# Fileset

[ISAMMA-2024_Sepehri-Amin.docx](https://mdr.nims.go.jp/filesets/e5c97e7b-fb5d-4e7a-baa2-3ccc2de18bb6/download)

## Creator

[SEPEHRI AMIN Hossein](https://orcid.org/0000-0002-7856-7897)

## Rights

[In Copyright](http://rightsstatements.org/vocab/InC/1.0/)

## Other metadata

[Design and development of permanent magnets;  how to solve rare-earth criticality while considering new demands?](https://mdr.nims.go.jp/datasets/38cdb8b7-47d8-4fd4-9b1a-badc452fd6c2)

## Fulltext

Design and development of permanent magnets; how to solve rare-earth criticality while considering new demands?H. Sepehri-Amin* 1National Institute for Materials Science, 1-2-1 Sengen, *h.sepehriamin@nims.go.jpPermanent magnets are widely used in green energy conversion and play an important role in achieving net-zero CO2 emissions. In order to maintain sustainable production of permanent magnets in the long term, it is necessary to eliminate the dependence of permanent magnets on critical elements such as Dy and to diversify the use of rare earths while maintaining their performance close to their theoretical limits. We will first present our fundamental research on why the coercivity of permanent magnets with different microstructural features are far below their theoretical limits (magnetic anisotropy field) (Figure 1). We will present several examples of how the combination of multiscale microstructure characterization and micromagnetic simulations paves the way for the design of high performance permanent magnets. This will be demonstrated for Dy-free Nd-Fe-B based permanent magnets, Nd-lean (Nd,Ce)-Fe-B magnets.  Furthermore, we will discuss the potential of SmFe12 based compounds and the current challenges to realize these materials as new permanent magnets [4-5].We will show our recent success in microstructure engineering of these materials, both in magnetic thin filmsd and in bulk magnetic materials, to realize sufficiently large coercivities above 1.0 T supported by machine learning [6]. Based on detailed microstructural characterizations, modeled thin films and micromagnetic simulations, the optimal microstructure that can lead to higher coercivity and remanent magnetization in the SmFe12-based magnets will be discussed. At the end of the talk we will discuss future strategies in the development of permanent magnets that need to be taken into account considering the emergence of new applications [2].Figure 1: Coercivity to magnetic anisotropy field ratio of different permanent magnets with different coercivity mechanism. General complex microstructure of different types of permanent magnets are shown, indicating the existence of different types of defects, secondary phases, and intergranular region [1-3]. References[1] E. P. Pan, K. Y. Lee, and M. X. Song, “Paper tile XXX…”, Appl. Phys. Lett. 50 (2023) 1354.image1.tiff