FORCulator: A micromagnetic tool for simulating first‐order reversal curve diagrams

Harrison, R. J.; Lascu, Ioan

doi:10.1002/2014gc005582

Cited by 63 publications

(131 citation statements)

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“…As observed above, offset peaks in FORC diagrams have been reported in a variety of natural materials (pyrrhotite, greigite, and single‐phase hematite) that have, in common, strong magnetocrystalline anisotropy that dominates switching behavior. Harrison and Lascu [] were also able to replicate an offset peak and associated negative trough, both with a negative slope, in simulations of SD particles with cubic anisotropy alone. In SD particles where magnetocrystalline anisotropy is dominant, multiple magnetization states are possible intermediate to plus or minus saturation, which if measured as a minor loop may have switching fields that are not equal and opposite [ Usov and Peschany , ].…”

Section: Discussionmentioning

confidence: 99%

Nonlinear Preisach maps: Detecting and characterizing separate remanent magnetic fractions in complex natural samples

Church¹,

Fabian

McEnroe³

2016

JGR Solid Earth

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Natural remanent magnetization carriers in rocks can contain mixtures of magnetic minerals that interact in complex ways and are challenging to characterize by current measurement techniques. Here a nonlinear mapping scheme is described that efficiently enhances sensitivity and the resolution power of remanent Preisach maps. Using this scheme a large dynamic range of magnetic moments and coercivities can be reliably resolved. The method is applied to synthetic and natural standard samples containing magnetite and hematite, as well as to natural samples from remanent magnetic anomalies where complex microstructures are observed. It is shown that certain offset high‐coercivity patterns in remanent Preisach maps may serve as fingerprints for exsolution structures of ilmenite in hematite or hematite in ilmenite and that in some magnetite‐bearing remanent anomalies the magnetite coercivity is increased beyond its intrinsic coercivity range. Experimental results and theoretical considerations indicate a minimal coercivity of about 10 mT for single‐domain (SD) magnetite, such that observation of lower coercivities implies pseudo‐SD (PSD) or multidomain grain sizes. A diagnostic hematite pattern with a peak downward offset of 17 ± 2% of the intrinsic coercivity is found that is stable over a large range of intrinsic coercivities and may be related to shielding of internal defect or lamellar moments by a spin canting response to the internal field.

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Section: Discussionmentioning

confidence: 99%

Nonlinear Preisach maps: Detecting and characterizing separate remanent magnetic fractions in complex natural samples

Church¹,

Fabian

McEnroe³

2016

JGR Solid Earth

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“…Likewise, identifying the magnetic domain state for some magnetic mineral configurations presents challenges, and contrasting results can be obtained when analyzed with different methods, such as double or multiple magnetosome chain bundles even though individual magnetosome crystals have stable SD properties. Micromagnetic simulations of frustrated systems (Harrison, ), particles with complex geometries (Lascu et al, ; Williams et al, , ), and strongly interacting particle assemblages/magnetofossil chains (Chang et al, ; Evans et al, ; Harrison & Lascu, ; Muxworthy et al, ) have improved our theoretical understanding of these issues and are enabling more nuanced interpretations of domain states, which takes us beyond the simple SD‐PSD‐MD designation. These challenges should be grappled with when relevant; nevertheless, routine domain state diagnosis of geological materials remains fundamentally important in paleomagnetism and environmental magnetism.…”

Section: Is Magnetic Domain State Identification a Chimera?mentioning

confidence: 99%

“…Particles near the SP/SD threshold size commonly give rise to a secondary peak near the origin of the FORC diagram with a dominant vertical response near the B i axis in the lower FORC half‐plane (e.g., Figure c; Pike et al, ). In addition to providing information about domain state, Harrison and Lascu () demonstrated that FORC diagrams provide information about the type of magnetocrystalline anisotropy within magnetic particles, which provides further valuable information. Details concerning FORC diagrams and the manifestations of each domain state are provided by Roberts et al ().…”

Section: Candidate Approaches For Domain State Diagnosismentioning

confidence: 99%

Domain State Diagnosis in Rock Magnetism: Evaluation of Potential Alternatives to the Day Diagram

