Mössbauer Paramagnetic Hyperfine Structure

Wickman, H. H.

doi:10.1007/978-1-4757-1544-6_3

Cited by 79 publications

(31 citation statements)

References 30 publications

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“…1) is in qualitative agreement with what is predicted by the conventional relaxation model: as the temperature is increased, the spectral lines should first broaden gradually and then collapse into a single line or a quadrupole doublet, the relaxation rate growing [16,24]. At the same time the conventional model essentially implies that the broadening should be Lorentzian over the whole temperature range; accordingly, the spectrum should develop fairly long wings, detectable by careful evaluation of the spectrum.…”

Section: Mössbauer Spectra In the Gtlr Modelsupporting

confidence: 75%

“…This separation should result in a difference between the respective rates at which the two transitions occur, p 12 ( ∆ E ) and p 21 ( ∆ E ) . The GTLR model yields a variety of shapes for absorption Möss-bauer spectra in a time-dependent magnetic field [16,24]. It should enable one to qualitatively explain all the peculiarities observed.…”

Section: Mössbauer Spectra In the Gtlr Modelmentioning

confidence: 95%

“…In the case of zero interaction (∆E = 0, = p, ∆p = 0), we arrive at a well-known formula of the conventional two-level relaxation model [16].…”

Section: Mössbauer Spectra In the Gtlr Modelmentioning

confidence: 99%

“…Consequently, superparamagnetic relaxation can have a dominant influence on the shape of Mössbauer spectra. To a first approximation, this effect can be described by the two-level relaxation model in which the magnetic moment of an individual particle is always parallel to the easiest magnetic axis of the particle but changes orientation randomly with time [16]. In its conventional form, the model was indeed employed by many workers for Mössbauer-spectrum evaluation [17][18][19][20][21][22][23].…”

Section: Mössbauer Spectra In the Gtlr Modelmentioning

confidence: 99%

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Mossbauer-Spectroscopy Characterization of Nanostructured Magnetic Materials

Aksenova

Чуев

2005

Russ Microelectron

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Two mechanisms are examined underlying the formation of the magnetic hyperfine structure in the Mössbauer spectra of magnetic materials containing nanoparticles. The absorption spectra of 57 Fe nuclei in FeCu-Nb-B nanostructured magnetic alloys are evaluated within the generalized two-level relaxation model, which includes interparticle interaction. All the unconventional features of the spectra are thus explained in qualitative terms. Furthermore, the precession of the magnetic moments of nanoparticles in a magnetic anisotropy field is investigated. It is shown that in a precessing hyperfine field the nuclear g factors should be subject to renormalization. As a result, the hyperfine spectra should undergo a radical transformation. It is concluded that the conventional techniques of Mössbauer-spectra evaluation in the context of nanostructured magnetic materials should be modified to include the transformation. NANOSTRUCTURE CHARACTERIZATION

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Section: Mössbauer Spectra In the Gtlr Modelsupporting

confidence: 75%

Section: Mössbauer Spectra In the Gtlr Modelmentioning

confidence: 95%

“…In the case of zero interaction (∆E = 0, = p, ∆p = 0), we arrive at a well-known formula of the conventional two-level relaxation model [16].…”

Section: Mössbauer Spectra In the Gtlr Modelmentioning

confidence: 99%

Section: Mössbauer Spectra In the Gtlr Modelmentioning

confidence: 99%

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Mossbauer-Spectroscopy Characterization of Nanostructured Magnetic Materials

Aksenova

Чуев

2005

Russ Microelectron

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“…The value of ~ 55 T for Bhlis typical of that expected for the + 5/2 Kramer's doublet from paramagnetic Fe(III) bound in an oxygen environment (Table 4) and undergoing slow relaxation. Structure from the + 3/2 and _+ 1/2 Kramer's doublets would be expected to occur with Bhl = ~33 T and 11 T, respectively (Wickman, 1966), which might be difficult to see because of overlap with other components in the spectra. Also Fysh et al (1983), reporting on kaolinite in which they observed similar structure, presented arguments for more rapid relaxation of the + 3/2 and _+ 1/2 Kramer's doublets than for the + 5/2 state.…”

Section: Resultsmentioning

confidence: 99%

Evidence for the multiphase nature of bentonites from Mössbauer and EPR spectroscopy

Goodman¹,

Nadeau²,

Chadwick³

1988

Clay miner.

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: M/Sssbauer spectra of several smectites demonstrate the existence of at least three phases with distinct Fe populations: (i) a component with very low Fe content (< 1~), which shows slowly-relaxing paramagnetic hyperfine structure at both 4.2 K and 77 K; (ii) a component with intermediate Fe content (~ 1-10H) which is seen as doublets in the spectra at 4.2 K, 77 K and ambient temperature; (iii) an Fe-rich phase (> 30~ Fe), which shows magnetic ordering at 4.2 K and 77 K. These data are consistent with components (i) and (ii) corresponding to Fe incorporated in aluminosilicate structures from distinct phases, whereas (iii) is characteristic of an iron oxide phase, probably goethite in most cases. These conclusions are supported by EPR measurements which show magnetically-dilute Fe in more than one type of structural environment plus an additional component with magnetically-interacting ions.

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The Temperature Dependent Line Shape of Mössbauer Hyperfine Spectra in the Paramagnetic and the Ordered Region

Schwegler

1972

Fortschr. Phys.

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A general, microscopic and quantum mechanical theory of the temperature dependent line shape of Mossbauer hyperfine spectra is presented. This theory covers the slow as well as the fast relaxation region and spectra of both paramagnetic and magnetically ordered samples. On a phenomenological level the theory results in generalized Wickman equations but with explicit expressions for the relaxation parameters in terms of the interaction Hamiltonians. The connection between this fully quantum mechanical theory and the stochastic models is also discussed. I n the second part relaxation times are calculated for special interaction Hamiltonians. The relation between the relaxation times obtained by Mossbauer measurements and the results of other relaxation time measurements, especially those of the longitudinal susceptibility XII, is also considered. In the third part the critical slowing down of the relaxation time above a transition point is briefly discussed. Finally the superparamagnetism hypothesis, which is able to explain the so-called anomalous spectra measured below transition points, is outlined.

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Mössbauer Paramagnetic Hyperfine Structure

Cited by 79 publications

References 30 publications

Mossbauer-Spectroscopy Characterization of Nanostructured Magnetic Materials

Mossbauer-Spectroscopy Characterization of Nanostructured Magnetic Materials

Evidence for the multiphase nature of bentonites from Mössbauer and EPR spectroscopy

The Temperature Dependent Line Shape of Mössbauer Hyperfine Spectra in the Paramagnetic and the Ordered Region

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