Grain boundary diffusion in nanocrystalline Nd-Fe-B permanent magnets with low-melting eutectics

Sawatzki, Simon; Kübel, Christian; Ener, Semih; Gutfleisch, Oliver

doi:10.1016/j.actamat.2016.05.048

Cited by 78 publications

(20 citation statements)

References 44 publications

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“…Microstructure engineering has been explored to design high-coercivity Nd-Fe-B magnets, e.g. optimizing the grain shape and reducing the grain size to decrease the local effective demagnetization factor N eff [10][11][12][13][14], doping Nd 2 Fe 14 B grain or its surface with Dy or Tb to increase the anisotropy field H A [15][16][17][18], deceasing M s of GB to make Nd 2 Fe 14 B grains exchange decoupled by GB diffusion [19][20][21], etc. Based on the micromagnetic theory, the coercivity of Nd-Fe-B magnets can be tailored by controlling the distribution of three parameters, i.e.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic exchange in Nd–Fe–B permanent magnets

Gong

Evans

Gutfleisch

et al. 2019

Materials Research Letters

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The exchange is critical for designing high-performance Nd-Fe-B permanent magnets. Here we demonstrate through multiscale simulations that the exchange in Nd-Fe-B magnets, including bulk exchange stiffness (A e) in Nd 2 Fe 14 B phase and interface exchange coupling strength (J int) between Nd 2 Fe 14 B and grain boundary (GB), is strongly anisotropic. A e is larger along crystallographic a/b axis than along c axis. Even when the GB Fe x Nd 1−x has the same composition, J int for (100) interface is much higher than that for (001) interface. The discovered anisotropic exchange is shown to have profound influence on the coercivity. These findings enable more freedom in designing Nd-Fe-B magnets by tuning exchange. IMPACT STATEMENT Bulk exchange stiffness in Nd 2 Fe 14 B and interface exchange coupling strength between Nd 2 Fe 14 B and grain boundary are found strongly anisotropic, which have profound influence on the coercivity of Nd-Fe-B magnets.

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Section: Introductionmentioning

confidence: 99%

Anisotropic exchange in Nd–Fe–B permanent magnets

Gong

Evans

Gutfleisch

et al. 2019

Materials Research Letters

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“…An impressive example of the sustainable handling of REEs is the "grain boundary diffusion process" concept [17,18] used to decrease the proportion of dysprosium in NdFeB magnets. These magnets are mixed with dysprosium so that they are heat resistant, for instance, for use in wind power plants.…”

Section: Introductionmentioning

confidence: 99%

<i>Shaping the future with Rare Earth Elements</i> – Model Experiments for “damage monitoring” with [Eu(DBM)<SUB>4</SUB>TEA] and for Recycling of Neodymium(III) Sulfate from Hard Disk Magnets

Prechtl¹,

Schmidt²

2019

WJCE

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Rare Earth Elements (REEs: Sc, Y, La-Lu) are found in numerous future-oriented applications such as in magnets for green technologies and in fluorescing materials. A shortage of resources is already forecast for diverse REEs, which suggests it may be necessary to recycle these elements and optimize technologies. Both aspects will be addressed in this paper. Model experiments with regards to damage monitoring using [Eu(DBM) 4 TEA] and the recycling of neodymium(III) sulfate in hard disk magnets will also be presented. These are experiments for teachers and students who already have advanced experimental experience, such as trainees at vocational schools.

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“…The difficulty lies in the facts that nucleation sites are too small to be characterized and that one can hardly discern which clusters can effectively serve as nucleation sites. But from another point of view, crystallites precipitate out on nucleation sites at the very beginning of crystallization with the formation of nanovoids at grain boundaries 19 . Positron annihilation lifetime spectroscopy (PALS) is an efficient method to provide precise information about characteristic positron annihilation sites in nanocrystalline alloys, such as interstitial holes, vacancies and grain boundaries 20,21 .…”

Section: Introductionmentioning

confidence: 99%

Local structure, nucleation sites and crystallization behavior and their effects on magnetic properties of Fe81Si x B10P8−xCu1 (x = 0~8)

Cao

Wang

Zhu

et al. 2018

Sci Rep

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In this work, an attempt has been made to reveal critical factors dominating the crystallization and soft magnetic properties of Fe81SixB10P8−xCu1 (x = 0, 2, 4, 6 and 8) alloys. Both melt spun and annealed alloys are characterized by differential scanning calorimetry, X-ray diffractometry, Mössbauer spectroscopy, transmission electron microscopy, positron annihilation lifetime spectroscopy and magnetometry. The changes in magnetic interaction between Fe atoms and chemical homogeneity can well explain the variation of magnetic properties of Fe81SixB10P8−xCu1 amorphous alloys. The density of nucleation sites in the amorphous precursors decreases in the substitution of P by Si. Meanwhile, the precipitated nanograins gradually coarsen, but the inhibiting effect of P on grain growth diminishes causing the increase of the crystallinity. Moreover, various site occupancies of Si are observed in the nanocrystallites and the Si occupancy in bcc Fe decreases the average magnetic moment of nanograins. Without sacrificing amorphous forming ability, we can obtain FeSiBPCu nanocrystalline alloy with excellent soft magnetic properties by optimizing the content of Si and P in the amorphous precursors.

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Grain boundary diffusion in nanocrystalline Nd-Fe-B permanent magnets with low-melting eutectics

Cited by 78 publications

References 44 publications

Anisotropic exchange in Nd–Fe–B permanent magnets

Anisotropic exchange in Nd–Fe–B permanent magnets

<i>Shaping the future with Rare Earth Elements</i> – Model Experiments for “damage monitoring” with [Eu(DBM)<SUB>4</SUB>TEA] and for Recycling of Neodymium(III) Sulfate from Hard Disk Magnets

Local structure, nucleation sites and crystallization behavior and their effects on magnetic properties of Fe81Si x B10P8−xCu1 (x = 0~8)

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