The most recent family of permanent magnets to be developed is SmFeN. This material is based on the Samarium-Iron-Nitride (Sm2Fe17N3) intermetallic compound and was discovered independently in the late 1980s by Michael Coey and Takahiko Iriyama. This compound possesses all the requirements for a permanent magnet including high saturation magnetization, a large magnetocrystalline anisotropy field, and a high Curie temperature. Since its discovery it has been considered a candidate for the eventual development of high performance permanent magnets comparable to Neodymium magnets. Nevertheless a fully dense SmFeN magnet has not yet been commercialized even though more than 25 years has elapsed since the discovery of the Sm2Fe17N3 intermetallic compound. This is because Sm2Fe17N3 is unstable above about 500 degrees Celsius, preventing the production of bulk magnets by either sintering or hot pressing of SmFeN powder. However, both compression and injection molded SmFeN magnets are now being produced.
Anisotropic bonded magnets with Sm2Fe17N3 powder and isotropic bonded magnets with SmFe9Nx powder have already been commercialized by several Japanese manufacturers. These magnets have the highest levels of magnetic properties of all bonded magnets. There is no deny that magnetic properties of a bonded magnet are limited by the magnetic properties of the magnetic powder. Therefore, the production process the SmFeN powder is most important to produce bonded SmFeN magnets. SmFeN powder is synthesized by nitrogenating the host SmFe powder. Anisotropic and isotropic SmFe host powders are produced by different methods; the former is made by melting-casting the SmFe alloy, or by reduction & diffusion (R/D) using Samarium Oxide and Iron powder as the starting materials; the latter is made by rapid quenching of the SmFe alloy. Frankly, Chinese SmFeN powder is still limited by production capacities and stability at present.