A comparison of the magnetic properties of synthetic titanomagnetites and basalts

Radhakrishnamurty, C.; Likhite, S.D.; Deutsch, E. R.; Murthy, G. S.

doi:10.1016/0031-9201(81)90095-9

Cited by 34 publications

(10 citation statements)

References 22 publications

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“…On the other hand, some materials are encountered relatively routinely in rock magnetism for which the domain state concept is challenging. For example, spin‐glass behavior is observed in titanomagnetites and titanohematites, where magnetic spins of constituent atoms are not aligned in a regular pattern (e.g., Ishikawa et al, ; Radhakrishnamurty et al, ), due to frustration of magnetic exchange interactions. Magnetic domains can be difficult to define across interface boundaries in crystals that contain lamellae or for skeletal crystal forms with irregular shapes (e.g., Harrison et al, ; Robinson et al, ; Williams et al, ).…”

Section: Is Magnetic Domain State Identification a Chimera?mentioning

confidence: 99%

Domain State Diagnosis in Rock Magnetism: Evaluation of Potential Alternatives to the Day Diagram

Roberts

Harrison

et al. 2019

JGR Solid Earth

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The Day diagram is used extensively in rock magnetism for domain state diagnosis. It has been shown recently to be fundamentally ambiguous for 10 sets of reasons. This ambiguity highlights the urgency for adopting suitable alternative approaches to identify the domain state of magnetic mineral components in rock magnetic studies. We evaluate 10 potential alternative approaches here and conclude that four have value for identifying data trends, but, like the Day diagram, they are affected by use of bulk parameters that compromise domain state diagnosis in complex samples. Three approaches based on remanence curve and hysteresis loop unmixing, when supervised by independent data to avoid nonuniqueness of solutions, provide valuable component‐specific information that can be linked by inference to domain state. Three further approaches based on first‐order reversal curve diagrams provide direct domain state diagnosis with varying effectiveness. Environmentally important high‐coercivity hematite and goethite are represented with variable effectiveness in the evaluated candidate approaches. These minerals occur predominantly in noninteracting single‐domain particle assemblages in paleomagnetic contexts, so domain state diagnosis is more critical for ferrimagnetic minerals. Treating the high‐coercivity component separately following normal rock magnetic procedures allows focus on the more vexing problem of diagnosing domain state in ferrimagnetic mineral assemblages. We suggest a move away from nondiagnostic methods based on bulk parameters and adoption of approaches that provide unambiguous component‐specific domain state identification, among which various first‐order reversal curve‐based approaches provide diagnostic information.

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Section: Is Magnetic Domain State Identification a Chimera?mentioning

confidence: 99%

Domain State Diagnosis in Rock Magnetism: Evaluation of Potential Alternatives to the Day Diagram

Roberts

Harrison

et al. 2019

JGR Solid Earth

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“…The Hopkinson peak in the plagioclase κ( T ) curve with a sharp descent just below 580°C (Figure 1a) is characteristic of SD magnetite [ Dunlop , 1974; Radhakrishnamurty et al , 1981; Clark and Schmidt , 1982]. A possible second peak with a descent around 675°C, the Curie point of hematite, is not seen in the cooling curve and is probably noise.…”

Section: Magnetic Properties Characterizationmentioning

confidence: 99%

“…A possible second peak with a descent around 675°C, the Curie point of hematite, is not seen in the cooling curve and is probably noise. In the heating curve of the dark minerals, κ is independent of T (Figure 1b), a hallmark of large MD grains where κ is governed by self‐demagnetization [ Dunlop , 1974; Deutsch et al , 1981; Radhakrishnamurty et al , 1981; Clark and Schmidt , 1982; Soffel et al , 1982]. The only magnetic mineral is magnetite.…”

Section: Magnetic Properties Characterizationmentioning

confidence: 99%

Linear and nonlinear Thellier paleointensity behavior of natural minerals

2005

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We tested single‐domain (SD) and multidomain (MD) theories of the acquisition and thermal demagnetization of thermoremanent magnetization (TRM) and partial TRM (pTRM) in Thellier paleointensity determination, using as samples plagioclase and mafic minerals extracted from Matachewan diabase dikes. Susceptibility, hysteresis, and coercivity data indicate that the plagioclase contains mainly SD grains of magnetite while the mafic minerals (clinopyroxene, biotite, and actinolite) contain mainly MD magnetite. The extracted minerals were used in simulated Thellier experiments with laboratory TRM as a proxy for natural remanent magnetization (NRM). The plagioclase behaved ideally, as predicted by Néel SD theory, giving a linear NRM‐pTRM (Arai) plot with positive pTRM checks. The mafic minerals behaved nonideally, with strongly curved Arai plots sagging below the ideal SD line, in accord with observations for MD magnetites and with predictions that in heating to moderate temperatures T, more TRM is lost than can be regained as pTRM, causing convex‐down Arai plots. In experiments with pTRM parallel to NRM, all pTRM tail checks were zero, but pTRM checks increasingly deviated from the Arai curve toward the SD line as T increased. However, in repeat Thellier experiments, pTRMs at all T agreed with the original pTRMs. The negative pTRM checks were therefore not due to physicochemical alteration but rather to departure from initial states with different magnetic histories than those of the original pTRMs. The inability of pTRM checks to reliably distinguish between MD behavior and irreversible alteration could lead to overestimates of paleointensity from straight‐line fits to the low‐T “unaltered” part of the Arai curve or underestimates from fits to high‐T data. Alternating field cleaning to 15 mT before each Thellier step made the Arai plot only marginally less curved. Low‐temperature demagnetization (LTD, zero‐field cycling through the 120 K Verwey transition) hardly changed the curvature of the Arai plot for pTRM parallel to NRM. For pTRM perpendicular to NRM, LTD led to an inflected Arai curve straddling the ideal SD line. Data of either form would not give reliable paleointensity values. No presently available pretreatment renders the paleointensity data of MD grains usable. SD and nearly SD grains which behave ideally in the Thellier experiment remain the only useful recorders of absolute paleointensity.

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“…Stoichiometric magnetite exhibits abrupt changes in magnetic properties near 120 K [Ozdemir et al, 1993; Radhakrishnamurty et al, 1981;Hodych, 1986]. Associated with these magnetic changes is the change in crystal structure from cubic to monoclinic (upon cooling of the sample), as well as the isotropic point (i.e., the temperature near 130 K where the first magnetocrystalline anisotropy constant K 1 becomes zero).…”

Section: Verwey Transition and Stoichiometric Magnetitementioning

confidence: 99%

Low‐temperature magnetic properties of magnetite

King

Williams²

2000

J. Geophys. Res.

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Abstract. Although several studies have recommended removal of secondary components of magnetic remanence by zero-field cycling from room temperature to a temperature much lower than the low temperature transition for magnetite (about 120 K), the method has not become a standard routine technique. This is partly due to the poor understanding of the behavior of magnetite particles at the low-temperature transition zone. Previous experiments by other researchers have used magnetite powders. In such powders it is always possible to attribute any discrepancy between the results observed and theory to possible existence of magnetostatic interaction effects or existence of elongated particles in samples presumed to

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A comparison of the magnetic properties of synthetic titanomagnetites and basalts

Cited by 34 publications

References 22 publications

Domain State Diagnosis in Rock Magnetism: Evaluation of Potential Alternatives to the Day Diagram

Domain State Diagnosis in Rock Magnetism: Evaluation of Potential Alternatives to the Day Diagram

Linear and nonlinear Thellier paleointensity behavior of natural minerals

Low‐temperature magnetic properties of magnetite

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