Nature of the morin transition in al-substituted hematite

Grave, E. De; Chambaere, D.; Bowen, L. H.

doi:10.1016/0304-8853(83)90074-4

Cited by 59 publications

(15 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For the St. Leon le Grand sample two magnetic components were noted (Figure 3) whose parameters (Table 1) agree with literature values for magnetite (Papamarinopoulos et al, 1982). Both the South Nation River landslide and Grande Baleine samples gave magnetic field values, H, at RT indicating hematite with little or no substitution (DeGrave et al, 1982(DeGrave et al, , 1983; however, A remained at -0.2 mm/s for the South Nation River landslide sample at 15 K and A = 0.0 mm/s for the Grande Baleine sample at 12 K. These values indicate a particle size on the order of 200 A for the latter and even less for the South Nation River landslide sample. Larger particles of hematite should have A ~ +0.4 mm/s at low temperature (Nininger and Schroeer, 1978 …”

Section: Resultssupporting

confidence: 84%

Mössbauer Spectroscopic Study of the Iron Mineralogy of Post-Glacial Marine Clays

Torrance

1986

Clays and clay miner.

View full text Add to dashboard Cite

Abstract--Three post-glacial marine clays from eastern Canada and one marine clay from Japan have been studied by M6ssbauer spectroscopy to ascertain their iron mineralogy. Small amounts of hematite (in two samples) and magnetite (in one sample) were found in the Canadian clays, and hematite was detected in the Japanese clay. The major spectral components were ferrous and ferric doublets, consistent with X-ray powder diffraction results that show chlorite, mica, and amphibole in the Canadian samples and smectite in the Japanese sample. Citrate-dithionite extraction removed hematite and most of the magnetite from these samples. Acid-base extraction also removed chlorite and some mica from the Canadian samples. Samples treated by these extractions had appreciably lower geotechnical yield stresses at given water contents.

show abstract

Section: Resultssupporting

confidence: 84%

Mössbauer Spectroscopic Study of the Iron Mineralogy of Post-Glacial Marine Clays

Torrance

1986

Clays and clay miner.

View full text Add to dashboard Cite

show abstract

“…One of these aspects concerns the relation between T M and the hematite particle size: smaller particle sizes (or, more generally speaking, poorer crystallinities) lead to decreased values for T M , and to an increased temperature range DT M = T f j T i over which the MT evolves. In this transition region, the TMS consist of a superposition of two sextet components, one arising from Fe 3+ species that belong to domains that exhibit AF ordering, and a second one arising from Fe 3+ species that belong to domains that exhibit WF ordering [23]. The two sextets are characterized by distinctive values for their hyperfine field and quadrupole shift.…”

Section: Surface Morin Transition In Hematites A-fe 2 Omentioning

confidence: 98%

ILEEMS: Methodology and Applications to Iron Oxides

2005

Self Cite

View full text Add to dashboard Cite

ILEEMS is the acronym for Integral Low-energy Electron Mössbauer Spectroscopy. In this variant of Mössbauer spectroscopy the low-energy electrons, E < õ15 eV, emitted by the probe nuclei in the absorber are counted as a function of source velocity. As a consequence of their low energy, the detected electrons' origin lies within a very thin surface layer with thickness of a few nanometers and consequently, ILEEMS is a useful technique to examine surfaces of Fecontaining substances. In a first part of this paper the authors briefly describe the design of a homemade ILEEMS equipment allowing the temperature of the investigated sample to be varied between 77 K and room temperature. The second part of this contribution deals with a selection of results obtained from ILEEMS spectra for various Fe oxides. In particular, the following items are covered: (1) surface versus bulk Morin transition in small-particle and near-bulk hematite, aFe 2 O 3 ; (2) bulk and thin-film magnetite, Fe 3 O 4 ; (3) ferrihydrite, 5Fe 2 O 3 I 9H 2 0, goethite, a-FeOOH, and lepidocrocite, g-FeOOH, all to some extent in relation to their morphology. Interesting and intriguing findings concerning the surface properties of these oxides were obtained and it is argued that the results encourage more systematic research in this and related fields using the surfacesensitive ILEEMS technique.

show abstract

“…Below T M the magnetic moments are antiparallel along the c-axis and the compound is a pure antiferromagnet (AF). The transition is suitably studied by Mössbauer spectroscopy because of the significant change in the quadrupole shift (2() from ; j0.20 mm/s for WF to ; +0.38 mm/s for AF [1][2][3]. T M can be modified or suppressed by different causes.…”

Section: Introductionmentioning

confidence: 99%

Study of the Morin Transition in Pseudocubic α-Fe2O3 Particles

et al. 2005

View full text Add to dashboard Cite

We have studied the Morin transition in nanostructured pseudocubic a-Fe 2 O 3 particles of about 1.8 mm side. The preparation was carefully chosen to obtain a system with a very narrow crystallite size distribution and particles of homogeneous morphology. Two samples were studied: one without thermal treatment (a-Fe 2 O 3 (ap)) and another annealed at 673 K in air for 12 h (aFe 2 O 3 (an)). Both were characterized by XRD, SEM, TGA and Mössbauer spectroscopy. The results indicate that the Morin transition is suppressed for a-Fe 2 O 3 (ap), however, a-Fe 2 O 3 (an) has a T M $ 230 K and the transition is completed over a very narrow temperature range. These results are discussed in connection with the crystallite size, the cell parameters, and the presence of OH j groups (hydrohematite) or incorporated water (protohematite).

show abstract

Nature of the morin transition in al-substituted hematite

Cited by 59 publications

References 6 publications

Mössbauer Spectroscopic Study of the Iron Mineralogy of Post-Glacial Marine Clays

Mössbauer Spectroscopic Study of the Iron Mineralogy of Post-Glacial Marine Clays

ILEEMS: Methodology and Applications to Iron Oxides

Study of the Morin Transition in Pseudocubic α-Fe2O3 Particles

Contact Info

Product

Resources

About