Combustion assisted preparation of high coercivity Sm–Co hard magnet with stable single-domain size

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A surge of interest has in recent years focused on the preparation of size-controlled permanent magnets through chemical routes. Herein, a sol-gel combustion assisted reduction-diffusion process is used to synthesize Sm–Co particles with sizes within the stable single-domain (SSD) size range and resulting in an impressive high coercivity of 2176 kA m−1 (27.3 kOe) at 300 K and 4297 kA m−1 (54.0 kOe) at 10 K. The structure and size of Sm–Co particles can be tuned through the Co/Sm ratio in the precursor. The sample with an average particle size of 816 nm shows the best coercive force. Magnetic properties are highly dependent on the particle size. Recoil loops, Henkel plots, and δM plots proved the existing of interparticle exchange interactions, resulting high remanence/saturation (Mr/Ms) ratio. Spark Plasma Sintering (SPS) was used to directly compact the Sm–Co particles into bulk magnets. Hysteresis loops measured with the applied magnetic field parallel and perpendicular to the pressing direction revealed the SPS process to introduce strong magnetic anisotropy. Magnetic Force Microscopy (MFM) revealed the domain size to be close to pre-pressing average particle size, ensuring a respectable coercivity. The single-domain size combined with strong anisotropy results in a massive energy product of 182 kJ m−3 (22.9 MGOe).

OriginalsprogEngelsk
Artikelnummer152527
TidsskriftJournal of Alloys and Compounds
Vol/bind816
ISSN0925-8388
DOI
StatusUdgivet - 5 mar. 2020

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