Microstructure optimization to achieve high coercivity in anisotropic Nd-Fe-B thin films

W. B. Cui; Y. K. Takahashi; K. Hono

doi:10.1016/j.actamat.2011.09.006

Microstructure optimization to achieve high coercivity in anisotropic Nd-Fe-B thin films

W. B. Cui, Y. K. Takahashi, K. Hono^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

95 Citations (Scopus)

Abstract

A high coercivity of 2.35 MA m^-1 (29.5 kOe) is demonstrated using perpendicular anisotropy Nd-Fe-B films. Single layer columnar grown Nd-Fe-B thin films with a coercivity comparable with that of sintered magnets (1.11 MA m^-1, 14.0 kOe) were used as the starting film. The coercivity was doubled by annealing films capped with Nd, Nd/Cu, and Nd/Ag layers. Transmission electron microscopy indicated that the Nd ₂Fe₁₄B columnar grains were isolated by a Nd-rich grain boundary phase formed by diffusion of the capped layers into the grain boundaries of the polycrystalline Nd-Fe-B films. The temperature dependence of coercivity was lower than that of commercial sintered magnets. The coercivity of the Nd/Cu diffusion processed sample at 473 K was 0.979 MA m^-1 (12.3 kOe), which is higher than that of Nd₁₀Dy₄Fe ₈₀B₆ sintered magnets.

Original language	English
Pages (from-to)	7768-7775
Number of pages	8
Journal	Acta Materialia
Volume	59
Issue number	20
DOIs	https://doi.org/10.1016/j.actamat.2011.09.006
Publication status	Published - 2011 Dec
Externally published	Yes

Keywords

Coercivity
Nd-Fe-B thin films
Permanent magnets
Transmission electron microscopy

ASJC Scopus subject areas

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

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10.1016/j.actamat.2011.09.006

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title = "Microstructure optimization to achieve high coercivity in anisotropic Nd-Fe-B thin films",

abstract = "A high coercivity of 2.35 MA m-1 (29.5 kOe) is demonstrated using perpendicular anisotropy Nd-Fe-B films. Single layer columnar grown Nd-Fe-B thin films with a coercivity comparable with that of sintered magnets (1.11 MA m-1, 14.0 kOe) were used as the starting film. The coercivity was doubled by annealing films capped with Nd, Nd/Cu, and Nd/Ag layers. Transmission electron microscopy indicated that the Nd 2Fe14B columnar grains were isolated by a Nd-rich grain boundary phase formed by diffusion of the capped layers into the grain boundaries of the polycrystalline Nd-Fe-B films. The temperature dependence of coercivity was lower than that of commercial sintered magnets. The coercivity of the Nd/Cu diffusion processed sample at 473 K was 0.979 MA m-1 (12.3 kOe), which is higher than that of Nd10Dy4Fe 80B6 sintered magnets.",

keywords = "Coercivity, Nd-Fe-B thin films, Permanent magnets, Transmission electron microscopy",

author = "Cui, {W. B.} and Takahashi, {Y. K.} and K. Hono",

note = "Funding Information: This work was supported by NEDO through the Rare Metal Substitute Materials Development Project on the “Development of technology for reducing dysprosium usage in a rare-earth magnet” and Toyota Motor Co. Ltd.",

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doi = "10.1016/j.actamat.2011.09.006",

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AU - Cui, W. B.

AU - Takahashi, Y. K.

AU - Hono, K.

N1 - Funding Information: This work was supported by NEDO through the Rare Metal Substitute Materials Development Project on the “Development of technology for reducing dysprosium usage in a rare-earth magnet” and Toyota Motor Co. Ltd.

PY - 2011/12

Y1 - 2011/12

N2 - A high coercivity of 2.35 MA m-1 (29.5 kOe) is demonstrated using perpendicular anisotropy Nd-Fe-B films. Single layer columnar grown Nd-Fe-B thin films with a coercivity comparable with that of sintered magnets (1.11 MA m-1, 14.0 kOe) were used as the starting film. The coercivity was doubled by annealing films capped with Nd, Nd/Cu, and Nd/Ag layers. Transmission electron microscopy indicated that the Nd 2Fe14B columnar grains were isolated by a Nd-rich grain boundary phase formed by diffusion of the capped layers into the grain boundaries of the polycrystalline Nd-Fe-B films. The temperature dependence of coercivity was lower than that of commercial sintered magnets. The coercivity of the Nd/Cu diffusion processed sample at 473 K was 0.979 MA m-1 (12.3 kOe), which is higher than that of Nd10Dy4Fe 80B6 sintered magnets.

AB - A high coercivity of 2.35 MA m-1 (29.5 kOe) is demonstrated using perpendicular anisotropy Nd-Fe-B films. Single layer columnar grown Nd-Fe-B thin films with a coercivity comparable with that of sintered magnets (1.11 MA m-1, 14.0 kOe) were used as the starting film. The coercivity was doubled by annealing films capped with Nd, Nd/Cu, and Nd/Ag layers. Transmission electron microscopy indicated that the Nd 2Fe14B columnar grains were isolated by a Nd-rich grain boundary phase formed by diffusion of the capped layers into the grain boundaries of the polycrystalline Nd-Fe-B films. The temperature dependence of coercivity was lower than that of commercial sintered magnets. The coercivity of the Nd/Cu diffusion processed sample at 473 K was 0.979 MA m-1 (12.3 kOe), which is higher than that of Nd10Dy4Fe 80B6 sintered magnets.

KW - Coercivity

KW - Nd-Fe-B thin films

KW - Permanent magnets

KW - Transmission electron microscopy

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Microstructure optimization to achieve high coercivity in anisotropic Nd-Fe-B thin films

Abstract

Keywords

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