Mössbauer studies of the morin transition in bulk and microcrystalline α-Fe2O3†

Nininger, Robert C.; Schroeer, Dietrich

doi:10.1016/0022-3697(78)90213-5

Cited by 136 publications

(54 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The other two components can be attributed to hematite which has, and hematite which has not passed through a Morin transition; at 4.2~ ( Figure 7) these latter components have approximately equal areas. According to Nininger and Schroeer (1978), this would indicate that about half of the hematite particles have sizes below 200 ~, i.e., a median particle size of about 200 ~. This value is in good agreement with the mean crystal dimension parallel to the c-axis of 220 ---40 ,~ calculated from the widths at half height of six XRD lines with l ~ 0.…”

Section: Crystal Morphology and Size Of Goethite And Hematitesupporting

confidence: 76%

Effect of pH on the Formation of Goethite and Hematite from Ferrihydrite

Schwertmann¹,

Murad

1983

Clays and clay miner.

637

423

View full text Add to dashboard Cite

Abstraet~Storage of ferrihydrite in aqueous suspensions at 24~ and pHs between 2.5 and 12 for as long as three years resulted in the formation of goethite and hematite. The proportions and crystallinity of these products varied widely with the pH. Maximum hematite was formed between pH 7 and 8, and maximum goethite at pH 4 and at pH 12. The crystallinity of both products, as indicated by X-ray powder diffraction line broadening and magnetic hyperfine field values and distribution widths, was poorer, the lower the proportion of the corresponding product in the mixture. The existence of two competitive formation processes is suggested: goethite is formed via solution, preferably from monovalent Fe(III) ions [Fe(OH)z § and Fe(OH)4-], and hematite by internal rearrangement and dehydration within the ferrihydrite aggregates. This concept relates the proportions of goethite and hematite to the activity of the Fe(III) ion species in solution, and implies that conditions favorable for the formation of goethite are unfavorable for that of hematite and vice versa.

show abstract

Section: Crystal Morphology and Size Of Goethite And Hematitesupporting

confidence: 76%

Effect of pH on the Formation of Goethite and Hematite from Ferrihydrite

Schwertmann¹,

Murad

1983

Clays and clay miner.

637

423

View full text Add to dashboard Cite

show abstract

“…[262][263][264][265][266][267][268]. Theoretical work showed that the Morin transition depends on a via adependent dipolar anisotropy term [260], and the size effect of T M 0 (D) has been induced by the change of the dipolar magnetic field with a lattice expansion [263,269,270]. This is in partial agreement with observed pressure dependencies of T M 0 [271,272].…”

Section: The Morin Transitionsupporting

confidence: 79%

Size Dependence of Structures and Properties of Magnetic Materials

Jiang¹,

Lang²

2007

TONANOJ

View full text Add to dashboard Cite

Due to the involvement of high portion of atomic coordination imperfection in surfaces and interfaces, the properties of magnetic nanocrystals dramatically differ from that of the corresponding bulk counterparts, which have led to a surge in both experimental and theoretical investigations in the past decades. This review summarizes the studies for these size-dependent magnetic properties, and additional thermal or phase stabilities, and mechanical properties. To interpret the above phenomena, a thermodynamic model for the size dependence and interface dependences of these properties is described, which is based on Lindemann s criterion for melting, Mott s expression for the vibrational melting entropy, and Shi s model for the size-dependent melting temperature. The model without any adjustable parameter is confirmed by a large number of experimental results, and helps us to understand the structures and properties of the magnetic nanocrystals. Moreover, other theoretical works on the above properties are also mentioned and commented.

show abstract

“…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: Resultsmentioning

confidence: 99%

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

Mössbauer studies of the morin transition in bulk and microcrystalline α-Fe2O3†

Cited by 136 publications

References 36 publications

Effect of pH on the Formation of Goethite and Hematite from Ferrihydrite

Effect of pH on the Formation of Goethite and Hematite from Ferrihydrite

Size Dependence of Structures and Properties of Magnetic Materials

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

Contact Info

Product

Resources

About