Magnetic record of deglaciation using FORC-PCA, sortable-silt grain size, and magnetic excursion at 26 ka, from the Rockall Trough (NE Atlantic)

Channell, J. E. T.; Harrison, R. J.; Lascu, Ioan; McCave, I Nick; Hibbert, Fiona D.; Austin, Wen

doi:10.1002/2016gc006300

Cited by 46 publications

(47 citation statements)

References 98 publications

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“…Documentation of widespread SD nanoparticles as inclusions within host silicates in the geological record provides support for this possibility (Chang et al, ; Evans et al, ). FORC unmixing (Channell et al, ; Lascu et al, ) now makes it possible, along with the additional FORC measurements of Zhao et al (), to discriminate SD, vortex, and MD moments in natural samples. Regardless of the possible presence of SD grains, particle size and shape variations are widespread in natural samples and are likely to be responsible for smooth magnetic property variations throughout the PSD size range.…”

Section: Discussionmentioning

confidence: 99%

Resolving the Origin of Pseudo‐Single Domain Magnetic Behavior

et al. 2017

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The term “pseudo‐single domain” (PSD) has been used to describe the transitional state in rock magnetism that spans the particle size range between the single domain (SD) and multidomain (MD) states. The particle size range for the stable SD state in the most commonly occurring terrestrial magnetic mineral, magnetite, is so narrow (~20–75 nm) that it is widely considered that much of the paleomagnetic record of interest is carried by PSD rather than stable SD particles. The PSD concept has, thus, become the dominant explanation for the magnetization associated with a major fraction of particles that record paleomagnetic signals throughout geological time. In this paper, we argue that in contrast to the SD and MD states, the term PSD does not describe the relevant physical processes, which have been documented extensively using three‐dimensional micromagnetic modeling and by parallel research in material science and solid‐state physics. We also argue that features attributed to PSD behavior can be explained by nucleation of a single magnetic vortex immediately above the maximum stable SD transition size. With increasing particle size, multiple vortices, antivortices, and domain walls can nucleate, which produce variable cancellation of magnetic moments and a gradual transition into the MD state. Thus, while the term PSD describes a well‐known transitional state, it fails to describe adequately the physics of the relevant processes. We recommend that use of this term should be discontinued in favor of “vortex state,” which spans a range of behaviors associated with magnetic vortices.

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Section: Discussionmentioning

confidence: 99%

Resolving the Origin of Pseudo‐Single Domain Magnetic Behavior

et al. 2017

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“…For example, the commonly observed central ridge signature in sedimentary samples is used widely as an indicator of the presence of noninteracting biogenic magnetic minerals [e.g., Chen et al , ; Egli et al , ; Roberts et al , ; Yamazaki and Ikehara , ; Heslop et al , ]. FORC diagrams are also being used increasingly in a more quantitative manner through calculation of theoretical FORC distributions for individual components and initial attempts at component‐by‐component unmixing [ Egli et al , ; Harrison and Lascu , ; Heslop et al , ; Lascu et al , ; Channell et al , ].…”

Section: Introductionmentioning

confidence: 99%

Magnetic domain state diagnosis using hysteresis reversal curves

et al. 2017

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We present results for a series of hysteresis measurements that provide information about remanent, induced, transient‐free, and transient magnetization components. These measurements, and differences between measurement types, enable production of six types of first‐order reversal curve (FORC)‐like diagrams which only double the number of measurements involved in a conventional FORC measurement. These diagrams can be used to distinguish magnetic signatures associated with each domain state. When analyzing samples with complex magnetic mineral mixtures, the contrasting domain state signatures are mixed together in a traditional FORC diagram, but these signatures can be identified individually when using the various FORC diagrams discussed here. The ability to make different FORC measurements and to identify separately each magnetic component by investigating different magnetization types can provide much‐improved understanding of the information provided by FORC diagrams. In particular, the transient hysteresis FORC diagram provides a method to measure the nucleation field of magnetic vortices and domain walls. We provide a simple explanation for FORC results from natural multidomain samples that are not explained by conventional domain wall pinning models. We also provide software for processing the different types of FORC data.

