Rare-Earth Magnets

Livingston, J. D.

doi:10.1557/s0883769400035351

Cited by 8 publications

(4 citation statements)

References 15 publications

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“…In the same figure, eigenfrequencies predicted by the model are represented. An overall agreement is found between peaks of the transfer functions and theoretical eigenfrequencies with a relative error in the range [4][5][6][7][8][9][10][11][12][13][14][15] %. For the data plotted in fig.…”

supporting

confidence: 52%

“…-In the middle of the 1980's a new type of high energetic permanent magnet was developed [1,2], based on neodymium alloys (Nd 2 Fe 1 4B) designed by metallurgists [3]. Because of their strength and their small weight they enhanced the performances of many applications needing a magnetic field, like Magnetic Resonance Imagery [4], but also opened the possibility of a set of new applications in unexpected domain like medicine [5]. Because of their properties, the neodymium magnets can be used to build model experiments, where the magnets' collective behavior mimics those of microscopic systems (i.e.…”

mentioning

confidence: 99%

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Dynamics of a chain of permanent magnets

Boisson¹,

Rouby²,

Lee³

et al. 2015

EPL

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The dynamics of a straight chain of cylindrical neodymium magnets is considered. We showed this system exhibits a behavior which is similar to that of a beam where the elastic rigidity acts like a restoring force. By using a Lagrangian approach, a linear model, accounting for different sets of boundary conditions, is derived. Specifying to the clamped-free case eigenfrequencies and eigenmodes are determined. These theoretical results are compared to experiments. A good agreement is found, the discrepancies being attributed to the accumulation of defaults in the contact surface between the magnets. In the last part of the article, the equivalent beam behavior is sought for by defining an equivalent flexural rigidity induced by magnetic dipoles interactions.

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supporting

confidence: 52%

mentioning

confidence: 99%

Dynamics of a chain of permanent magnets

Boisson¹,

Rouby²,

Lee³

et al. 2015

EPL

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“…The magnets produced were sintered between 960 and 1100 • C. The sintering temperature was varied to get the optimum density (7.5-7.6 g cm −3 ) and (B H ) max . The density of the samples and the remanence increased with increasing sintering temperature, keeping the sintering time constant (3 h), while the squareness of the demagnetization curve only partly increased and drastically decreased when AGG of the Nd 2 Fe 14 B grains occurred [4]. AGG of the Nd 2 Fe 14 B grains occurred preferentially in magnets with low oxygen content.…”

Section: Nd 2 Fe 14 B Magnetsmentioning

confidence: 95%

“…The magnetic hardness of permanent magnet materials depends critically on the microstructure of the individual magnets. In the light of the historical development of the coercive field and the energy density product of hard magnetic materials the improvement of the energy density product is closely connected with a better understanding of the mechanisms leading to higher coercive forces of the magnets [1][2][3][4]. High external magnetic fields are necessary to obtain saturation in permanent magnets, unlike the case for soft magnetic materials, which are saturated by relatively low magnetic fields.…”

Section: Introductionmentioning

confidence: 99%

Recent developments in hard magnetic bulk materials

Fidler

Schrefl

Hoefinger

et al. 2004

J. Phys.: Condens. Matter

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The importance of newly developed permanent magnetic materials in many electromechanical, magnetomechanical and electronic applications is attributed to the drastic improvement in microstructure related properties, such as the remanence, the magnetic energy density product and the coercive field. The influence of the microstructure on the magnetic properties of the magnets will be discussed, where special emphasis is laid on rare earth permanent magnets. Highest performance, anisotropic Nd-Fe-B magnets with J r > 1.5 T, (B H) max > 450 kJ m −3 and J H c > 750 kA m −1 , which are produced by the powder metallurgy route, show a strong influence of composition and processing parameters on the magnetic properties. The magnetic properties of Sm(Co, Cu, Fe, Zr) z sintered magnets, which are used nowadays for high temperature applications between 300 and 500 • C, are determined by the cellular precipitation microstructure, which is developed during a complex heat treatment and by the microchemistry. Special hard magnetic powder materials, such as Sm 2 Fe 17 N 3 and nanocrystalline, composite Nd 2 Fe 14 B/(α-Fe, Fe 3 B) materials have been developed especially for usage in bonded magnetic materials, which show the strongest annual increase in the production of permanent magnets. The phenomenon of the enhancement of remanence, occurring in single phase and composite Nd 2 Fe 14 B based magnets with isotropic grain alignment, is attributed to intergrain exchange interactions.

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Rare‐earth Intermetallics for Permanent Magnet Applications

Fidler

Suess

Schrefl

2007

Handbook of Magnetism and Advanced Magnetic Materials

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Modern high‐performance permanent magnets are based on rare‐earth (RE) intermetallic compounds with excellent intrinsic magnetic properties as well as on optimized microstructures and alloy compositions. Outstanding hard magnetic properties such as energy density product and coercive field are obtained in binary and ternary RE (Sm, Nd, Pr) compounds with transition metals (TM = Co, Fe), in particular, based on RECo 5 and RE 2 Co 17 and RE 2 Fe 14 B. The complex microstructure considerably influences the magnetic reversal process. Intergranular phases change the coupling behavior between the hard magnetic grains. Nonmagnetic phases eliminate the direct exchange interaction and reduce the long‐range magnetostatic coupling. Both effects increase the coercive field in nucleation‐controlled magnets. The RE‐rich intergranular phase is necessary for the liquid phase sintering process, but deteriorates the corrosion stability and reduces the remanence. In order to improve coercive field, remanence and energy density, it is necessary to increase the volume fraction of the hard magnetic phase by reducing the amount of oxygen, nonmagnetic phases and pores, and to improve the degree of alignment of the hard grains. The difference in magnetic domain wall energy in precipitation hardened multiphase magnets determines the coercive field in domain wall pinning controlled magnets. The inhomogeneous magnetization behavior near the intergranular regions of nanocrystalline RE magnets, which is directly responsible for remanence and coercivity, is strongly influenced by the microstructural parameters. By using numerical micromagnetic simulations based on the finite element technique the correlation between microstructure and magnetic hysteresis properties can be quantitatively predicted, thus providing a powerful tool for the further development of optimized high‐performance Nd 2 Fe 14 B and Sm(Co,Cu) 5 /Sm 2 (Co,Fe) 17 ‐type magnets.

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Rare-Earth Magnets

Cited by 8 publications

References 15 publications

Dynamics of a chain of permanent magnets

Dynamics of a chain of permanent magnets

Recent developments in hard magnetic bulk materials

Rare‐earth Intermetallics for Permanent Magnet Applications

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