Magnetic vortex effects on first-order reversal curve (FORC) diagrams for greigite dispersions

Valdez-Grijalva, Miguel A.; Muxworthy, Adrian R.; Williams, Wyn; Conbhuí, Pádraig Ó; Nagy, Lesleis; Roberts, Andrew P.; Heslop, David

doi:10.1016/j.epsl.2018.08.027

Cited by 26 publications

(38 citation statements)

References 37 publications

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“…This combination of negative and positive peaks has been reported previously for vortex systems (Pike and Fernandez, 1999;Carvallo et al, 2003;Valdez-Grijalva et al, 2018a). FORC diagrams for these highly artificial numerical systems have many peaks and troughs compared to measurements on natural samples due to the discrete responses of individual grains to local interaction fields.…”

Section: Simulated Hysteresis and Forc Responses Of Individual Framboidssupporting

confidence: 79%

“…The FORC response of a simulated clustered greigite ensemble (Fig. 4) contrasts with that of isolated SD and SV grains (Valdez-Grijalva et al, 2018a). Isolated SD greigite particles produce FORC signals with a characteristic boomerang shape, strong B u = 0 contributions and a tilted negative ridge, while SV grains produce a more complex pattern.…”

Section: Discussionmentioning

confidence: 97%

“…These studies examined the effect of grain size, and identified the transition size for stable single-domain (SD) to singlevortex (SV) behaviour (∼54 − 70 nm for equidimensional grains); at this threshold size the magnetic structure becomes non-uniform and the magnetic response changes markedly. Numerical simulations have been performed for hysteresis and first-order reversal curve (FORC) properties of non-interacting SD and SV greigite dispersions (Valdez-Grijalva et al, 2018a;Valdez-Grijalva and Muxworthy, 2019); however, the FORC properties of highly interacting greigite ensembles remain poorly understood. FORC diagrams are routinely used in environmental magnetism and palaeomagnetism to identify magnetic minerals (Roberts et al, 2014(Roberts et al, , 2018b.…”

Section: Introductionmentioning

confidence: 99%

“…In this paper, we use a numerical micromagnetic finite element method (FEM) model to calculate the FORC response of framboidal greigite composed of highly interacting, close-packed 30 nm grains. At this size, isolated equidimensional grains can only occur in the SD state (Valdez-Grijalva et al, 2018a) and produce FORC signals characteristic of isolated SD grains with cubic magnetocrystalline anisotropy (Valdez-Grijalva et al, 2018a).…”

Section: Introductionmentioning

confidence: 99%

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Micromagnetic simulations of first-order reversal curve (FORC) diagrams of framboidal greigite

Valdez-Grijalva

Nagy

Muxworthy

et al. 2020

Geophysical Journal International

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SUMMARY Greigite is a sensitive environmental indicator and occurs commonly in nature as magnetostatically interacting framboids. Until now only the magnetic response of isolated non-interacting greigite particles have been modelled micromagnetically. We present here hysteresis and first-order reversal curve (FORC) simulations for framboidal greigite (Fe3S4), and compare results to those for isolated particles of a similar size. We demonstrate that these magnetostatic interactions alter significantly the framboid FORC response compared to isolated particles, which makes the magnetic response similar to that of much larger (multidomain) grains. We also demonstrate that framboidal signals plot in different regions of a FORC diagram, which facilitates differentiation between framboidal and isolated grain signals. Given that large greigite crystals are rarely observed in microscopy studies of natural samples, we suggest that identification of multidomain-like FORC signals in samples known to contain abundant greigite could be interpreted as evidence for framboidal greigite.

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Section: Simulated Hysteresis and Forc Responses Of Individual Framboidssupporting

confidence: 79%

Section: Discussionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Micromagnetic simulations of first-order reversal curve (FORC) diagrams of framboidal greigite

Valdez-Grijalva

Nagy

Muxworthy

et al. 2020

Geophysical Journal International

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“…In the absence of thermal activation, transient hysteresis is primarily associated with irreversible changes in magnetization driven by self-demagnetizing fields (Fabian, 2003). Zhao et al (2017) associated bilobate structures in tFORC diagrams with vortex state nucleation and annihilation, in agreement with both theoretical modeling and empirical observations of materials dominated by vortex states (Pike & Fernandez, 1999;Dumas et al, 2007;Roberts et al, 2017;Valdez-Grijalva et al, 2018;Lascu et al, 2018).…”

Section: Physical Origins Of Remforc Iforc and Tforc Signals 411supporting

confidence: 77%

Simulation of Remanent, Transient, and Induced FORC Diagrams for Interacting Particles With Uniaxial, Cubic, and Hexagonal Anisotropy

Harrison

Zhao

et al. 2019

JGR Solid Earth

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The diagnostic power of first‐order reversal curve (FORC) diagrams has recently been enhanced by an extended measurement protocol that yields three additional FORC‐like diagrams: the remanent (remFORC), induced (iFORC), and transient (tFORC) diagrams. Here, we present micromagnetic simulations using this extended protocol, including numerical predictions of remFORC, iFORC, and tFORC signatures for particle ensembles relevant to rock magnetism. Simulations are presented for randomly packed single‐domain (SD) particles with uniaxial, cubic, and hexagonal anisotropy, and for chains of uniaxial SD particles. Noninteracting particles have zero tFORC, but distinct remFORC and iFORC signals, that provide enhanced discrimination between uniaxial, cubic, and hexagonal anisotropy types. Increasing interactions lessen the ability to discriminate between uniaxial and cubic anisotropy but reproduces a change in the pattern of positive and negative iFORC signals observed for SD‐dominated versus vortex‐dominated samples. Interactions in SD particles lead to the emergence of a bi‐lobate tFORC distribution, which is related to formation of flux‐closure in super‐vortex states. A predicted iFORC signal associated with collapsed chains is observed in experimental data and may aid magnetofossil identification in sediments. Asymmetric FORC and FORC‐like distributions for hexagonal anisotropy are explained by the availability of multiple easy axes within the basal plane. A transition to uniaxial switching occurs below a critical value of the out‐of‐plane/in‐plane anisotropy ratio, which may allow FORC diagrams to provide insight into the stress state of hexagonal minerals, such as hematite.

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Multilayer regular hexagonal prism barium ferrite nanodot arrays on a substrate based on an AAO mask

Zheng

Luo

et al. 2021

Chemical Physics Letters

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Magnetic vortex effects on first-order reversal curve (FORC) diagrams for greigite dispersions

Cited by 26 publications

References 37 publications

Micromagnetic simulations of first-order reversal curve (FORC) diagrams of framboidal greigite

Micromagnetic simulations of first-order reversal curve (FORC) diagrams of framboidal greigite

Simulation of Remanent, Transient, and Induced FORC Diagrams for Interacting Particles With Uniaxial, Cubic, and Hexagonal Anisotropy

Multilayer regular hexagonal prism barium ferrite nanodot arrays on a substrate based on an AAO mask

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