Achievement of high coercivity in Sm(Fe0.8Co0.2)12 anisotropic magnetic thin film by boron doping

• Published in: Acta materialia Vol. 194; pp. 337 - 342
• Main Authors: Sepehri-Amin, H., Tamazawa, Y., Kambayashi, M., Saito, G., Takahashi, Y.K., Ogawa, D., Ohkubo, T., Hirosawa, S., Doi, M., Shima, T., Hono, K.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.08.2020
• Subjects: Coercivity; Higher performance permanent magnets; Nanostructured; Sm(Fe0.8Co0.2)12Bx; Thin magnetic film; ThMn12-type structure; Sm(Fe0.8Co0.2)12Bx; ThMn12-type structure; Nanostructured; Thin magnetic film; Coercivity; Higher performance permanent magnets
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2020.05.026

SmFe12-based compounds have been considered as promising candidates for next generation permanent magnet materials because of their excellent intrinsic hard magnetic properties with a minimum usage of rare earth elements. However, realizing high coercivity in anisotropic microstructure is a big challenge, which hinders their practical applications. In this work, a novel anisotropic granular microstructure of Sm(Fe0.8Co0.2)12 with a sufficiently large coercivity (µ0Hc) of 1.2 T and with a high remanent magnetization of 1.50 T is demonstrated in thin films prepared by co-sputtering Sm(Fe,Co)12 with boron. Detailed microstructure characterization using high resolution scanning transmission electron microscopy (STEM) and atom probe tomography (APT) indicate that the addition of B leads to the development of columnar-shaped Sm(Fe0.8Co0.2)12 grains with a size of ∼40 nm, which are surrounded by ∼3 nm-thick B-enriched amorphous intergranular phase. Domain wall pinning at the amorphous grain boundary phase is attributed to the high coercivity. This work provides a guiding principle for realizing high-coercivity anisotropic SmFe12-based permanent magnets, which can outperform Nd-Fe-B magnets and could be used as the next-generation high-performance permanent magnets in various applications. [Display omitted]