the time scale of the local motion of the polymer chain started to decouple from the time scale of the chain diffusion motion on cooling in deeply supercooled region. The temperature dependence of the local relaxation time follows the Arrhenius law down to the glass transition temperature. The JG-β process dominates the local polymer dynamics in the polymer nanocomposite system around the glass transition temperature, similar to the case of the neat polybutadiene system. The time scale of the JG-β process in the polymer nanocomposite system was two times longer than that of the neat polybutadiene system. These results suggest that the presence of silica nanoparticles slows down JG-β relaxations and provides a new clue for understanding the mechanical relaxation properties of polymeric products from a microscopic viewpoint.
 
Article
We apply high energy mechanosynthesis in mixtures of Y2O3 and Fe2O3 to form activated nanostructured oxide composites for subsequent temperature treatment with the aim to synthesize single phase functional Y3Fe5O12 garnet particles. Obtained at the same temperature regime but starting from structurally different precursors, garnet particles demonstrate different magnetic behavior. Mossbauer and Raman spectroscopy were applied for a comprehensive characterization on the local atomic scale the influence of the mechanochemically produced precursor’s fine structure formed at different activation duration on the structural and magnetic state of the garnet particles. X-ray diffraction and visualization of fine particles structure by SEM microscopy were supplemented. An intermediate disordered iron oxide phases and orthoferrite YFeO3 rather garnet structure formation at prolonged duration of intense mechanical activation was determined. Magnetic structure of Y3Fe5O12 formed after annealing was dependent on the degree of the oxides interaction in precursors and defects concentrated at the grain boundaries and interfaces. Both applied spectroscopies showed complementary insight into the nature of the local structural disorder at the steps of mechanosynthesis to the mechanism of fine garnet structure formation.
 
Article
The literature on effects of time-dependent hyperfine interactions on perturbed angular correlation (PAC) spectra is dominated by analyses based on models of stochastically fluctuating interactions. The Floquet formalism offers a convenient alternative analysis when interactions have a harmonic time dependence. This is demonstrated in the present work through simulation of PAC spectra due to uniformly rotating electric field gradients (EFGs). Physically, this situation would arise when PAC tracers are embedded in molecules with inertial rotation velocities much larger than molecular collision rates, in which case reorientation of rotation axes would be negligible on the characteristic PAC timescale. The prospect for using PAC to study inertial properties of molecules is explored through simulations with molecules modeled as symmetric, rigid bodies.
 
Amount of ferrosilite (Fs) in orthopyroxenes versus amount of fayalite (Fa) in olivines obtained for 4712 ordinary chondrites -the values are taken from Koblitz 2012 [3]
Mössbauer spectra of meteorites Buzzard Coulee, Mreïra, Mahbas Arraid obtained at room temperature
Mӧssbauer parameter obtained for meteorites: Buzzard Coulee, Mreïra and Mahbas Arraid
The percentages of Mössbauer spectral areas [%] associated with olivines (ol), pyroxenes (pyr), metallic phases (met) and troilite (tr) obtained in three ordinary chondrites: Buzzard Coulee, Mreïra, Mah- bas Arraid
Article
4M method is a new application of Mössbauer spectroscopy to quantitative classification of ordinary chondrites. 4M derives from four words: meteorites, Mössbauer spectroscopy, multidimensional discriminant analysis, Mahalanobis distance. This method was published by us in 2019. In this paper we present application of 4M method to classification of four meteorites. Link to script with calculation needed for classification of ordinary chondrites was given.
 
Article
GdFexMn1-xO3 (x = 0.0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0) nanoparticle series was synthesised using sol–gel auto-combustion technique. Rietveld refinement of x-ray diffraction (XRD) patterns revealed that all samples are crystallized in a single phase with (Pnma) space group No.62. The FC–ZFC measurements showed an increase in the antiferromagnetic (AFM) to paramagnetic (PM) transition Néel temperature (TN) with the increase of Fe³⁺ content, reaching a value of 344 K at 50% of Fe doping. The inclusion of Fe also induced spin reorientation temperature (TSR) at x = 0.5 and x = 0.7. ⁵⁷Fe mössbauer spectroscopy measurements were carried out at room temperature (RT⁓295 K) and liquid nitrogen (LN⁓78 K) temperature. Both RT and LN mössbauer spectra were fitted with paramagnetic doublet for low Fe content (x < 0.5), whereas for higher Fe content (x > 0.5), the spectra were fitted with magnetic sextet. Isomer shift values confirms the dominance of Fe in its high oxidation state (Fe³⁺).
 
