Magnetization of Ilmenite-Hematite System at Low Temperatures

Bozorth, R. M.; Walsh, Dorothy E.; Williams, A. J.

doi:10.1103/physrev.108.157.2

Cited by 40 publications

(15 citation statements)

References 8 publications

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“…Exsolved titanomagnetite grains with hemoilmenite lamellae are abundant in most of our samples. The magnetic properties of hemoilmenites have been investigated previously using the synthetic samples (Bozorth et al, 1957;Ishikawa and Akimoto, 1957;Ishikawa, 1962). Samples in the composition range x ≤ 0.21 in the formula xFe 2 O 3 ·(1− x)FeTiO 3 show peaks in the high-field (2 T) magnetization curves which shift towards lower temperatures with increasing hematite content.…”

Section: Discussionmentioning

confidence: 99%

Magnetic properties of subaerial basalts at low temperatures

Kosterov

2014

Earth Planet Sp

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Magnetic properties have been measured as a function of temperature from 2 K to room temperature for twentyone samples of subaerial basalts of different origin and age, using an MPMS instrument. In all samples but four, titanomagnetite with a titanium content of less than 5 per cent has been determined as a dominant magnetic mineral carrying NRM from χ(T ) measurements above room temperature and Verwey transition observations. However, the new low-temperature experiments yielded evidence of the presence of another magnetic mineral in all samples. This mineral accounts for up to 70 per cent of saturation magnetization at 2 K and acquires a relatively strong but thermally unstable SIRM at this temperature. Comparison of susceptibility vs. temperature curves measured in low and high DC biasing fields reveals evidence of superparamagnetic behavior, peaks marking the effective blocking temperatures being shifted from <2 K to about 16 K by a 4.8 T DC magnetic field. At the same time, the presence of peaks in the high-field susceptibility curves indicate that the corresponding magnetic phase does not reach saturation, even in the highest field available to us. A possible candidate to account for these properties is a hemoilmenite with 8-10 mole per cent of hematite, originating from high-temperature deuteric oxidation. This is in accordance with the prevailing occurrence of exsolution lamellae within titanomagnetite grains observed in scanning electron microscopy (SEM) images.

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Section: Discussionmentioning

confidence: 99%

Magnetic properties of subaerial basalts at low temperatures

Kosterov

2014

Earth Planet Sp

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“…when the stoechiometry between these A and B ions is 111. The first magnetic studies concerning Prussian blue-like phases were performed by Bozorth and coworkers three decades ago, who reported on magnetic ordering temperatures as high as 50 K [49]. Unfortunately, these authors did not characterize properly their compounds.…”

Section: Prussian Blue-like Phasesmentioning

confidence: 98%

Bimetallic Molecular-Based Magnetic Materials

Kahn

1996

Molecular Magnetism: From Molecular Assemblies to the Devices

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Among all the molecules and molecular assemblies relevant to molecular magnetism [1], those containing two (or possibly more) kinds of metal ions have played a particularly important role. Two reasons, at least, justify this situation. First, the diversity of the situations which can be encountered concerning the interaction between two spin carriers A and B within a molecular unit is much greater when A and B are different. For instance, the strict orthogonality of the magnetic orbitals leading to the stabilization of the molecular state of highest spin multiplicity is much easier to achieve in heterobimetallic than in homobimetallic species [2]. Secondly, with several kinds of magnetic centers, it is possible to design molecular lattices showing quite peculiar spin topologies. It is in particular the case of ferrimagnetic lattices.The first review article devoted to the magnetism of heteropolymetallic systems appeared in 1987 [3]. Since, this field has developed tremendously, in particular in relation with the synthesis of molecular-based magnets. This short review will be organized around the central theme of bimetallic magnets. The next section reviews some key concepts in molecular magnetism, such as spin delocalization and polarization, and then treats of the interaction between two spin carriers. Each subsequent section, from III to VII, is devoted to one type of bridge which have already allowed to design molecular-based magnets. To date, these bridges are : oxamato, oxamido, oxalato, dithiooxalato, oximato,

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“…However, the Verwey transition is highly sensitive to nonstoichiometry, cation substitution and grain size effects and is thus often obscured or missing in natural bulk material. Potential contributions could also originate from titanomagnetites (Fe 3–x Ti x O 4 ; 0 ≤ x ≤ 1) with high titanium contents (x ≳ 0.75) which have Curie temperatures below 300 K and high magnetic stabilities at low temperature [ Schmidbauer and Readman , 1982] or titanohematites (Fe 2–y Ti y O 3 ; 0 ≤ y ≤ 1) with similar magnetic properties for high‐Ti (y ≳ 0.75) compounds [ Bozorth et al , 1957; Ishikawa et al , 1985]. …”

Section: Thermomagnetic Analysesmentioning

confidence: 99%

Rock magnetic signatures in diagenetically altered sediments from the Niger deep‐sea fan

Dillon

Bleil

2006

J. Geophys. Res.

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[1] Diagenesis has extensively affected the magnetic mineral inventory of organic-rich late Quaternary sediments in the Niger deep-sea fan. Changes in concentration, grain size, and coercivity document modifications of the primary magnetic mineral assemblages at two horizons. The first front, the modern iron redox boundary, is characterized by a drastic decline in magnetic mineral content, coarsening of the grain size spectrum, and reduction in coercivity. Beneath a second front, the transition from the suboxic to the sulfidic anoxic domain, a further but less pronounced decrease in concentration and bulk grain size occurs. Finer grains and higher coercive magnetic constituents substantially increase in the anoxic environment. Low-and high-temperature experiments were performed on bulk sediments and on extracts which have also been examined by X-ray diffraction. Thermomagnetic analyses proved ferrimagnetic titanomagnetites of terrigenous provenance as the principal primary magnetic mineral components. Their broad range of titanium contents reflects the volcanogenic traits of the Niger River drainage areas. Diagenetic alteration is not only a grain size selective process but also critically depends on titanomagnetite composition. Low-titanium compounds are less resistant to diagenetic dissolution. Intermediate titanium content titanomagnetite thus persists as the predominant magnetic mineral fraction in the sulfidic anoxic sediments. At the Fe redox boundary, precipitation of authigenic, possibly bacterial, magnetite is documented. The presence of hydrogen sulfide in the pore water suggests a formation of secondary magnetic iron sulfides in the anoxic domain. Grain size-specific data argue for a gradual development of a superparamagnetic and single-domain iron sulfide phase in this milieu, most likely greigite.Citation: Dillon, M., and U. Bleil (2006), Rock magnetic signatures in diagenetically altered sediments from the Niger deep-sea fan,

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Magnetization of Ilmenite-Hematite System at Low Temperatures

Cited by 40 publications

References 8 publications

Magnetic properties of subaerial basalts at low temperatures

Magnetic properties of subaerial basalts at low temperatures

Bimetallic Molecular-Based Magnetic Materials

Rock magnetic signatures in diagenetically altered sediments from the Niger deep‐sea fan

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