First-order reversal curve (FORC) diagrams of nanomagnets with cubic magnetocrystalline anisotropy: A numerical approach

Valdez-Grijalva, Miguel A.; Muxworthy, Adrian R.

doi:10.1016/j.jmmm.2018.09.086

Cited by 21 publications

(27 citation statements)

References 15 publications

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“…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%

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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: Introductionmentioning

confidence: 99%

“…and Muxworthy, 2019;Valdez-Grijalva et al, 2018a). Then, the spherical triangle is subdivided into roughly equal trianglular sub-units to obtain 85 triangular cells; this was found to accurately represent a random distribution over the whole sphere.…”

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confidence: 99%

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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“…These diagrams are attractive since the FORC distribution is expected to provide detailed information of the interaction field and its effects in particle assemblies 1 and under some circumstances, they allow to reconstruct the intrinsic properties of fine particle systems 26 . In non-interacting particle assemblies, the FORC diagram shows a single narrow distribution, or ridge, along the axis and in this case, it represents the intrinsic coercive field distribution (CFD) 14 , 19 , 27 , 28 . However, in assemblies of interacting particles, the interaction field modifies the width of the CFD, hereafter referred to as , and leads to a second ridge along the axis, known as the interaction field distribution (IFD), whose width, , has been shown to vary with the strength of the interaction field 1 , 19 , 26 , 27 , 29 , 30 .…”

Section: Introductionmentioning

confidence: 99%

Relation of the average interaction field with the coercive and interaction field distributions in First order reversal curve diagrams of nanowire arrays

Velázquez

Guerrero

Martínez

et al. 2020

Sci Rep

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First-order reversal curve diagrams, or FORC diagrams, have been studied to determine if the widths of their distributions along the interaction and coercivity axes can be related to the mean-field magnetization dependent interaction field (MDIF). Arrays of nanowires with diameters ranging from 18 up to 100 nm and packing fractions varying from 0.4 to 12% have been analyzed. The mean-field MDIF has been measured using the remanence curves and used as a measuring scale on the FORC diagrams. Based on these measurements, the full width of the interaction field distribution and the full width at half maximum (FWHM) of the FORC distribution profile along the interaction field direction are shown to be proportional to the MDIF, and the relation between them is found. Moreover, by interpreting the full width of the coercive field distribution in terms of the dipolar induced shearing, a simple relation is found between the width of this distribution and the MDIF. Furthermore, we show that the width of the FORC distribution along the coercive field axis is equal to the width of the switching field distribution obtained by the derivation of the DC remanence curve. This was further verified with the switching field distribution determined using in-field magnetic force microscopy (MFM) for very low density nanowires. The results are further supported by the good agreement found between the experiments and the values calculated using the mean-field model, which provides analytical expressions for both FORC distributions.

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“…The multiaxial magnetocrystalline anisotropy as a characteristic trait of 4C pyrrhotite (Koulialias, Charilaou, Schäublin, et al, ) could be a cause for the peculiar negative slope in the FORC diagram (cf. Valdez‐Grijalva & Muxworthy, ). Such slope was yielded from authigenic pyrrhotite phases in sedimentary gas hydrate‐bearing deposits (e.g., Horng, ; Kars & Kodama, ) and from a mechanically treated 4C pyrrhotite particle fraction of <5 μm (Wehland et al, ).…”

Section: Resultsmentioning

confidence: 99%

The Besnus Transition in Single‐Domain 4C Pyrrhotite

Koulialias

Lesniak

Schwotzer

et al. 2019

Geochem Geophys Geosyst

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The discontinuous change in magnetic properties at a temperature of about 32 K, denoted as the Besnus transition, is a diagnostic feature for detecting 4C pyrrhotite in geological systems. The transition is grain size dependent, and it has been assumed that the single‐domain (SD) to multidomain (MD) threshold is in the micron size range. Here we present a combined crystallographic and magnetic study of a pure phase, SD 4C pyrrhotite that was produced by ball milling of a MD precursor. The mechanical treatment generated varying grain sizes of less than 20 μm, which are solely in a SD magnetic state. It also decreases the coherent scattering domains of the grains from 216 nm in the MD sample to 30 nm, which is taken to set limits for the MD/SD threshold in 4C pyrrhotite grains. The alternating current susceptibility response associated with the Besnus transition is diagnostic for distinguishing SD and MD 4C pyrrhotite. The unambiguous identification of SD 4C pyrrhotite provides a better insight into its occurrence in geological systems.

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First-order reversal curve (FORC) diagrams of nanomagnets with cubic magnetocrystalline anisotropy: A numerical approach

Cited by 21 publications

References 15 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

Relation of the average interaction field with the coercive and interaction field distributions in First order reversal curve diagrams of nanowire arrays

The Besnus Transition in Single‐Domain 4C Pyrrhotite

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