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“…by numerically fitting experimental TA-FORCs to simulations or by using PCA (Channell et al, 2016;Harrison et al, 2018;Heslop et al, 2014;Lascu et al, 2015). While presently FORC diagrams are mainly used to assess domain states and interactions only, they also contain information about the thermal fluctuation fields of the sample's magnetic constituents.…”

Section: Discussionmentioning

confidence: 99%

“…In principle, the FORC signatures of two grain/mineral populations in a single sample could thus be studied independently, either qualitatively by visual inspection of the FORC diagram, or quantitatively by methods such as FORC-PCA (Channell et al, 2016;Harrison et al, 2018;Lascu et al, 2015;Roberts et al, 2018). In principle, the FORC signatures of two grain/mineral populations in a single sample could thus be studied independently, either qualitatively by visual inspection of the FORC diagram, or quantitatively by methods such as FORC-PCA (Channell et al, 2016;Harrison et al, 2018;Lascu et al, 2015;Roberts et al, 2018).…”

Section: Potential Of Distinguishing Grain Populations In a Single Samentioning

confidence: 99%

“…FORCs are a set of partial hysteresis loops that are measured by reducing an applied field from saturation to a reversal field H a and then measuring a partial hysteresis loop while increasing the field H b backup. Often, this is done qualitatively by visual inspection, but recently also quantitatively using principal component analysis (PCA) to unmix contributions of different magnetic constituents (Channell et al, 2016;Harrison et al, 2018;Lascu et al, 2015;Roberts et al, 2018). FORC diagrams have been successful at characterizing domain states of samples, for example, distinguishing pseudo-single-domain (PSD) behavior from mixtures of single-domain (SD) and multidomain (MD) behavior (Muxworthy et al, 2005), magnetic mineral identification (Egli et al, 2010;Roberts et al, 2006), and at providing insights into variations of environmental magnetic records (e.g., Chang et al, 2014Chang et al, , 2016Channell et al, 2016;Hatfield et al, 2017;Yamazaki, 2009), among others (see Roberts et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

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Time‐Asymmetric FORC Diagrams: A New Protocol for Visualizing Thermal Fluctuations and Distinguishing Magnetic Mineral Mixtures

Berndt

Chang

Wang

et al. 2018

Geochem Geophys Geosyst

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First‐order reversal curves (FORCs) are nowadays routinely used to assess domain states and magnetostatic interactions of magnetic minerals. While a huge step forward from bulk magnetic measurements in terms of sample characterization, there is a missing link between the FORC diagrams and remanence behavior: FORC diagrams mainly reveal domain states, while remanence behavior is largely controlled by thermal activations. We present a new tool to visualize thermal fluctuations in so‐called time‐asymmetric (TA) FORC diagrams. TA‐FORCs differ from traditional FORCs in that they maintain the reversal field Ha for a longer time (minutes) than the FORC measurement field Hb (milliseconds). During this extended hold time, thermal activations cause some magnetic grains to change their magnetization, giving rise to an upward shift in the FORC diagram. The magnitude of this shift gives insight into the thermoviscous stability of the mineral and its remanence acquisition behavior. This not only allows to distinguish thermoviscous effects in FORC diagrams from magnetostatic (i.e., interactions/domain state related) effects but also provides a way to separate mixtures of magnetic minerals: two minerals with similar coercivity spectra that would totally overlap in traditional FORC diagrams show different upward shifts in TA‐FORC diagrams, which in some cases enable complete separation of the minerals visually. This effectively provides two independent FORC signatures for two magnetic constituents in a sample such as two grain populations of different grain sizes, grain shapes, and/or mineral.

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Magnetic record of deglaciation using FORC-PCA, sortable-silt grain size, and magnetic excursion at 26 ka, from the Rockall Trough (NE Atlantic)

Cited by 46 publications

References 98 publications

Resolving the Origin of Pseudo‐Single Domain Magnetic Behavior

Resolving the Origin of Pseudo‐Single Domain Magnetic Behavior

Magnetic domain state diagnosis using hysteresis reversal curves

Time‐Asymmetric FORC Diagrams: A New Protocol for Visualizing Thermal Fluctuations and Distinguishing Magnetic Mineral Mixtures

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