Analysis of hysteresis curves of samples with magnetite and hematite grains

Hejda, Pavel; Kapička, A.; Petrovský, Eduard; Sjöberg, Bo A.

doi:10.1109/20.312434

Cited by 11 publications

(7 citation statements)

References 2 publications

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“…This principle of additivity was also invoked by Becker [1982] to explain wasp-waisted hysteresis behavior observed from a permanent rare earth magnet (Figure 3b). Bean [1955] and Parry [1980Parry [ , 1982 showed that, in the absence of magnetic interactions between particles, the magnetization in a given field is simply the sum of the magnetization of the isolated particles in that field (nonadditivity will result at concentrations of a few percent, by volume, as is evident in the work of Hejda et al [ 1994]). We have used this principle to extend the work of Wasilewski [1973] by measuring separate samples of known narrow grain size, using the same applied field at each step.…”

Section: Mixtures Of Magnetic Grain Sizesmentioning

confidence: 99%

Wasp‐waisted hysteresis loops: Mineral magnetic characteristics and discrimination of components in mixed magnetic systems

Roberts¹,

Cui²,

Verosub³

1995

J. Geophys. Res.

530

305

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Rock magnetic studies of complex systems that contain mixtures of magnetic minerals or mixed grain size distributions have demonstrated the need for a better method of distinguishing between different magnetic components in geological materials. Hysteresis loops that are constricted in the middle section, but are wider above and below the middle section, are commonly observed in mixed magnetic assemblages. Such “wasp‐waisted” hysteresis loops have been widely documented, particularly with respect to rare earth permanent magnets, basaltic lava flows, remagnetized Paleozoic carbonate rocks, and an increasingly wide range of other rocks. Our modelling, combined with a review of previous work, indicates that there are several conditions that give rise to, as well as magnetic properties that are characteristic of, wasp‐waisted hysteresis loops. First, at least two magnetic components with strongly contrasting coercivities must coexist. This condition can arise from either mixtures of grain sizes of a single magnetic mineral, or a combination of magnetic minerals with contrasting cocrcivities, or a combination of these two situations. Second, materials that give rise to wasp‐waisted hysteresis loops will have relatively high ratios of the coercivity of remanence to coercive force (Bcr/Bc) because B0 is controlled by the soft (low coercivity) component, whereas Bcr is controlled by the hard (high coercivity) component. Third, values of Bcr/Bc ≥ 10 usually only occur for strongly wasp‐waisted loops when the low coercivity component comprises an overwhelmingly large fraction of the total volume of magnetic grains. Fourth, a given mixture of superparamagnetic and single‐domain (SD) grains is more likely to give rise to wasp‐waisted hysteresis loops than an equivalent mixture of SD and multidomain grains. Fifth, our results provide empirical confirmation that the total magnetization of a material is the sum of the weighted contributions of each component, in the absence of significant magnetic interaction between particles. Thus to contribute significantly to wasp‐waisted behavior, a mineral magnetic component must give rise to a significant portion of the total magnetization of the rock. As a result, minerals with weak magnetic moments such as hematite need to occur in large concentrations to cause wasp‐waistedness in materials that also contain ferrimagnetic minerals. We outline a method for determining the magnetic components that can give rise to wasp‐waisted hysteresis loops. This method is based on high‐ and low‐temperature magnetic measurements that are used to identify the dominant remanence‐bearing mineral/s and on mineral magnetic techniques that are used to discriminate between different magnetic domain states. The method is illustrated with several examples from archaeological, geological, and synthetic materials.

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Section: Mixtures Of Magnetic Grain Sizesmentioning

confidence: 99%

Wasp‐waisted hysteresis loops: Mineral magnetic characteristics and discrimination of components in mixed magnetic systems

Roberts¹,

Cui²,

Verosub³

1995

J. Geophys. Res.

530

305

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“…Little investigation has been done on the mixing of minerals or environmental sources such as soil, rocks and anthropogenic sources such as spoil heaps and atmospheric fly-ash contributions, which may contribute to sediment mixtures. Mixing of synthetic minerals such as haematite and magnetite has proved difficult as the strength of the ferrimagnetic components, unless diluted to minute amounts (< 1 per cent), masks the canted-antiferromagnetic property (c& Hejda et al 1992).…”

