Effects of machining on magnetic properties of Nd-Fe-B system sintered magnets

Nishio, Hiroaki; Yamamoto, Hiroshi; Nagakura, Mitsuru; Uehara, Minoru

doi:10.1109/20.50550

Cited by 29 publications

(5 citation statements)

References 8 publications

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“…[23], and they are marked with black squares. The decrease in polarization at the right side of the curves was caused by the demagnetization of the areas at the surface that exhibited a strongly reduced coercivity compared to those of the bulk type [24][25][26]. In Figure 3, the magnetic viscosity parameter S v , which is dependent on the internal magnetic field, is shown for the selected temperatures.…”

Section: Resultsmentioning

confidence: 99%

“…The respective positions for the demagnetizing field

were determined in accordance with [ 23 ], and they are marked with black squares. The decrease in polarization at the right side of the curves was caused by the demagnetization of the areas at the surface that exhibited a strongly reduced coercivity compared to those of the bulk type [ 24 , 25 , 26 ].…”

Section: Figurementioning

confidence: 99%

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The Field-Dependent Magnetic Viscosity of FeNdB Permanent Magnets

Kresse,

Martinek,

Schneider

et al. 2024

Materials

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The time-dependent decrease of the magnetic polarization of magnet materials in the presence of an opposing field is well known as the magnetic viscosity or magnetic aftereffect. In previous studies, magnetic viscosity was usually measured in fields when in the vicinity of coercivity HcJ, and this was conducted in order to understand the coercivity mechanism in magnetic materials. In this study, the magnetic viscosity of commercial FeNdB magnets is determined at opposing fields weaker than HcJ and at different temperatures in the range from 303 to 433 K (i.e., from 30 to 160 °C) by means of a vibrating sample magnetometer (VSM). As a result, the parameter Sv, which describes the magnetic viscosity in the material, was found to increase with increases in the opposing field. Furthermore, both the parameter Sv and its dependence on the temperature were found to correlate with the coercivity HcJ of the material. Also, a difference with regard to the parameter Sv for the materials measured in this study with similar magnetic properties, but which had undergone different types of processing, could not be found. Knowledge of the field- and temperature-dependent behavior of the magnetic viscosity of FeNdB magnets allows for better estimations over the lifetime of a component under operating conditions with respect to the magnetic losses in FeNdB magnets that are used in electric components.

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Section: Resultsmentioning

confidence: 99%

“…The respective positions for the demagnetizing field

Section: Figurementioning

confidence: 99%

The Field-Dependent Magnetic Viscosity of FeNdB Permanent Magnets

Kresse,

Martinek,

Schneider

et al. 2024

Materials

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show abstract

“…For the material itself, N55 has a nonlinear B–H curve in the 2nd quadrant, while N48SH and SmCo30 have linear B–H curves in the 2nd and even in part of the 3rd quadrant. SmCo30 was tested so that the surface degradation can be excluded, which may be more obvious for some small or thin Nd–Fe–B magnets 9 .…”

Section: Experiments Methodsmentioning

confidence: 99%

Revealing the mystery of the cases where Nd–Fe–B magnetic like poles attract each other

Meng¹,

Tang²,

Shen³

et al. 2021

Sci Rep

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This investigation reveals the mystery of the cases where magnetic like poles attract each other, and unlike poles repel one another. It is identified that for two unequally sized like poles, the pole with a higher Pc (permeance coefficient) causes a localized demagnetization (LD) to the pole with a lower Pc. If the LD is large enough, the polarity of a localized area can be reversed, resulting in an attraction between these two like poles in the LD area in a small gap. Two unusual behaviors are observed: (1) an inflection point IP appears on the force vs gap curves of all the unequally sized like poles since they have different Pc. Normally, the like poles’ repelling force increases when the gap decreases, but this IP results in nonmonotonic curves, even an attractive force in a small gap; (2) for some NdFeB magnets with a low coercivity and nonlinear B–H curve in the 2nd quadrant, a repulsion can occur for these unequal sized unlike poles, after previously pairing with their like poles that left an unrecoverable LD and reversed polarity area. The relationship of the LD, the Pc ratio, and the B–H curve are also explored in this paper.

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“…Subsequently, the magnetization distribution before cutting was estimated using the magnetic simulation software JMAG 31) to compensate for the demagnetizing field due to the shape change. 8) In this method, the main factor of the evaluation uncertainty was the sample volume. Because the accuracy of the cutting process was approximately ±1 vol%, the evaluation uncertainty of the magnetization was also deduced to be ±10%.…”

Section: Destructive Inspection Methodsmentioning

confidence: 99%

“…6,7) The smaller the cutting size of the magnet, the worse the deterioration. 8) Therefore, a nondestructive measurement method is required to measure the magnetization distribution inside a magnet with a high accuracy and spatial resolution.…”

Section: Introductionmentioning

confidence: 99%

High-spatial-resolution measurement of magnetization distribution using polarized neutron imaging

Sasada¹,

Hiroi²,

Osanai³

et al. 2021

Jpn. J. Appl. Phys.

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The evaluation of the magnetization distribution inside a bulk magnet is important for ensuring the performance of automotive motors because it strongly depends on the quality of magnetization inside the permanent magnet. In the conventional destructive method, it is difficult to accurately measure the magnetization with a high spatial resolution. The polarized neutron imaging technique can be used to visualize the distribution of the magnetic flux density inside a magnet nondestructively. In this study, we demonstrated the imaging of the magnetization distribution using polarized neutrons in an anisotropic ferrite magnet sample. The 2D distribution of the magnetization was experimentally obtained by polarized neutron imaging with a high spatial resolution of less than 1 mm. Furthermore, the validity of the results was confirmed by comparing them with those obtained using the conventional destructive method.

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Effects of machining on magnetic properties of Nd-Fe-B system sintered magnets

Cited by 29 publications

References 8 publications

The Field-Dependent Magnetic Viscosity of FeNdB Permanent Magnets

The Field-Dependent Magnetic Viscosity of FeNdB Permanent Magnets

Revealing the mystery of the cases where Nd–Fe–B magnetic like poles attract each other

High-spatial-resolution measurement of magnetization distribution using polarized neutron imaging

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