Physical interpretation of hysteresis loops: Micromagnetic modeling of fine particle magnetite

Tauxe, Lisa; Bertram, H.N.; Seberino, C.

doi:10.1029/2001gc000241

Cited by 183 publications

(214 citation statements)

References 47 publications

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“…This hypothesis is reinforced by the fact that the hystereis curves show well-defined wasp-waisted (C) behavior (Tauxe et al, 1996) probably due to presence of mixture single-domain and superparamagnetic grains (Goguitchaichvili and Prévot, 2000). Further evidence of SD-SP grains comes from the squareness vs. coercitive force (Hc) relationship (Tauxe et al, 2002) pointing to the uniaxial SD and SP mixture. Conventional microscopy observations are rather difficult because of small size of most magnetic grains (commonly less than 2 μm).…”

Section: Sample Selectionmentioning

confidence: 77%

Early cretaceous absolute geomagnetic paleointensities from Córdoba Province (Argentina)

et al. 2006

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We present here new paleointensity and geochronology results from Early Cretaceous volcanic rocks of Sierra Chica de Cordoba (Argentina). The new K-Ar isotopic ages of 5 samples range from 136 to 122 Ma. Twenty five samples from 7 individual flows yielded acceptable paleointensity estimates. The mean paleointensity values per flow are ranging from 53.0 ± 1.9 to 25.4 ± 2.6 μT and the corresponding Virtual Dipole Moments (VDMs) are ranging from 9.3±1.3 to 4.6±0.5 (10 22 Am 2 ). This corresponds to the mean value of 7.3±1.7×10 22 Am 2 , which is compatible to the present geomagnetic axial dipole. Currently available selected paleointensity data from 80 to 130 Ma suggest that geomagnetic field strength frequently fluctuated before and during the Cretaceous Normal Superchron while the magnetic polarity maintained stable. The mean paleointensities derived from Córdoba lavas agree remarkably well with those obtained from the Paraná Magmatic Province (133-132 Ma). This reinforces the hypothesis about the unreliability of 'Mesozoic Dipole Low'.

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Section: Sample Selectionmentioning

confidence: 77%

Early cretaceous absolute geomagnetic paleointensities from Córdoba Province (Argentina)

et al. 2006

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“…Saturation is reached in moderate fields of 200-400 mT, which points to spinels as remanence carriers. Following Tauxe et al (2002), we plot hysteresis parameters showing those that belong to the vortex remanent states' contribution to PSD hysteresis behavior, as suggested by Williams and Dunlop (1995) (Fig. 8(b)).…”

Section: Hysteresis Measurementsmentioning

confidence: 99%

Comprehensive paleomagnetic study of a succession of Holocene olivine-basalt flow: Xitle Volcano (Mexico) revisited

Alva‐Valdivia

2005

Earth Planet Sp

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A detailed paleomagnetic study of a young Late Holocene olivine-basalt flow from the Xitle volcano in the southern Basin of Mexico was completed to evaluate the consistency and reliability of the record derived from fresh well-preserved and exposed lava flows. One-hundred oriented standard paleomagnetic cores corresponding to 10 different lava effusion episodes were collected from unit-flow V. Thermomagnetic analyses show that bulk magnetic properties and remanence is carried in most cases by Ti-poor titanomagnetite, presumably resulting from oxy-exsolution processes during the initial flow cooling. Unblocking temperature and coercivity suggests pseudo-single domain magnetic grains for these (titano)magnetites. Thermal and alternating field demagnetizations show well-defined univectorial magnetizations. Most sites present a mean direction with small angular dispersion around the dipolar direction for central Mexico. The overall mean direction (N = 10, Dec = 1.1• , Inc = 34.1• , k = 531 and α 95 = 2.1 • ) is characterized by small angular dispersion and inclination close to the dipolar value for the locality. Anisotropy of magnetic susceptibility lineation agrees with the geologically-inferred flow direction. Various samples from the 10 lava flows were selected for Thellier paleointensity experiments because of their stable remanent magnetization and relatively low within-site dispersion. According to reliability parameters, the obtained paleointensities are of reasonably good quality. Nine mean paleointensities range between 48.6 and 73.9 μT. The overall mean paleointensity of 59.9-7.7 μT is higher than the present-day field of 43 μT, consistent with the global data for this time-period. Most samples presented alteration during the cooling rate test, and no correction was made to these samples. Those samples on which cooling-rate correction was applied give a flow mean lower than the raw paleointensity data, as was expected.

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“…Direct current magnetization and alternating field demagnetization curves can also determine whether magnetic particles interact (Cisowski 1981). M r /M S Â H C diagrams have become relevant in characterizing the magnetic domain of particles in animal tissues (Tauxe et al 2002).…”

Section: Appendix A: Characterization Techniquesmentioning

confidence: 99%

Magnetoreception in eusocial insects: an update

Wajnberg

Acosta‐Avalos

Alves

et al. 2010

J. R. Soc. Interface.

110

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Behavioural experiments for magnetoreception in eusocial insects in the last decade are reviewed. Ants and bees use the geomagnetic field to orient and navigate in areas around their nests and along migratory paths. Bees show sensitivity to small changes in magnetic fields in conditioning experiments and when exiting the hive. For the first time, the magnetic properties of the nanoparticles found in eusocial insects, obtained by magnetic techniques and electron microscopy, are reviewed. Different magnetic oxide nanoparticles, ranging from superparamagnetic to multi-domain particles, were observed in all body parts, but greater relative concentrations in the abdomens and antennae of honeybees and ants have focused attention on these segments. Theoretical models for how these specific magnetosensory apparatuses function have been proposed. Neuron-rich ant antennae may be the most amenable to discovering a magnetosensor that will greatly assist research into higher order processing of magnetic information. The ferromagnetic hypothesis is believed to apply to eusocial insects, but interest in a light-sensitive mechanism is growing. The diversity of compass mechanisms in animals suggests that multiple compasses may function in insect orientation and navigation. The search for magnetic compasses will continue even after a magnetosensor is discovered in eusocial insects.

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Physical interpretation of hysteresis loops: Micromagnetic modeling of fine particle magnetite

Cited by 183 publications

References 47 publications

Early cretaceous absolute geomagnetic paleointensities from Córdoba Province (Argentina)

Early cretaceous absolute geomagnetic paleointensities from Córdoba Province (Argentina)

Comprehensive paleomagnetic study of a succession of Holocene olivine-basalt flow: Xitle Volcano (Mexico) revisited

Magnetoreception in eusocial insects: an update

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