On the Mössbauer spectrum of γ-Fe2O3

Pollard, R. J.

doi:10.1007/bf02400440

Cited by 26 publications

(36 citation statements)

References 8 publications

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“…For both samples, the FC curves flatten out at the lowest temperatures in a way typical for interacting particles. 10 This is in contrast to the strong increase of the signal with decreasing temperature seen in typical samples of noninteracting particles. 10 Thus the magnetization data give further evidence for the importance of magnetic interactions between the particles.…”

Section: Resultsmentioning

confidence: 80%

“…9 The lowtemperature spectra of the 260-ARG-AIR aerogel show the opposite asymmetry and are typical for pure maghemite. 10 Application of a magnetic field B a to the nanoparticles may block the superparamagnetic relaxation of the magnetic moments and provide us with a means to estimate the magnetic moment of the particles. 7,8 Above the blocking temperature the induced magnetic hyperfine field, B ind = ͉B obs − B a ͉, is related to the magnetic moment via B obs Х B 0 ͑1 − k B T / B a ͒ + B a .…”

Section: Resultsmentioning

confidence: 99%

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Magnetic and Mössbauer spectroscopy studies of nanocrystalline iron oxide aerogels

Carpenter

Long

Rolison

et al. 2006

Journal of Applied Physics

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A sol-gel synthesis was used to produce iron oxide aerogels. These nanocrystalline aerogels have a pore-solid structure similar to silica aerogels but are composed entirely of iron oxides. Mössbauer experiments and x-ray diffraction showed that the as-prepared aerogel is an amorphous or poorly crystalline iron oxide, which crystallized as a partially oxidized magnetite during heating in argon. After further heat treatment in air, the nanocrystallites are fully converted to maghemite. The particles are superparamagnetic at high temperatures, but the magnetic properties are strongly influenced by magnetic interactions between the particles at lower temperatures.

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Section: Resultsmentioning

confidence: 80%

Section: Resultsmentioning

confidence: 99%

Magnetic and Mössbauer spectroscopy studies of nanocrystalline iron oxide aerogels

Carpenter

Long

Rolison

et al. 2006

Journal of Applied Physics

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“…These values, which are somewhat sensitive to total Fe alloying concentrations and fittings (Supplementary Fig. 7), do not correspond to either Fe 2 O 3 64,65 or metallic Fe 66,67 . One species matches the Mössbauer parameters of high spin (HS) Fe 3+ in the oxide ligand field of NiFeO x 5,68,69 and FeOOH 70 .…”

Section: Resultsmentioning

confidence: 93%

Detection of high-valent iron species in alloyed oxidic cobaltates for catalysing the oxygen evolution reaction

Hadt

Hayes

et al. 2021

Nat Commun

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Iron alloying of oxidic cobaltate catalysts results in catalytic activity for oxygen evolution on par with Ni-Fe oxides in base but at much higher alloying compositions. Zero-field 57Fe Mössbauer spectroscopy and X-ray absorption spectroscopy (XAS) are able to clearly identify Fe4+ in mixed-metal Co-Fe oxides. The highest Fe4+ population is obtained in the 40–60% Fe alloying range, and XAS identifies the ion residing in an octahedral oxide ligand field. The oxygen evolution reaction (OER) activity, as reflected in Tafel analysis of CoFeOx films in 1 M KOH, tracks the absolute concentration of Fe4+. The results reported herein suggest an important role for the formation of the Fe4+ redox state in activating cobaltate OER catalysts at high iron loadings.

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“…At 4.2 K values as high as 0.48 mm/s for ~A and 0.62 for bB have been reported (Pollard, 1988;Pollard and Morrish, 1987;Collyer et al, 1988;Mehner et al, 1990;de Bakker et al, 1991;Nikumbh et aL, 1992). In an attempt to resolve this discrepancy, variable-temperature Mrssbauer spectra (MS) between 8 K and 475 K, and in addition at 4.2 K and 275 K with the absorber subjected to an external field of 60 kOe, were collected for a number of wellcrystallized maghemite and Al-maghemite samples.…”

Section: Introductionmentioning

confidence: 97%

The Center Shift in Mössbauer Spectra of Maghemite and Aluminum Maghemites

Costa

1994

Clays and clay miner.

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Abstract--Synthetic, relatively well-crystallized aluminum-substituted maghemite samples, y-(Aly. Fe~_y)203, with y = 0, 0.032, 0.058, 0.084, 0.106 and 0.151 have been studied by X-ray diffraction and zero-field Mrssbauer spectroscopy in the range 8 K to 475 K, and also with an external field of 60 kOe at 4.2 K and 275 K. It was found that there are two different converging models for fitting the zero-field spectra of the maghemites with a superposition of two Lorentzian-shaped sextets, both resulting in inconsistent values for the hyperfine fields (Hhf) and/or the center shifts (6) of the tetrahedral (A) and octahedral (B) ferric ions. From the applied-field measurements it is concluded that there is a constant difference of 0.12 _+ 0.01 mm/s between 6B and 6A, regardless of the A1 content.

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On the Mössbauer spectrum of γ-Fe2O3

Cited by 26 publications

References 8 publications

Magnetic and Mössbauer spectroscopy studies of nanocrystalline iron oxide aerogels

Magnetic and Mössbauer spectroscopy studies of nanocrystalline iron oxide aerogels

Detection of high-valent iron species in alloyed oxidic cobaltates for catalysing the oxygen evolution reaction

The Center Shift in Mössbauer Spectra of Maghemite and Aluminum Maghemites

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