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  • 1
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Nuclear inelastic resonant scattering of synchrotron radiation was applied to the study solutions of 57Fe complexes. In order to reveal different inelastic contributions solutions of two different 57Fe complexes of different molecular dimensions with solvents of substantially different viscosities were studied. We argue that the only former experiment available in the literature overestimates the role of the diffusivity in affecting the spectrum. The first direct observation of an intramolecular vibrational transition assisting the nuclear resonance absorption in a liquid is reported.
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  • 2
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract 57Co Mössbauer emission spectra of undoped and Fe or Mg melt-doped LiNbO3 single crystals show substantial amounts of the nucleogenic Fe3+ charge state (*Fe3+) which was generated as an after-effect of the electron-capture of 57Co2+. The proportion of *Fe3+ is markedly dependent on the Mg content and on the stoichiometry of the sample. Electron trapping is described within the model of competing acceptors. The capabilities of the model are investigated in defect structure analysis and charge trapping studies of LiNbO3.
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  • 3
    ISSN: 1090-6487
    Keywords: 76.80.+y ; 75.50.Gg ; 75.60.Ej
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract 57Fe Mössbauer and magnetometric studies of the molecular ferrimagnet N(n-C5H11)4 [ FeIIFeIII(C2O4)3] are indicative of a 2D magnetic character with strong uniaxial anisotropy in the basal plane of the crystal. It is established that the change in the sign of the net magnetization of this compound is related to a compensation between FeIII and FeII sublattice magnetizations at T comp=31.2 K. The form and parameters of the magnetic Hamiltonian describing the temperature dependence of the FeIII sublattice and the net magnetizations are determined.
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  • 4
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Synchrotron Mössbauer reflectometry and CEMS results on a [57Fe(2.55 nm)/FeSi\break(1.57 nm)]10 multilayer (ML) on a Zerodur substrate are reported. CEMS spectra are satisfactorily fitted by α‐Fe and an interface layer of random α‐(Fe, Si) alloy of 20% of the 57Fe layer thickness on both sides of the individual Fe layers. Kerr loops show a fully compensated AF magnetic layer structure. Prompt X‐ray reflectivity curves show the structural ML Bragg peak and Kiessig oscillations corresponding to a bilayer period and total film thickness of 4.12 and 41.2 nm, respectively. Grazing incidence nuclear resonant Θ–2Θ scans and time spectra (E = 14.413 keV, λ = 0.0860 nm) were recorded in different external magnetic fields (0 〈 Bext 〈 0.95 T) perpendicular to the scattering plane. The time integral delayed nuclear Θ–2Θ scans reveal the magnetic ML period doubling. With increasing transversal external magnetic field, the antiferromagnetic ML Bragg peak disappears due to Fe layer magnetization canting, the extent of which is calculated from the fit of the time spectra and the Θ–2Θ scans using an optical approach. In a weak external field the Fe layer magnetization directions are neither parallel with nor perpendicular to the external field. We suggest that the interlayer coupling in [Fe/FeSi]10 varies with the distance from the substrate and the ML consists of two magnetically distinct regions, being of ferromagnetic character near substrate and antiferromagnetic closer to the surface.
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  • 5
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Temperature dependence of the magnetization measurements and Conversion Electron Mössbauer Spectroscopy (CEMS) have been performed on sputtered Bi3Fe5O12 (BiIG), Y3Fe5O12 (YIG) and (Bi, Y)IG films. Under the effect of the diamagnetic dilution of the diamagnetic yttrium sublattice the magnetization of BiIG is decreased with respect to YIG. The hyperfine field at the tetrahedral iron sites is increased, indicating a decrease in the intra-sublattice exchange interaction rather than the decrease of the tetrahedral iron moment.
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  • 6
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Mössbauer spectroscopy, X-ray diffractometry, ESR and electrical resistivity measurements, were used to study highT c (above 100 K) superconducting materials in order to get information about the effect of the preparation circumstances as well as about the anomalous behaviour in57Fe and119Sn doped TlBaCaCu(57Fe)O4.5+δ and TlBaCuCu(119Sn)O4.5+δ superconductors. We have found that the Mössbauer parameters strongly depend on the preparation circumstances. In many cases the presence of Mössbauer lines of nonsuperconducting oxide phases indicated that the iron and tin could not entirely built in into the lattice of superconductor. Four valence state tin and four valence state iron sites were identified in the superconducting phases. We have found anomalous temperature dependent changes in the57Fe Mössbauer spectra of TlBaCaCu(57Fe)O4.5+δ samples around theT c between 105–135 K. In this temperature range the total area of the spectrum temporary increases.
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  • 7
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report on calculations of the angle- and time-dependent photon reflectivity of multilayers using the technique of characteristic matrices. Spectra of56Fe/57Fe and Cr/Fe multilayers are calculated under various conditions. The parameters of the multilayers are optimized for suitable test samples of reflectometry measurements.
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  • 8
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract YBa2(Cu1-x 57Fe x )3O7−y powder samples withx=0.02 and 0.03 were uniaxiallyc-aligned in epoxy in a magnetic field of 7.5 T. An X-ray map of the distribution of the orientation of the crystallographicc-axes of the individual crystallites was determined.57Fe Mössbauer spectra were recorded at room temperature as a function of the angle between the texture axis and the observation direction. Different sets of EFG parameters were selected from the literature and the fit constraints were equally set for all. Using a model of the measured texture function and accounting for polarization-dependent blackness effects, a simultaneous fit of the Mössbauer spectra results in minimumϰ 2 for the EFG set determined previously from CEMS data on this films.
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  • 9
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Hydrogen desorption during heat treatments of (crystalline) Zr3FeH5.5 was studied by Mössbauer spectroscopy (MS), X-ray (powder) diffraction (XRD) and thermal gravimetry (TG). In case of sufficiently slow heating rate all hydrogen effuses below 650°K and no phase segregation occurs. At higher temperatures retained hydrogen induce phase separation into Fe2Zr (or more likely Fe2ZrHx) and zirconium hydride. The existence of a highly disordered f.c. tetragonal ternary hydride phase was also detected both by XRD (ao=4.76 Å, c=4.96 Å) and MS $$(\bar I\bar S = - 0.14,\bar \Delta \bar E = 0.34)$$ .
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Hyperfine interactions 125 (2000), S. 197-204 
    ISSN: 1572-9540
    Keywords: nuclear optics ; correlations ; energy domain ; time domain ; forward scattering ; grazing incidence ; inequivalent nuclear site ; cover layer ; substrate layer ; periodic multilayer ; simultaneous fit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The program EFFINO (Environment For FItting Nuclear Optics) evaluates Mössbauer absorption and time spectra both in nuclear forward scattering and in grazing incidence reflection geometry. Time‐integral prompt and delayed angular scan spectra are also treated. The time spectra are calculated by Fourier transformation from frequency to time domain. The electric quadrupole and magnetic dipole fields at the nuclear sites are considered static at present. The specimen in both forward scattering and grazing incidence is assumed to be a multilayer, with individual thickness and interface roughness (the latter only for the grazing incidence case at present) and electronic index of refraction. Up to eight different layers plus eight repetition periods of those layers are treated. Each layer may contain zero to eight nuclear sites (zero in all layers being prompt X‐ray reflectivity), with their own effective thickness or (for grazing incidence) their own complex nuclear index of refraction. From the forward scattering amplitude, a differential 4 × 4 propagation matrix is constructed for each layer. Several experimental spectra of the same or different type(s) can be fitted simultaneously. Correlations between parameters of the same or of different spectra can be introduced.
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