Magnetism of ultrathin intergranular boundary regions in Nd-Fe-B permanent magnets

Y. Murakami; T. Tanigaki; T. T. Sasaki; Y. Takeno; H. S. Park; T. Matsuda; T. Ohkubo; K. Hono; D. Shindo

doi:10.1016/j.actamat.2014.03.013

Magnetism of ultrathin intergranular boundary regions in Nd-Fe-B permanent magnets

Y. Murakami, T. Tanigaki, T. T. Sasaki, Y. Takeno, H. S. Park, T. Matsuda, T. Ohkubo, K. Hono, D. Shindo

Quantum Sciences of Materials

Research output: Contribution to journal › Article

63 Citations (Scopus)

Abstract

The magnetism of a thin grain-boundary (GB) phase that envelopes the Nd₂Fe₁₄B grains in optimally annealed Nd-Fe-B sintered magnets was investigated by electron holography. The phase shift measured from a thin-foil specimen containing a tilted amorphous GB phase (∼3 nm in width) was -0.34 rad, which is substantially smaller than that expected for the nonferromagnetic GB phase of -1.2 rad. Simulations of the phase shift with various magnetization values suggest that the magnetic flux density of the GB phase is ∼1.0 T. The observations imply significant exchange coupling between Nd₂Fe₁₄B grains, which can explain the avalanche propagation of magnetization reversal observed in sintered magnets.

Original language	English
Pages (from-to)	370-379
Number of pages	10
Journal	Acta Materialia
Volume	71
DOIs	https://doi.org/10.1016/j.actamat.2014.03.013
Publication status	Published - Jun 2014

All Science Journal Classification (ASJC) codes

Electronic, Optical and Magnetic Materials
Ceramics and Composites
Polymers and Plastics
Metals and Alloys

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Murakami, Y., Tanigaki, T., Sasaki, T. T., Takeno, Y., Park, H. S., Matsuda, T., Ohkubo, T., Hono, K., & Shindo, D. (2014). Magnetism of ultrathin intergranular boundary regions in Nd-Fe-B permanent magnets. Acta Materialia, 71, 370-379. https://doi.org/10.1016/j.actamat.2014.03.013

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title = "Magnetism of ultrathin intergranular boundary regions in Nd-Fe-B permanent magnets",

abstract = "The magnetism of a thin grain-boundary (GB) phase that envelopes the Nd2Fe14B grains in optimally annealed Nd-Fe-B sintered magnets was investigated by electron holography. The phase shift measured from a thin-foil specimen containing a tilted amorphous GB phase (∼3 nm in width) was -0.34 rad, which is substantially smaller than that expected for the nonferromagnetic GB phase of -1.2 rad. Simulations of the phase shift with various magnetization values suggest that the magnetic flux density of the GB phase is ∼1.0 T. The observations imply significant exchange coupling between Nd2Fe14B grains, which can explain the avalanche propagation of magnetization reversal observed in sintered magnets.",

author = "Y. Murakami and T. Tanigaki and Sasaki, {T. T.} and Y. Takeno and Park, {H. S.} and T. Matsuda and T. Ohkubo and K. Hono and D. Shindo",

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AU - Murakami, Y.

AU - Tanigaki, T.

AU - Sasaki, T. T.

AU - Takeno, Y.

AU - Park, H. S.

AU - Matsuda, T.

AU - Ohkubo, T.

AU - Hono, K.

AU - Shindo, D.

PY - 2014/6

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AB - The magnetism of a thin grain-boundary (GB) phase that envelopes the Nd2Fe14B grains in optimally annealed Nd-Fe-B sintered magnets was investigated by electron holography. The phase shift measured from a thin-foil specimen containing a tilted amorphous GB phase (∼3 nm in width) was -0.34 rad, which is substantially smaller than that expected for the nonferromagnetic GB phase of -1.2 rad. Simulations of the phase shift with various magnetization values suggest that the magnetic flux density of the GB phase is ∼1.0 T. The observations imply significant exchange coupling between Nd2Fe14B grains, which can explain the avalanche propagation of magnetization reversal observed in sintered magnets.

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