Article
Tons of waste is produced during iron steel’s industrial production, creating environmental pollution. This work aims to characterize the steel scale formed on the billet surface during the last step of steel production in the SIDERPERU steel plant. Scanning Electron Microscopy (SEM) shows stacked layers one above the other on steel billets scales surface. Energy Dispersive X-ray (EDX) and X-ray Fluorescence (XRF) reveal the high content of Fe and O, with Ca, Si, Mn, and Cr as minority elemental compounds. X-ray Diffraction (XRD) shows FeO, α-Fe2O3 and Fe3O4 as crystallographic phases. Magnetometry reveals Verwey transition and paramagnetic signals that screen the Morin transition. Mössbauer Spectroscopy at room temperature displays magnetic and non-magnetic parts. The non-magnetic part has the hyperfine parameters corresponding to predominant nonstoichiometric wustite. Octahedral (Fe⁺²/Fe³⁺) and tetrahedral Fe⁺³ hyperfine fields of 46.0 and 49.4 T values respectively are associated to nonstoichiometric magnetite and another sextet with a hyperfine field of 52.0 T is related to hematite.
 
Article
We report sol gel auto-combustion synthesized CoCrxFe2-xO4 (x = 0.0 − 1.0) spinel ferrites, and use x-ray diffraction ‘XRD’, magnetic measurements, and Mössbauer spectroscopy to study the effect of Cr-content on their structural properties, magnetic properties, and correlation between them. Formation of single-phase nono spinel ferrite (grain size: 18.1 – 46.6 nm), is confirmed by XRD. Results show that with increasing Cr-content, lattice parameter decreases, and Cr3+ ions remain more populated on B-site, whereas Co2+ ions remains almost equally populated on both A, B site, show lower disorder, and modification of A–O − A, B– O − B, A–O − B super-exchange interaction. For Cr-content ≥ 0.75, Mössbauer measurements show presence of a non-magnetic doublet, and isomer shift values confirm that Fe has 3 + oxidation state. Observed structural changes, lead to reduction of saturation magnetization, coercivity.
 
Article
The local structure around iron atom is important to show spin-crossover phenomenon in the assembled Fe(II) complexes. In the present study, the low symmetry bridging ligand, 2,6-diethyl-bis(4-pyridyl)benzene (2,6-debpb) (A-B type ligand) was synthesized. And the assembled Fe(II) complexes, [Fe(NCX)2(2,6-debpb)2]n (X = S, Se, BH3), were synthesized. [Fe(NCS)2(2,6-debpb)2]n showed the temperature independent high-spin state, while small amount of low-spin state was observed in 57Fe Mössbauer spectrum at 78 K for [Fe(NCX)2(2,6-debpb)2]n (X = Se, BH3). Magnetic susceptibility measurement supported the 57Fe Mössbauer results. X-ray structural analysis for [Fe(NCBH3)2(2,6-debpb)2]n revealed that the local structure around iron atom is distorted, disturbing the approach of the ligand to iron atom not to show complete spin-crossover phenomenon. The local structure is FeA2B2 type and there was no disorder in the bridging ligand.
 
