SmFeN Magnets

SmFeN represents the latest family of permanent magnets developed to date. It is founded on the Samarium-Iron-Nitride (Sm₂Fe₁₇N₃) intermetallic compound, independently discovered in the late 1980s by Michael Coey and Takahiko Iriyama. The compound meets all essential criteria for a permanent magnet, such as elevated saturation magnetization, substantial magnetocrystalline anisotropy field, and a high Curie temperature.

From the time of its discovery, it has been viewed as a promising option for creating high performance permanent magnets on par with Neodymium magnets. Nonetheless, a fully dense SmFeN magnet remains uncommercialized, despite over 35 years passing since the identification of the Sm₂Fe₁₇N₃ intermetallic compound. The reason lies in Sm₂Fe₁₇N₃‘s instability beyond approximately 500 degrees Celsius, which hinders bulk magnet fabrication through sintering or hot pressing of SmFeN powder. That said, compression-molded and injection-molded SmFeN magnets are currently in production.

Several Japanese producers have already brought to market anisotropic bonded magnets using Sm₂Fe₁₇N₃ powder and isotropic bonded magnets using SmFe₉N_x powder. These stand out with the superior magnetic properties among all bonded magnets. Undeniably, the magnetic characteristics of a bonded magnet are constrained by those of its constituent powder. Thus, the manufacturing process for SmFeN powder is crucial in creating bonded SmFeN magnets. SmFeN powder is created through the nitrogenation of precursor SmFe powder. Anisotropic and isotropic SmFe precursor powders are generated via distinct techniques: the anisotropic version through melt-casting the SmFe alloy or reduction-diffusion (R/D) starting from samarium oxide and iron powder; the isotropic version via rapid quenching of the SmFe alloy. To be candid, Chinese SmFeN powder production continues to face constraints in capacity and consistency today.

Magnetic Properties of Injection Molded SmFeN Magnets

Material	Grade	Remanence Br		Coercivity Hcb		Intrinsic Coercivity Hcj		Max. Energy Product (BH)max		Temperature Coefficient %/℃		Density ρ	Flexural Strength
Material	Grade	T	kGs	kA/m	kOe	kA/m	kOe	kJ/m³	MGOe	α (Br)	β (Hcj)	g/cm³	MPa
SmFeN/Ferrite Hybrid Magnet	30A	0.37	3.70	213	2.67	336	4.22	25.5	3.20	-0.13	-0.35	3.61	98
	40A	0.45	4.50	220	2.76	398	5.00	32.4	4.07	-0.09	-0.48	3.70	91
	50A	0.48	4.80	270	3.39	423	5.32	40.6	5.10	-0.08	-0.48	3.79	89
SmFeN Magnet	60A	0.52	5.20	349	4.39	576	7.23	50.3	6.32	-0.07	-0.48	3.62	92
	70A	0.57	5.70	363	4.57	554	6.96	57.9	7.27	-0.08	-0.48	3.88	91
	80A	0.60	6.00	371	4.66	525	6.60	64.7	8.13	-0.08	-0.48	4.11	91
	90A	0.64	6.40	400	5.02	550	6.91	75.2	9.45	-0.08	-0.48	4.33	88
SmFeN/NdFeB Hybrid Magnet	100A	0.69	6.90	408	5.12	701	8.81	82.0	10.30	-0.10	-0.57	4.45	99
SmFeN/NdFeB Hybrid Magnet	120A	0.78	7.80	454	5.70	812	10.20	99.3	12.47	-0.10	-0.57	4.95	91
The above-mentioned data of magnetic properties and physical properties are given at room temperature. The max working temperature of magnet is changeable due to length-diameter ratio and other environment factors.