Three-dimensional micromagnetic calculations for magnetite using FFT

Fabian, Karl; Kirchner, Andreas; Williams, Wyn; Heider, Franz; Leibl, T.; Huber, Alexander

doi:10.1111/j.1365-246x.1996.tb06354.x

Cited by 148 publications

(130 citation statements)

References 37 publications

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“…The effect of neglecting magnetoelastic energies is likely to reduce the average width of domains [Worm et al, 1991]. For the models discussed in the present paper, it is assumed that magnetoelastic effects are small, though are likely to become more significant for grains larger than -5 gm [Fabian et al, 1996].…”

Section: E D _ -In O • M(rl ) H !Amentioning

confidence: 99%

High‐resolution micromagnetic models of fine grains of magnetite

Williams¹,

Wright²

1998

J. Geophys. Res.

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Abstract. High resolution three dimensional models are presented of cubic grains of magnetite in the grain size range 0.03 gm to 4.0 gm, achieved using a resolution of up to 262,144 elements to represent a single grain. Previous models have been limited in the maximum grain size that could be investigated because of the lack of resolution and increase in complexity of domain structure with grain size. This paper confirms the simple flower and vortex states found previously, but the classical two-domain (with closure domains) Kittel structure is shown not to be a local energy minimum state for magnetite. The concept of a single-domain to two-domain transition is now seen as a gradual unwinding of a flower state, and pseudo-single domain grains are shown to be vortex and multiple-vortex states. For grains greater than about 2 gm in size the center of vortices act a nucleation centers for the formation of domain walls. At the largest grains size modeled (4.0 gm), the expected features of multidomain grains are seen, with well-defined domain walls, and body domains with their magnetization aligned along the easy magnetocrystalline anisotropy axis.

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Section: E D _ -In O • M(rl ) H !Amentioning

confidence: 99%

High‐resolution micromagnetic models of fine grains of magnetite

Williams¹,

Wright²

1998

J. Geophys. Res.

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“…The existence of the metastable SD (MSD) state provides a possible explanation for the grain dimensions of the anomalously large magnetosomes [19,25]. As initially uniformly-magnetized magnetosomes nucleate and grow in size from the SPM state to the stable SD state and beyond, it may be energetically favorable for the grains to retain a near uniform SD state (flower state) into the metastable SD range instead of reverting to a non-SD state because the additional activation energy needed for the transformation is not available.…”

Section: Magnetosomes and Micromagnetismmentioning

confidence: 99%

“…As initially uniformly-magnetized magnetosomes nucleate and grow in size from the SPM state to the stable SD state and beyond, it may be energetically favorable for the grains to retain a near uniform SD state (flower state) into the metastable SD range instead of reverting to a non-SD state because the additional activation energy needed for the transformation is not available. Magnetic interactions between magnetosomes along a chain may also help to stabilize the SD structure [25].…”

Section: Magnetosomes and Micromagnetismmentioning

confidence: 99%

Biological Permanent Magnets

Frankel

2003

Hyperfine Interactions

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“…In small magnetite grains (o1 mm) curved vortex or flower states can occur as the preferred LEM [56][57][58][59] . Even repeated cycles of heating and cooling to the same temperature systematically change the statistical domain state 60 .…”

Section: Article Nature Communications | Doi: 101038/ncomms5548mentioning

confidence: 99%

Magnetic force microscopy reveals meta-stable magnetic domain states that prevent reliable absolute palaeointensity experiments

et al. 2014

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Obtaining reliable estimates of the absolute palaeointensity of the Earth's magnetic field is notoriously difficult. The heating of samples in most methods induces magnetic alteration-a process that is still poorly understood, but prevents obtaining correct field values. Here we show induced changes in magnetic domain state directly by imaging the domain configurations of titanomagnetite particles in samples that systematically fail to produce truthful estimates. Magnetic force microscope images were taken before and after a heating step typically used in absolute palaeointensity experiments. For a critical temperature (250°C), we observe major changes: distinct, blocky domains before heating change into curvier, wavy domains thereafter. These structures appeared unstable over time: after 1-year of storage in a magnetic-field-free environment, the domain states evolved into a viscous remanent magnetization state. Our observations qualitatively explain reported underestimates from otherwise (technically) successful experiments and therefore have major implications for all palaeointensity methods involving heating.

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Three-dimensional micromagnetic calculations for magnetite using FFT

Cited by 148 publications

References 37 publications

High‐resolution micromagnetic models of fine grains of magnetite

High‐resolution micromagnetic models of fine grains of magnetite

Biological Permanent Magnets

Magnetic force microscopy reveals meta-stable magnetic domain states that prevent reliable absolute palaeointensity experiments

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