Microstructure Origin of the Large Coercivity in an (Nd, Dy)-Fe-B Sintered Magnet

17 Pages Posted: 7 Sep 2022

See all articles by Xin Tang

Xin Tang

National Institute for Materials Science - Elements Strategy Initiative Center for Magnetic Materials (ESICMM)

J. Li

National Institute for Materials Science - Elements Strategy Initiative Center for Magnetic Materials (ESICMM)

Hossein Sepehri-Amin

National Institute for Materials Science - Elements Strategy Initiative Center for Magnetic Materials

Anton Bolyachkin

National Institute for Materials Science - Elements Strategy Initiative Center for Magnetic Materials (ESICMM)

A. Martin-Cid

Japan Synchrotron Radiation Research Institute

S. Kobayashi

Japan Synchrotron Radiation Research Institute

Yoshinori Kotani

Japan Synchrotron Radiation Research Institute

M. Suzuki

Japan Synchrotron Radiation Research Institute

A. Terasawa

Research Organization for Information Science and Technology

Y. Gohda

Tokyo Institute of Technology

Tadakatsu Ohkubo

National Institute for Materials Science - Elements Strategy Initiative Center for Magnetic Materials (ESICMM)

Tetsuya Nakamura

Japan Synchrotron Radiation Research Institute

Kazuhiro Hono

National Institute for Materials Science - Elements Strategy Initiative Center for Magnetic Materials (ESICMM)

Abstract

(Nd,Dy)-Fe-B sintered magnets are the crucial components for elevated temperature applications in the energy sectors. However, lack of understanding on their magnetic hardening mechanism hinders the development of high-performance Dy-lean Nd-Fe-B magnets. Conventional understandings on the origin of high coercivities (Hc) in the (Nd,Dy)-Fe-B sintered magnets have stressed on the intrinsic aspects, namely the large anisotropy field (HA) of (Nd,Dy)2Fe14B compounds, while overlooking the microstructural contributions. Herein, we unveil the extrinsic origins of the large coercivities in (Nd,Dy)–Fe-B sintered magnets. Detailed characterizations on the microstructure and the magnetism of grain boundary (GB) phase reveal that 4 at.% Dy in the intergranular phase reduces its magnetization, contributing to the large coercivity of 3.32 T. This leads to a change of hardening mechanism from the pinning-type Kondorsky model for the Dy-free magnet to the nucleation-dominated Stoner-Wohlfarth model for the Dy-containing magnet. Consequently, an exceptionally large value of 40 % for Hc/HA is realized for (Nd,Dy)–Fe-B sintered magnet, two times larger than that for the Dy-free magnet. Our findings highlight that Dy in the intergranular phase plays a critical role for achieving high coercivity. This can be exploited as a strategy for microstructure engineering toward the development of Dy-lean high-performance permanent magnets.

Keywords: Permanent magnets, coercivity, (Nd, Dy)-Fe-B, magnetism of grain boundary phase, hardening mechanism

Suggested Citation

Tang, Xin and Li, J. and Sepehri-Amin, Hossein and Bolyachkin, Anton and Martin-Cid, A. and Kobayashi, S. and Kotani, Yoshinori and Suzuki, M. and Terasawa, A. and Gohda, Y. and Ohkubo, Tadakatsu and Nakamura, Tetsuya and Hono, Kazuhiro, Microstructure Origin of the Large Coercivity in an (Nd, Dy)-Fe-B Sintered Magnet. Available at SSRN: https://ssrn.com/abstract=4212209 or http://dx.doi.org/10.2139/ssrn.4212209

Xin Tang (Contact Author)

National Institute for Materials Science - Elements Strategy Initiative Center for Magnetic Materials (ESICMM) ( email )

Tsukuba
Japan

J. Li

National Institute for Materials Science - Elements Strategy Initiative Center for Magnetic Materials (ESICMM) ( email )

Hossein Sepehri-Amin

National Institute for Materials Science - Elements Strategy Initiative Center for Magnetic Materials ( email )

Tsukuba
Japan

Anton Bolyachkin

National Institute for Materials Science - Elements Strategy Initiative Center for Magnetic Materials (ESICMM) ( email )

Tsukuba
Japan

A. Martin-Cid

Japan Synchrotron Radiation Research Institute ( email )

Japan

S. Kobayashi

Japan Synchrotron Radiation Research Institute ( email )

Japan

Yoshinori Kotani

Japan Synchrotron Radiation Research Institute ( email )

Japan

M. Suzuki

Japan Synchrotron Radiation Research Institute ( email )

Japan

A. Terasawa

Research Organization for Information Science and Technology ( email )

Y. Gohda

Tokyo Institute of Technology ( email )

2-12-1 O-okayama, Meguro-ku
Tokyo 152-8550, 52-8552
Japan

Tadakatsu Ohkubo

National Institute for Materials Science - Elements Strategy Initiative Center for Magnetic Materials (ESICMM) ( email )

Tsukuba
Japan

Tetsuya Nakamura

Japan Synchrotron Radiation Research Institute ( email )

Japan

Kazuhiro Hono

National Institute for Materials Science - Elements Strategy Initiative Center for Magnetic Materials (ESICMM)

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