Mӧssbauer spectra of two samples of the Bjurböle meteorite
Plot of the spectral areas of (metallic phases + troilite) vs spectral area of (olivine + pyroxene) for ordinary chondrites type H, L, LL and analysed samples
Plot of the spectral areas of (olivine + pyroxene + troilite) vs spectral area of metallic phases for ordinary chondrites type H, L, LL and analysed samples
Article
Mössbauer spectra of nonweathered ordinary chondrites consist of four main mineral phases: olivines, pyroxenes, metallic phase and troilite. These minerals represent more than 95% of the whole mass of an ordinary chondrite. Distribution of these mineral phases in micro-scale is not homogeneous. Nevertheless, preparation of representative sample of ordinary chondrite for Mössbauer measurements is possible. To do that a part of 1 g nonweathered material, selected from inside of meteorite without any specific intention is needed. The Warsaw group has been working on investigation of meteorites for 25 years and has analysed about 150 Mössbauer spectra of various meteorites. Among them we found 15 spectra, which could be suspected of being non-representative. These spectra were obtained from Baszkówka, Amber, Bjurböle, Krasnoi-Ugol and Chelyabinsk meteorites. The analysis of how the samples of meteorites were selected for investigation, has shown that the non-representativeness of samples may be due to: intentional choice of sample, preparation of sample from a too small part of material or the use of non-credible source of meteoritic samples. For confirmation of these assumptions, we used a new method of classification of ordinary chondrites – the 4M method. It turned out that this method is a very useful tool for investigation of non-representative samples of equilibrated ordinary chondrites.
 
Article
Nuclear magnetic resonance (NMR) spectrum of the short-lived nucleus 17N (I = 1/2, T1/2 = 4.17s) in liquid water was measured by means of the β-NMR technique to clarify the chemical species formed by nitrogen ions injected into water. We have improved the spectral resolution to 5ppm in the full width at half maximum which is about 1/40 times compared to the previous study. The shape of the obtained spectrum indicated that it may consist of multiple resonance lines rather than a single line. Some possibilities regarding the chemical states of nitrogen in water are discussed based on the present result.
 
Article
The magnetic properties of magnetite nanoparticles (Fe 3 O 4 NPs) strongly depend on their chemical and physical parameters, which can be regulated by a controlled synthesis process. To improve the quality of the obtained nanoparticles, their surface is often modified with organic compounds (from the group of surfactants, sugars, proteins, or organic acid). In this study, we synthesized magnetite nanoparticles with a surface modified with the organic compound DMSA. Then, the nanocrystallites were characterized in terms of structure and morphology. To investigate the role of DMSA and to understand the adsorption mechanism, FTIR measurements were carried out. Using Mössbauer spectroscopy, we investigated temperature-induced changes in the magnetic properties of prepared samples. The spectra were recorded in a wide temperature range (from 4 K to 390 K) for two types of samples: powders and ferrofluids with various concentrations. In the case of powder samples, the superparamagnetic doublet appeared at room temperature. For magnetic suspensions, the spectra were more complicated. They consisted of superposition of asymmetrically broadened sextets and doublets, which was caused by the occurrence of long-range dipole-dipole interactions. These interactions affected the magnetic properties of the material and increased the blocking temperature. Additionally, the magnetic hysteresis and zero field cooling-field cooling (ZFC/FC) curves were measured with the use of a vibrating sample magnetometer.
 
Article
Spin pumping is an interfacial spin current generation from the ferromagnetic layer to the non-magnetic metal at its interface. The polarization of the pumped spin current \(\mathbf {J}_s \propto \mathbf {m}\times \dot{\mathbf {m}}\) depends on the dynamics of the magnetic moment \(\mathbf {m}\). When the materials are based on light transition metals, mechanism behind the spin current transfer is dominated by the exchange interaction between spin of localized d-electrons and itinerant conduction electrons. In heavier transition metals, however, the interaction is not limited to the exchange interaction. The spin of the conduction electron can interact to its nuclear spin by means of hyperfine interaction, as observed in the shift of NMR frequency. By studying the spin polarization of conduction electron of the non-magnetic metallic layer due to a nuclear magnetic moment \(\mathbf{I}\) of the ferromagnetic layer, we show that the hyperfine interaction can mediate the spin pumping. The polarization of the spin current generation is shown to have a similar form \({J}_s\propto \mathbf {I}\times \dot{\mathbf {I}}\).
 
