Micrometer-size Nd-Fe-B dots as model systems for the study of intergranular phase engineering in Nd-Fe-B permanent magnets

Roy, Damien; Akdoğan, Ozan; Ciuta, Georgeta; Dempsey, Nora; Givord, D.

doi:10.1063/1.4867128

Cited by 5 publications

(1 citation statement)

References 9 publications

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“…The mechanism of coercivity is an enduring topic of magnetism, [17,[29][30][31][32][33][34][35][36][37][38][39][40][41][42][43] which is especially true because a permanent magnet characterized by a high coercivity is considered. The Stoner-Wohlfarth model (SW model) [44] is the most promising time-independent model to date.…”

Section: Coherent Rotation and Domain Wall Motionmentioning

confidence: 99%

Coercivity mechanisms in nanostructured permanent magnets*

Zhao¹,

Zhao²,

Shen³

et al. 2019

Chinese Phys. B

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Coercivity mechanism in permanent magnets has been debated for many years. In this paper, various models of the coercivity mechanism are classified and re-examined by the comparison and contrast. Coherent rotation and curling models can reveal the underlying reversal mechanism clearly based on isolated grains with elliptic shapes. By contrast, the numerical methods consider inter-grain interactions while simulating the evolution of the spins and hysteresis loops with complicated shapes. However, an exact simulation of magnetic reversal in permanent nanomagnets requires many meshes to mimic the thin domain wall well. Nucleation and pinning are the two main coercivity mechanisms in permanent magnets. The former signifies the beginning of the magnetic reversal, whilst the latter completes it. Recently, it is proposed that the large difference between the intrinsic magnetic properties of the nucleation centers and those of the main phase can result in a large pinning field (self-pinning), which has the attributes of both traditional nucleation and pinning. Such a pinning explains the experimental data of permanent magnets very well, including the enhancement of the coercivity by the grain boundary pinning.

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Section: Coherent Rotation and Domain Wall Motionmentioning

confidence: 99%

Coercivity mechanisms in nanostructured permanent magnets*

Zhao¹,

Zhao²,

Shen³

et al. 2019

Chinese Phys. B

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Replacement and Original Magnet Engineering Options (ROMEOs): A European Seventh Framework Project to Develop Advanced Permanent Magnets Without, or with Reduced Use of, Critical Raw Materials

McGuiness

Akdoğan

Asali

et al. 2015

JOM

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Characterization of the magnetic properties of NdFeB thick films exposed to elevated temperatures

et al. 2018

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Hard magnetic films used in magnetic micro-systems may be exposed to elevated temperatures during film and system fabrication and also during use of the micro-system. In this work, we studied the influence of temperature on the magnetic properties of 10 μm thick out-of-plane textured NdFeB films fabricated by high rate triode sputtering. Out-of-plane hysteresis loops were measured in the range 300K – 650K to establish the temperature dependence of coercivity, magnetization at 7 T and remanent magnetization. Thermal demagnetization was measured and magnetization losses were recorded from 350K in films heated under zero or low (-0.1 T) external field and from 325 K for films heated under an external field of -0.5 T. The effect of thermal cycling under zero field on the remanent magnetization was also studied and it was found that cycling between room temperature and 323 K did not lead to any significant loss in remanence at room temperature, while a 4% drop is recorded when the sample is cycled between RT and 343K. Measurement of hysteresis loops at room temperature following exposure to elevated temperatures reveals that while remanent magnetisation is practically recovered in all cases, irreversible losses in coercivity occur (6.7 % following heating to 650K, and 1.3 % following heating to 343K). The relevance of these results is discussed in terms of system fabrication and use.

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Micrometer-size Nd-Fe-B dots as model systems for the study of intergranular phase engineering in Nd-Fe-B permanent magnets

Abstract: International audienc

Cited by 5 publications

References 9 publications

Coercivity mechanisms in nanostructured permanent magnets*

Coercivity mechanisms in nanostructured permanent magnets*

Replacement and Original Magnet Engineering Options (ROMEOs): A European Seventh Framework Project to Develop Advanced Permanent Magnets Without, or with Reduced Use of, Critical Raw Materials

Characterization of the magnetic properties of NdFeB thick films exposed to elevated temperatures

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