Preparation of Sm−Fe−N Bulk Magnets with High Maximum Energy Products

• Published in: Journal of the Magnetics Society of Japan 2020/05/01, Vol.44(3), pp.64-69
• Main Authors: Matsunami, R., Matsuura, M., Tezuka, N., Sugimoto, S.
• Format: Article
• Language: English
• Subjects: Bonding; Coercivity; Density; fine Zn powder; low oxygen content; Magnetic properties; Magnetism; Magnets; maximum energy products; Oxygen; Oxygen content; Plasma sintering; Remanence; Sm−Fe−N magnets; Spark plasma sintering; Zinc; Zn binder
• ISSN: 1882-2924; 1882-2932
• DOI: 10.3379/msjmag.2005R003

In an effort to increase the maximum energy product ((BH)max) and coercivity (HcJ) of Zn-bonded Sm−Fe−N magnets, we developed a process for preparing Sm−Fe−N and Zn powders with low oxygen contents and subjected them to spark plasma sintering. The oxygen content, remanence, and coercivity of the Sm−Fe−N powder were 0.22 wt%, 151 A·m2·kg−1, and 0.72 MA·m−1, respectively. The oxygen content and secondary average particle size of the Zn powder were 0.083 wt% and 0.93 μm, respectively. The magnetic properties of the Zn-free Sm−Fe−N magnets included an HcJ of 0.86 MA·m−1 and a (BH)max of 188 kJ·m−3, while the Zn-bonded (10 wt%) Sm−Fe−N magnets exhibited excellent magnetic properties with a (BH)max of 200 kJ·m−3 and an HcJ of 1.28 MA·m−1. Compared with previous studies, this is the high (BH)max observed for a Sm−Fe−N bulk magnet simultaneously displaying a high HcJ. The (BH)max of the Zn-bonded magnets was greater than that of the Zn-free magnets owing to the higher relative density of the former. Therefore, Zn is an effective binder for increasing not only the coercivity but also the density of Sm−Fe−N magnets. Consequently, the procedure reported herein permits the successful preparation of high-performance Sm−Fe−N bulk magnets.