Article
The spin-lattice relaxation times T1 of an unstable nucleus 19O (T1/2 = 26.9 s, I = 5/2) implanted into Y2O3 stabilized ZrO2 (YSZ), which is a solid oxide fuel cell material, were measured at T = 278 − 333 K by means of the β-NMR technique, using a highly spin polarized 19O beam produced via the heavy ion reaction. The motional correlation times τc for oxygen motion derived from the T1 data are on the same straight line on the Arrhenius plot as those derived from the previous 17O-NMR data at above the room temperature. This indicates that 19O ions implanted into YSZ from outside seem to exhibit the same behavior as oxygen ions in the host YSZ material.
 
Article
Mössbauer Spectroscopy is an important analytical technique, which allows studying electromagnetic parameters of the target atom surroundings. It is thus possible in the studied samples to identify the different material phases, crystalline structures, valence states, magnetic properties, etc. Mössbauer spectroscopy is commonly used especially for studying new and highly functionalized iron-based materials and nanomaterials. As these are usually cutting-edge scientific studies, it is often required to customize the experimental setups too. This would not be possible without top equipment and long-term experience. For this reason, we have been developing and improving Mössbauer spectrometers in our laboratories for 30 years [Pechousek et al. in AIP Conference Proceedings 1489:186–193, 2012] in order to support our scientific work with the most advanced, precise and user-friendly Mössbauer instruments. This paper deals with the advancement in their design, focusing on the enhancement of the velocity drive and its weak point.
 
Article
Fe-Gd amorphous thin films of different compositions and thicknesses were analyzed with respect to their magnetic and magneto-optical behavior. By preparing samples with the same Fe/Gd elemental ratio at different thicknesses, and of various Fe/Gd ratios at constant thickness, respectively, we were able to show the influences of these two parameters on the interconnected behavior of the two magnetic sub-lattices, one of Fe and the other of Gd, which are antiferromagnetically coupled. Magneto-Optical Kerr Effect (MOKE) measurements revealed reversed hysteresis loops for sample compositions crossing the magnetic compensation point. Temperature dependent magnetization curves highlighted the variation of the overall net contribution of the two magnetic sub-lattices by changing either the Fe/Gd elemental ratio or the film thickness. 57Fe Conversion Electron Mössbauer (CEM) spectra give additional support to the specific magnetic behavior evidenced by temperature and field dependent Superconducting Quantum Interference Device (SQUID) magnetometry.
 
Article
We applied the small angle nuclear scattering of synchrotron radiation (SANRS) to investigate anisotropic Galfenol-polyurethane composite comprising Galfenol grains with Fe57 nuclei arranged in the parallel chains surrounded by the non-resonant polymer substance. We aimed to insight into the individual magnetic structure of the particles and particles/polymer interface using the ability to align the synchrotron radiation beam directly on the particle by reducing the analyzed volume and resonant thickness of the composite sample. The size of the studied particles was about 3–7 μm. The results of precise analysis of the rocking curves for electron and nuclear response let to support explanation of the functional composite properties.
 
Article
Fe oxide magnetic nanoparticles (MNPs) in general and cobalt ferrite nanoparticles in particular have immense potential for applications in catalysis, medicine, information and energy storage, etc. MNPs feature interesting physical and chemical properties, different to those of corresponding bulk materials. The magnetic anisotropy constant of almost spherical CoFe2O4 MNPs is much higher than that of magnetite (Fe3O4) MNPs of similar geometrical parameters due to the magnetocrystalline contribution. CoFe2O4 shows significant magnetization at saturation, high coercive field and Curie temperature, and good chemical and magnetic stability, being therefore preferable to the most usual Fe3O4 MNPs. A surfactant-assisted synthetic route was employed to synthesize Fe oxide and in particular cobalt ferrite MNPs over a wide pH range (3–13), endeavor which allowed analysis of transient and parasitic phase identified in acidic reaction conditions.
 
