Tohoku University Technology: Rare-earth free ferromagnetic particle powder showing BHmaxabove 6 MGOe: T19-390_T19-706_T19-709

Realization of α"-Fe16N2particle powder with giant saturation magnetization

The international market price of neodymium has increased significantly in recent years. The reason seems to be the increasing demand for windpower generation and electric vehicle motor in China where the country is promoting decarbonization as a national policy. In addition, the perspective of economic security is discussed in Japan and there is a strong demand for magnetic material which does not contain rare earth. Low cost Fe-N magnetic material consisting only of iron and nitrogen has especially high expectation. In particular, α"-Fe16N2 which has BCT structure and predicted to have high magnetic saturation, has attracted much attention. 　However, α"-Fe16N2 is a metastable compound that crystallizes when Fe-N compound is annealed, and there is almost no report of its isolation as a bulk material. The only few reported cases mention about eutectic crystal of α"-Fe16N2 and stable phase, or the existence for only 10 days at 100°C, so there is no example of α"-Fe16N2 single phase stable isolation as a bulk. 　This invention is about the α"-Fe16N2 stable isolated powder. This magnetic powder shows a BHmax of more than 6 MGOe (48 kJ/m3), which is higher than ferrite and alnico. It also shows the saturation magnetization of 221 emu/g which exceeds metallic Fe, and the coercivity of more than 2 kOe (160 kA/m) which is higher than alnico and comparable to ferrite. Since this magnetic powder can produce magnet that outperforms ferrite and alnico without using rare earth, it is expected to be used in motor, etc. as an alternative to neodymium magnet which continues to rise in price.

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