Section: Introductionmentioning

confidence: 99%

Mineral magnetic properties of mixtures of environmental and synthetic materials: linear additivity and interaction effects

Lees

1997

Geophysical Journal International

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S U M M A R YMineral magnetic properties have been used recently to classify and to attempt to quantify the sources of sediments through environmental systems. Linear modelling techniques could be used with a wide range of concentration-dependent magnetic measurements to quantify the sources of sediments. To investigate wider application of linear modelling techniques using mineral magnetic properties, research has been conducted using laboratory mixtures of up to six source materials, including both natural environmental materials and synthetic compounds. While six sources may seem ambitious, this figure was used as an absolute upper limit rather than giving a real prospect of mathematically unmixing six sources. It has been found that even with the most magnetically differentiable materials, large errors are encountered when modelling the sources of the mixtures. This paper investigates the causes of 'non-additivity' of certain magnetic measurements and the failure of the linear modelling of the sources of the mixtures. Possible reasons for this failure include source homogeneity, calibration and linearity of equipment, magnetic viscosity of materials and/or the changing physical characteristics of the source materials once mixed together (interaction effects). In testing linear additivity, low-frequency susceptibility is the most reliable mineral magnetic measurement, while remanence measurements suffer from a systematic error in the expected results. Results have shown that in the best controlled conditions where the sources are identified and are artificially mixed together, the results of linear modelling are quite poor and at best four sources can be 'unmixed' with reasonable success. It is suggested that interaction within the mixtures, especially when containing highly ferrimagnetic burnt environmental materials, causes some of the non-additivity phenomena.

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“…Hejda et al. (1994) found that the overall hysteresis loops for magnetite and hematite mixtures do not represent a simple sum of contributions corresponding to individual components. Muxworthy et al.…”

Section: Introductionmentioning

confidence: 99%

“…Quantifying contributions from hematite within artificial magnetite/hematite mixtures is challenging. Hejda et al (1994) found that the overall hysteresis loops for magnetite and hematite mixtures do not represent a simple sum of contributions corresponding to individual components. Muxworthy et al (2005) measured FORC diagrams for artificial magnetite/hematite mixtures and found critical concentrations at which the magnetite signal swamped the hematite signal, rendering the hematite undetectable.…”

mentioning

confidence: 99%

Assessment of Magnetic Techniques for Understanding Complex Mixtures of Magnetite and Hematite: The Inuyama Red Chert

Oda

Zhao

et al. 2021

JGR Solid Earth

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Magnetite and hematite mixtures occur widely in nature. Magnetic unmixing of the signals recorded by these minerals can be important for assessing the origin of their respective paleomagnetic remanences and for extracting geological and paleoenvironmental information. However, unmixing magnetic signals from complex magnetite and hematite mixtures is difficult because of the weak magnetization and high coercivity of hematite. We assess here the relative effectiveness of first‐order reversal curve (FORC) and extended FORC‐type diagrams, FORC‐principal component analysis (PCA), isothermal remanent magnetization (IRM) curve decomposition, and PCA of remanent hysteretic curves for unmixing magnetic components in samples from the magnetically complex Inuyama red chert, Japan. We also further characterize the domain state and coercivity distributions of both magnetite and hematite with FORC‐PCA and IRM acquisition analysis in the red chert. We show that IRM curve decomposition can provide valuable component‐specific information linked to coercivity, while FORC‐PCA enables effective magnetic domain state identification. PCA of remanent hysteretic curves provides useful information about the most significant factors influencing remanence variations and subtle coercivity changes. To identify components in complex magnetite and hematite mixtures, we recommend PCA analysis of remanent hysteretic curves combined with FORC analysis of representative samples to identify domain states and coercivity distributions.

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Analysis of hysteresis curves of samples with magnetite and hematite grains

Cited by 11 publications

References 2 publications

Wasp‐waisted hysteresis loops: Mineral magnetic characteristics and discrimination of components in mixed magnetic systems

Wasp‐waisted hysteresis loops: Mineral magnetic characteristics and discrimination of components in mixed magnetic systems

Mineral magnetic properties of mixtures of environmental and synthetic materials: linear additivity and interaction effects

Assessment of Magnetic Techniques for Understanding Complex Mixtures of Magnetite and Hematite: The Inuyama Red Chert

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