Roberts

Harrison

et al. 2019

JGR Solid Earth

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The Day diagram is used extensively in rock magnetism for domain state diagnosis. It has been shown recently to be fundamentally ambiguous for 10 sets of reasons. This ambiguity highlights the urgency for adopting suitable alternative approaches to identify the domain state of magnetic mineral components in rock magnetic studies. We evaluate 10 potential alternative approaches here and conclude that four have value for identifying data trends, but, like the Day diagram, they are affected by use of bulk parameters that compromise domain state diagnosis in complex samples. Three approaches based on remanence curve and hysteresis loop unmixing, when supervised by independent data to avoid nonuniqueness of solutions, provide valuable component‐specific information that can be linked by inference to domain state. Three further approaches based on first‐order reversal curve diagrams provide direct domain state diagnosis with varying effectiveness. Environmentally important high‐coercivity hematite and goethite are represented with variable effectiveness in the evaluated candidate approaches. These minerals occur predominantly in noninteracting single‐domain particle assemblages in paleomagnetic contexts, so domain state diagnosis is more critical for ferrimagnetic minerals. Treating the high‐coercivity component separately following normal rock magnetic procedures allows focus on the more vexing problem of diagnosing domain state in ferrimagnetic mineral assemblages. We suggest a move away from nondiagnostic methods based on bulk parameters and adoption of approaches that provide unambiguous component‐specific domain state identification, among which various first‐order reversal curve‐based approaches provide diagnostic information.

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“…All FORC diagrams were processed using the VARIFORC function in FORCinel, 22,23 which is written in Igor (V2.02 in IGOR Pro7, WaveMetrics, Portland, OR). In processing the FORC data, the lower edge artifact was removed 24 prior to plotting the FORC diagram. Ⅲ. RESULTS…”

Section: A Theory and Simulationmentioning

confidence: 99%

Multiphase magnetic systems: Measurement and simulation

Cao

Ahmadzadeh

et al. 2018

Journal of Applied Physics

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Multiphase magnetic systems are common in nature and are increasingly being recognized in technical applications. One characterization method which has shown great promise for determining separate and collective effects of multiphase magnetic systems is first order reversal curves (FORCs). Several examples are given of FORC patterns which provide distinguishing evidence of multiple phases. In parallel, a visualization method for understanding multiphase magnetic interaction is given, which allocates Preisach magnetic elements as an input 'Preisach hysteron distribution pattern' (PHDP) to enable simulation of different 'wasp-waisted' magnetic behaviors. These simulated systems allow reproduction of different major hysteresis loop, FORC pattern, and switching field distributions of real systems and parameterized theoretical systems.The experimental FORC measurements and FORC diagrams of four commercially obtained magnetic materials, particularly those sold as nanopowders, shows that these materials are often not phase pure. They exhibit complex hysteresis behaviors that are not predictable based on relative phase fraction obtained by characterization methods such as diffraction. These multiphase materials, Even though the ideal characteristics of hysteresis in perfect single magnetic domains is generally accepted, it is still a challenge to interpret the hysteresis of real materials, as it depends on particle size, shape, and distribution, as well as stress, defects, and impurities. The hysteresis of magnetic mixtures is even more complex, as interactions between non-dilute phases distort the simple loop shape. However, the parameters extracted from major hysteresis loop -for instance, coercivityare not very efficient at showing the interactions of magnetic phases in a multiphase system. First order reversal curve (FORC) analysis is one technique which has developed rapidly in the last two decades, 1 providing a powerful tool for observing magnetic switching contributed by different magnetic phases. FORC is now applied to understand various hysteretic behaviors in metalinsulator transitions, 2 ferroelectricity, 3 magnetocalorics, 4 and perpendicular magnetic recording media. 5 The FORC technique can also be employed to distinguish the different magnetic signals in multiphase systems 4,6 to investigate subtle magnetic features caused by interaction of multiple magnetic phases.In this paper, a series of multiphase magnetic nanopowders are investigated experimentally using major hysteresis loops and FORC diagrams and these systems are also modeled using 'Preisach hysteron distribution patterns' (PHDPs) based on the classical Preisach model (CPM) to aid in descriptive understanding of the reduction of coercivity, or 'wasp-waistedness' features, observed in major loops of multiphase materials. The FORC diagrams of them generally indicate the existence of a low coercivity phase, a high coercivity phase, and a coupling region, which can all be simulated using PHDPs. Together, the simulations and measurements pr...

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FORCulator: A micromagnetic tool for simulating first‐order reversal curve diagrams

Cited by 63 publications

References 54 publications

Nonlinear Preisach maps: Detecting and characterizing separate remanent magnetic fractions in complex natural samples

Nonlinear Preisach maps: Detecting and characterizing separate remanent magnetic fractions in complex natural samples

Domain State Diagnosis in Rock Magnetism: Evaluation of Potential Alternatives to the Day Diagram

Multiphase magnetic systems: Measurement and simulation

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