The meaning of maxima and minima in first order reversal curves: Determining the interaction between species in a sample

Moreno, R.; Williams, Wyn; Muxworthy, Adrian R.; Paterson, Greig A.; Heslop, David

doi:10.1016/j.jmmm.2022.170042

Cited by 2 publications

(4 citation statements)

References 34 publications

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“…These noisy tails are often seen in experimental FORCs and appear also in our models. The cause in both cases is the same, and are due to slightly different switching fields observed across multiple reversal curves (Moreno-Ortega et al, 2022).…”

Section: Equant Truncated-octahedral Particles Of Magnetitementioning

confidence: 86%

“…These differences are caused by the stronger planar anisotropy of the oblate particles, which encourages the spontaneous formation of SV states from the saturated SD states as the field is reduced. Similarly the positive lobe below the B c axis corresponds to nucleation of the SV state (Dumas et al, 2007;Moreno-Ortega et al, 2022). However, nucleation of the SV state does not occur directly from SD, but via an inhomogeneous magnetic structure where there is some flowering of the surface magnetization together with planar rotation of the magnetization within the particles.…”

Section: Oblate Truncated-octahedral Particles Of Magnetitementioning

confidence: 99%

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Micromagnetic determination of the FORC response of paleomagnetically significant magnetite assemblages

Nagy,

Moreno,

Muxworthy

et al. 2024

Preprint

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Micromagnetic modelling allows the systematic study of the effects of particle size and shape on the first-order reversal curve (FORC) magnetic hysteresis response for magnetite particles in the single-domain (SD) and pseudo-single domain (PSD) particle size range. The interpretation of FORCs, though widely used, has been highly subjective. Here, we use micromagnetics to model randomly oriented distributions of particles to allow more physically meaningful interpretations. We show that one commonly found type of PSD particle - namely single vortex (SV) particles - has far more complex signals than SD particles, with multiple peaks and troughs in the FORC distribution, where the peaks have higher switching fields for larger SV particles. Particles in the SD to SV transition zone have the lowest switching fields. Symmetrical and prolate particles display similar behavior, with distinctive peaks forming near the vertical axis of the FORC diagram. In contrast, highly oblate particles produce ‘butterfly’ structures, suggesting that these are potentially diagnostic of particle morphology. We also consider FORC diagrams for distributions of particle sizes and shapes and produce an online application that users can use to build their own FORC distributions. There is good agreement between the model predictions for distributions of particle sizes and shapes, and the published experimental literature.

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Section: Equant Truncated-octahedral Particles Of Magnetitementioning

confidence: 86%

Section: Oblate Truncated-octahedral Particles Of Magnetitementioning

confidence: 99%

Micromagnetic determination of the FORC response of paleomagnetically significant magnetite assemblages

Nagy,

Moreno,

Muxworthy

et al. 2024

Preprint

View full text Add to dashboard Cite

show abstract

“…One source of these features could be polynomial ringing—where the second‐degree polynomial approximation to the magnetization surface in a series of FORC curves results in overfitting. Analysis of the polynomial fit leads us to conclude that these features are more likely due to slightly different switching fields observed across multiple reversal curves (Moreno et al., 2022). We note that small scale features such as VNAPs and the mottled regions highlighted above may be further smoothed in natural specimens that contain a broader distribution of size and shape than presented in this study.…”

Section: Simulated Forc Diagrams For Random Distributionsmentioning

confidence: 99%

“…These differences are caused by the stronger planar anisotropy of the oblate particles, which encourages the spontaneous formation of SV states from the saturated SD states as the field is reduced. Similarly the positive lobe below the B c axis corresponds to nucleation of the SV state (Dumas et al, 2007;Moreno et al, 2022). However, nucleation of the SV state does not occur directly from SD, but via an inhomogeneous magnetic structure where there is some flowering of the surface magnetization together with planar rotation of the magnetization within the particles.…”

Section: Oblate Truncated-octahedral Particles Of Magnetitementioning

confidence: 99%

Micromagnetic Determination of the FORC Response of Paleomagnetically Significant Magnetite Assemblages

Nagy,

Moreno,

Muxworthy

et al. 2024

Geochem Geophys Geosyst

Self Cite

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Micromagnetic modeling allows the systematic study of the effects of particle size and shape on the first‐order reversal curve (FORC) magnetic hysteresis response for magnetite particles in the single‐domain (SD) and pseudo‐single domain (PSD) particle size range. The interpretation of FORCs, though widely used, has been highly subjective. Here, we use micromagnetics to model randomly oriented distributions of particles to allow more physically meaningful interpretations. We show that one commonly found type of PSD particle—namely the single vortex (SV) particle—has far more complex signals than SD particles, with multiple peaks and troughs in the FORC distribution, where the peaks have higher switching fields for larger SV particles. Particles in the SD to SV transition zone have the lowest switching fields. Symmetrical and prolate particles display similar behavior, with distinctive peaks forming near the vertical axis of the FORC diagram. In contrast, highly oblate particles produce “butterfly” structures, suggesting that these are potentially diagnostic of particle morphology. We also consider FORC diagrams for distributions of particle sizes and shapes and produce an online application that users can use to build their own FORC distributions. There is good agreement between the model predictions for distributions of particle sizes and shapes, and the published experimental literature.

show abstract

The meaning of maxima and minima in first order reversal curves: Determining the interaction between species in a sample

Cited by 2 publications

References 34 publications

Micromagnetic determination of the FORC response of paleomagnetically significant magnetite assemblages

Micromagnetic determination of the FORC response of paleomagnetically significant magnetite assemblages

Micromagnetic Determination of the FORC Response of Paleomagnetically Significant Magnetite Assemblages

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