Article
The influence of Fe-doping on the structural and magnetic properties of NdFexMn1- xO3 (x = 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0) nanoparticles was investigated. Auto-combustion sol-gel technique was used to synthesize the compounds. X-Ray diffraction refinement indicated that all samples were formed a single-phased orthorhombic structure with Pbnm space group. The M-T curves measurements at an applied magnetic field of 0.2 T demonstrated that all compounds undergo antiferromagnetic (AFM) to paramagnetic (PM) transition as the temperature increased in which the Nèel temperature was observed below ⁓10 K for all compounds except for NdFe0.3Mn0.7O3 compound (62 K). 57Fe transmission Mӧssbauer spectra were measured at room temperature (295 K) and liquid nitrogen temperature (78 K) for all compounds. The magnetic ordering of these compounds was highly dependent on iron content. The compounds with low iron concentration at 295 K and at 78 K were characterized by a dominant paramagnetic high-spin Fe3+ doublet. The hyperfine magnetic field distribution was responsible for the broadening of the magnetic sextet of the room temperature Mӧssbauer spectrum with x = 0.7. The 57Fe Mӧssbauer spectra with higher iron dopingat both 295 K and 78 K demonstrated well resolved magnetic sextet with a hyperfine magnetic field increased linearly with increasing x.
 
Article
In the present work, polycrystalline Y-type Ba0.5Sr1.5Co2−xZnxFe12O22 (X = 0, 0.5, 1 & 2) hexa-ferrites prepared by the sol-gel auto combustion method are investigated by x-ray diffraction (XRD), 57Fe Mössbauer spectroscopy (MS) and magnetization measurements. XRD data confirms the single-phase formation for x = 0 and 0.5; however, with further increase in Zn concentration secondary phases are observed. The in-field Mössbauer data measured at low temperature (5K) indicates that there is a re-distribution of Fe3+ ions in the studied samples, with the substituted Zn2+ preferentially going to 6CIV, 6CIV ∗ sites.
 
Article
The results of the iron state testing in selected outdated pharmaceuticals by Mössbauer spectroscopy are presented. Pharmaceuticals containing ferrous sulfate and ferrous fumarate demonstrate appearance of small content of ferric compounds and some instability of ferrous sulfate and ferrous fumarate with formation of ferrous compounds. In contrast, pharmaceutical products containing iron chelates show high instability of iron chelates with formation of ferric compounds even in fresh samples with further increase of their content with aging. Iron-polymaltose complexes containing β-FeOOH nanosized cores demonstrate a good stability after expire date.
 
Article
In this work Fe3O4:Er nanoparticles (NPs) with the characteristic size of ~ 11 nm were synthesized via classic co-precipitation method. Electron microscopy and X-ray diffraction were employed to probe the morphology and structure of the samples. Results revealed that samples synthesized in the Fd-3mZ structure with lattice constant close to that of pure magnetite. 111In probe generator was incorporated at synthesis in order to map the evolution of hyperfine magnetic field with temperature using time differential perturbed angular correlation (TDPAC) spectroscopy. The TDPAC results are discussed in terms of the effect of Er dopant on the magnetic properties and local structure of the NPs.
 
Article
Surface magnetism of Fe (001) was investigated by the in situ iron-57 probe layer method with a synchrotron Mössbauer source. The observed layer-by-layer internal hyperfine field shows a marked reduction at the surface and an oscillatory behavior with increasing depth in the individual layers below the surface. The calculated layer-by-layer hyperfine interactions (hyperfine field, isomer shift, and quadrupole shift) were consistent with the experimental results. The results give direct evidence for the magnetic Friedel oscillations, penetrating several layers from the Fe (001) surface.
 
Article
The present work reports the in-field 57Fe M\(\ddot {o}\)ssbauer spectroscopy measurements on polycrystalline R3Fe5O12 (RIG, R=Y, Gd, Ho, Tm, & Yb) rare-earth iron garnets. The contrast between the effective hyperfine field (Heff) values of two Fe3+ sites (tetrahedral, d- and octahedral, a- sites) across magnetic compensation (TComp) facilitates to probe the Fe3+ sublattice spin reversal in RIG systems (R=Gd, Ho and Yb) exhibiting magnetic compensation. Further, the analysis of relative intensity of absorption lines in a sextet from the field dependent 57Fe M\(\ddot {o}\)ssbauer spectroscopy measurements carried out in polycrystalline YbIG, below TComp, show the clear signatures of field induced perpendicular Fe3+ spin configuration when applied external field is 50 kOe.
 
