Jian-Ping Wang1

1, University of Minnesota, Minneapolis, Minnesota, United States

Rare-earth-free magnets are highly demanded by clean and renewable energy industries because of the supply constraints and environmental issues. A promising permanent magnet should possess a high remanent magnetic flux density (Br), a large coercivity (Hc), and consequently, a large energy product ((BH)max). BCT phase Fe16N2 has been emerging as one of the promising candidates because of its recently double-confirmed large magnetocrystalline anisotropy (Ku > 1.0x107 erg/cc), giant saturation magnetization (4πMs>2.4 T) and the enough availability of Fe and N on the earth. However, there is no report on the fabrication of bct phase Fe16N2 magnet with high Br and large Hc in bulk form yet. In this talk, I will report our group’s effort in recent ten years to prepare bct phase Fe16N2 permanent magnets by using different approaches, such as ion implantation method, ball milling method and strained-wire method, which can be looked as the dawn light of FeN rare-earth-free permanent magnet. At the beginning of my talk, I will review the mystery of Fe16N2 in our magnetic materials community, following by introducting our effort in past decade to clarify fundamental uncertaities related with this material, including 1) the discovery of the origin of the giant saturation magnetization of Fe16N2, 2) fabrication of partially ordered Fe16N2 samples with giant saturation magnetization; 3) finding of the local 3d electron states in Fe8N and Fe16N2; 4) finding of the role of Fe6-N octahedral clusters; 5) first-principle simulation based on a model of clusters (Fe6N) + atoms (Fe);