The origin of graduated demagnetization curves of NdFeB magnets

Heisz, S.; Hilscher, G.

doi:10.1016/0304-8853(87)90714-1

Cited by 23 publications

(5 citation statements)

References 11 publications

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“…This resultantly alters the magnetic properties of the samples. Another reason may be the oxidation of soft magnetic layers in the presence of atmospheric oxygen [38]. This type of behavior arises due to a mixture of grain boundaries and combination of magnetic composites possessing different magnetic properties [39].…”

Section: Resultsmentioning

confidence: 99%

Temperature-Dependent Magnetic Response of Antiferromagnetic Doping in Cobalt Ferrite Nanostructures

Nairan

Khan

et al. 2016

Nanomaterials

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In this work MnxCo1−xFe2O4 nanoparticles (NPs) were synthesized using a chemical co-precipitation method. Phase purity and structural analyses of synthesized NPs were performed by X-ray diffractometer (XRD). Transmission electron microscopy (TEM) reveals the presence of highly crystalline and narrowly-dispersed NPs with average diameter of 14 nm. The Fourier transform infrared (FTIR) spectrum was measured in the range of 400–4000 cm−1 which confirmed the formation of vibrational frequency bands associated with the entire spinel structure. Temperature-dependent magnetic properties in anti-ferromagnet (AFM) and ferromagnet (FM) structure were investigated with the aid of a physical property measurement system (PPMS). It was observed that magnetic interactions between the AFM (Mn) and FM (CoFe2O4) material arise below the Neel temperature of the dopant. Furthermore, hysteresis response was clearly pronounced for the enhancement in magnetic parameters by varying temperature towards absolute zero. It is shown that magnetic properties have been tuned as a function of temperature and an externally-applied field.

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Section: Resultsmentioning

confidence: 99%

Temperature-Dependent Magnetic Response of Antiferromagnetic Doping in Cobalt Ferrite Nanostructures

Nairan

Khan

et al. 2016

Nanomaterials

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“…The most striking feature of [13] is the predicted "knee" in the force-power curve, which occurs when ␥ 2 T 1 T 2 B 1 2 ϳ 1. Physically, the knee occurs when the RF power is sufficient to saturate the magnetization of the resonant slice at z ϭ 0.…”

Section: The Steady-state Solutionmentioning

confidence: 97%

“…both temperatures is dominated by the B 1 2 -term in the numerator in Eq. [13], and consequently we expect the lower portion of the normalized curves to overlap. Above the knee, the curves agree within our estimated errors, which seems to indicate that the unknown saturation mechanism which governs the upper slope is not strongly temperature-dependent.…”

Section: Description Of the Datamentioning

confidence: 97%

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The Bloch Equations in High-Gradient Magnetic Resonance Force Microscopy: Theory and Experiment

Dougherty¹,

Bruland²,

Chao³

et al. 2000

Journal of Magnetic Resonance

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“…A significant amount of work has been done on materials that display wasp-waisted hysteresis loops in the permanent rare earth magnet induslxy because constriction of the hysteresis curve drastically reduces the maximum energy produced by a magnet. Heisz and Hilscher [1987] reviewed three explanations for the origin of this type of behavior, including: (1) superposition of hard and soft magnetic phases, (2) oxidation of the surface layers of a magnetically soft material, and (3) spin reorientation which results in changes in the magnetic structure below 135 K. The first two of these mechanisms are applicable in the temperature ranges encountered in geological contexts and are therefore pertinent to the discussion outlined in this paper.…”

confidence: 99%

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

Roberts¹,

Cui²,

Verosub³

1995

J. Geophys. Res.

533

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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The origin of graduated demagnetization curves of NdFeB magnets

Cited by 23 publications

References 11 publications

Temperature-Dependent Magnetic Response of Antiferromagnetic Doping in Cobalt Ferrite Nanostructures

Temperature-Dependent Magnetic Response of Antiferromagnetic Doping in Cobalt Ferrite Nanostructures

The Bloch Equations in High-Gradient Magnetic Resonance Force Microscopy: Theory and Experiment

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

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