A low-temperature phase diagram for ilmenite-rich compositions in the system Fe2O3-FeTiO3

Burton, Benjamin P.; Robinson, Peter; McEnroe, Suzanne A.; Fabian, Karl; Ballaran, Tiziana Boffa

doi:10.2138/am.2008.2690

Cited by 37 publications

(88 citation statements)

References 43 publications

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“…The x-ray diffraction analysis given in Ref. 7 shows that Ilm95 is a pure rhombohedral phase of ilmenite-hematite while Ilm70 is almost purely rhombohedral with a small impurity of an unidentified phase. Unpublished data of Ilm80 indicates a pure ilmenite-hematite sample.…”

Section: Methodsmentioning

confidence: 99%

“…Both ilmenite ͑FeTiO 3 ͒ and hematite ͑␣-Fe 2 O 3 ͒ are antiferromagnetic and insulating but intermediate compositions can be ferrimagnetic and semiconducting. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] The system is of significant interest as a source of natural remnant magnetism on the earth, the moon, and the planet Mars. [8][9][10][11] It is also considered promising for spintronics applications.…”

Section: Introductionmentioning

confidence: 99%

“…[8][9][10][11] Rapid cooling quenches metastable solid solutions. [1][2][3][4][5][6][7] Previous measurements have revealed the overall magnetic properties of the ilmenite-hematite system ͑for phase diagrams see Refs. 6 and 7͒ but at the atomic scale, the magnetic ordering remains largely unresolved.…”

Section: Introductionmentioning

confidence: 99%

“…6 and 7͒ but at the atomic scale, the magnetic ordering remains largely unresolved. 7,9,15 For 0.5 Շ x Ͻ 1.0 magnetization measurements show that solid solutions are significantly magnetic, up to more than ϳ30 A m 2 / kg for compositions of x ϳ 0.6-0.7, 1-3 due to Fe 3+ ͑or Fe 2+ ͒ ions substituting for Ti 4+ in the B layers, resulting in a ferrimagnetic structure. 2,4,17 Neutron diffraction has shown that for 0.5Շ x Ͻ 1.0 essentially all Ti 4+ is in the B layers but the cation distribution within layers is inhomogenous.…”

Section: Introductionmentioning

confidence: 99%

“…5 Magnetization measurements suggest that small magnetic clusters exist, with long-range magnetic correlations beyond a percolation threshold of x Յ 0.87. 7,17 However, the details of Fe 2+ / Fe 3+ charge-ordered cation distribution and their implications for magnetic ordering are yet to be clarified.…”

Section: Introductionmentioning

confidence: 99%

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Magnetic clusters in ilmenite-hematite solid solutions

Frandsen

Burton²,

Rasmussen

et al. 2010

Phys. Rev. B

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We report the use of high-field 57 Fe Mössbauer spectroscopy to resolve the magnetic ordering of ilmenitehematite ͓xFeTiO 3 − ͑1−x͒Fe 2 O 3 ͔ solid solutions with x Ͼ 0.5. We find that nanometer-sized hematite clusters exist within an ilmenite-like matrix. Although both phases are antiferromagnetically ordered, the hematite clusters show ferrimagnetic behavior due to superexchange coupling with Fe 2+ in ilmenite. For ilmenite-rich samples ͑x = 0.95͒, the clusters are isolated and superparamagnetic. For more hematite-rich samples with x = 0.80 and x = 0.70, the clusters interact to form a cluster glass.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Magnetic clusters in ilmenite-hematite solid solutions

Frandsen

Burton²,

Rasmussen

et al. 2010

Phys. Rev. B

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Curie temperatures of titanomagnetite in ignimbrites: Effects of emplacement temperatures, cooling rates, exsolution, and cation ordering

Jackson

Bowles

2014

Geochem Geophys Geosyst

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Pumices, ashes, and tuffs from Mt. St. Helens and from Novarupta contain two principal forms of titanomagnetite: homogeneous grains with Curie temperatures in the range 350-500 C and oxyexsolved grains with similar bulk composition, containing ilmenite lamellae and having Curie temperatures above 500 C. Thermomagnetic analyses and isothermal annealing experiments in combination with stratigraphic settings and thermal models show that emplacement temperatures and cooling history may have affected the relative proportions of homogeneous and exsolved grains and have clearly had a strong influence on the Curie temperature of the homogeneous phase. The exsolved grains are most common where emplacement temperatures exceeded 600 C, and in laboratory experiments, heating to over 600 C in air causes the homogeneous titanomagnetites to oxyexsolve rapidly. Where emplacement temperatures were lower, Curie temperatures of the homogeneous grains are systematically related to overburden thickness and cooling timescales, and thermomagnetic curves are generally irreversible, with lower Curie temperatures measured during cooling, but little or no change is observed in room temperature susceptibility. We interpret this irreversible behavior as reflecting variations in the degree of cation ordering in the titanomagnetites, although we cannot conclusively rule out an alternative interpretation involving fine-scale subsolvus unmixing. Shortrange ordering within the octahedral sites may play a key role in the observed phenomena. Changes in the Curie temperature have important implications for the acquisition, stabilization, and retention of natural remanence and may in some cases enable quantification of the emplacement temperatures or cooling rates of volcanic units containing homogeneous titanomagnetites.

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Importance of titanohematite in detrital remanent magnetizations of strata spanning the Cretaceous‐Paleogene boundary, Hell Creek region, Montana

Sprain

Feinberg

Renne

et al. 2016

Geochem Geophys Geosyst

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Intermediate composition titanohematite, Fe 2-y Ti y O 3 with 0.5 y 0.7, is seldom the focus of paleomagnetic study and is commonly believed to be rare in nature. While largely overlooked in magnetostratigraphic studies, intermediate titanohematite has been identified as the dominant ferrimagnetic mineral in an array of Late Mesozoic and early Cenozoic Laramide clastic deposits throughout the central United States. Intermediate titanohematite is ferrimagnetic and has similar magnetic properties to titanomagnetite, except its unique self-reversing property. Due to these similarities, and with detrital remanent magnetizations masking its self-reversing nature, intermediate titanohematite is often misidentified in sedimentary deposits. Past studies relied upon nonmagnetic techniques including X-ray diffraction and electron microprobe analysis. While these techniques can identify the presence of intermediate titanohematite, they fail to test whether the mineral is the primary recorder. To facilitate the identification of intermediate titanohematite in sedimentary deposits, we characterize this mineral using low-temperature magnetometry and high-temperature susceptibility experiments, and present a new identification technique based on titanohematite's self-reversing property, for sediments that span the Cretaceous-Paleogene boundary (Hell Creek region, Montana). Results from the self-reversal test indicate that the majority of remanence is held by minerals that become magnetized parallel to an applied field, but that intermediate, selfreversing titanohematite (y 5 0.53-0.63) is an important ancillary carrier of remanence. While earlier literature suggests that intermediate titanohematite is rare in nature, reanalysis using specialized rock magnetic techniques may reveal that it is more abundant in the rock record, particularly within depositional basins adjacent to calc-alkaline volcanics, than previously thought.

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A low-temperature phase diagram for ilmenite-rich compositions in the system Fe2O3-FeTiO3

Cited by 37 publications

References 43 publications

Magnetic clusters in ilmenite-hematite solid solutions

Magnetic clusters in ilmenite-hematite solid solutions

Curie temperatures of titanomagnetite in ignimbrites: Effects of emplacement temperatures, cooling rates, exsolution, and cation ordering

Importance of titanohematite in detrital remanent magnetizations of strata spanning the Cretaceous‐Paleogene boundary, Hell Creek region, Montana

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