Article
In the last decades, the demand for steel has increased exponentially generating tons of waste impacting the environment. The most common waste in steelmaking process are slags which are produced during the rolling process of steel billets. This situation has encouraged the scientific community in finding environmentally possible ways to take advantage of this slags. In this work, we present the structural and magnetic properties of solid state recycled Q235 steel chips obtained by powder metallurgy and extrusion process from oxide scales of billets. The characterization of the recycled Q235 chips was performed by X-ray diffraction, Mössbauer spectroscopy and magnetic measurements. The X-ray diffraction reveals α-Fe as the predominant crystallographic phase and non-stoichiometric wüstite in minor amount. The Mössbauer spectrum revealed a sextet associated to α-Fe phase with a hyperfine magnetic field Bhf ~ 33 T and two doublets associated with Fe2+ and Fe3+ from the non-stoichiometric wüstite. Magnetic measurements show a ferromagnetic behavior because the presence of α-Fe which is the predominant phase and hysteresis is also observed under low applied fields.
 
Article
Inspired by the recent experimental evidences for double magicity in 52,54Ca, we have employed relativistic mean-field (RMF) approach with density-dependent meson-nucleon couplings using DD-ME2 parameter for a systematic study of nuclei with neutron numbers N = 32 and 34 with the help of ground state properties of even–even nuclei. Our extensive calculations include deformation, binding energies, 2p-separation energies, radii, etc. We compare our results with the available experimental data and another parameter of RMF. Our results of potential energy surface, two proton shell gap, isotopic shift, and normalized radius demonstrate signature of double magicity in N = 32 and 34 isotones, in particular for 46,48Si, 60,62Ni along with what found for 52,54Ca.
 
Article
Hyperfine interactions in the Bi1−xLaxFeO3 ferrites (where x = 0.0225, 0.075, 0.9) have been studied by means of ⁵⁷Fe Mössbauer spectroscopy and ¹⁴⁰Ce time differential perturbed angular γ–γ correlation methods. The information about the line shift δ, the lattice εlat and the magnetic εmag contributions to the quadrupole shift ε, isotropic His and anisotropic Han contributions to the hyperfine magnetic field Hhf on ⁵⁷Fe nuclei, anharmonicity parameter m, distribution of the hyperfine magnetic field p(Hhf), and supertransferred hyperfine magnetic fields on ¹⁴⁰Ce probe nuclei were obtained. In all studied compounds, the Fe ions are in a high-spin trivalent state. In the compounds with x = 0.0225 and 0.075 spatially modulated cycloidal magnetic structures exist. It was found that the sign of the effective constant of magnetic anisotropy Keff changes with the variation of x from 0.0225 to 0.075. The substitution of Bi by La increases the value of the hyperfine magnetic field on ⁵⁷Fe nuclei from 494 kOe in Bi0.9775La0.0225FeO3 to 520 kOe in Bi0.1La0.9FeO3, i.e. by 26 kOe, while the corresponding supertransferred hyperfine magnetic field on ¹⁴⁰Ce probe nuclei decreases.
 
Article
149Sm synchrotron-radiation-based Mössbauer spectroscopy was performed in Sm-based intermetallics having a cubic crystal structure, Sm3Tr4Ge13, SmB6, SmBe13, and SmTr2Al20 (Tr = transition metals). In spite of the difference of the local structure around the Sm sites, the observed Mössbauer spectra consist of a single line at 300 K. On the other hand, Sm LIII-edge X-ray absorption spectra consist of two components, suggesting Sm2+ and Sm3+ states. Difference of the number of the spectral components between the Mössbauer spectroscopy and X-ray absorption spectroscopy is caused by the difference of the time window in the scattering process of these measurements. Correlation between the isomer shifts in the Mössbauer spectroscopy and average Sm valence states estimated from the X-ray absorption spectroscopy exhibits a linear correlation.
 
Top-cited authors
Wolfgang Sturhahn
  • California Institute of Technology
B. Jonson
  • Chalmers University of Technology
Paolo Crivelli
  • ETH Zurich
Ferdinand Schmidt-Kaler
  • Johannes Gutenberg-Universität Mainz
Paul Indelicato
  • French National Centre for Scientific Research