High-performance multiphase Sm-Co-B alloys with coercivities up to 6.71 MA·m−1

SmCo4B-based alloys with high magnetocrystalline anisotropy are expected to be used as raw materials or constituent phases for new permanent magnets. In this work, we develop Sm(Co, Fe, Ni)4B alloys with excellent hard magnetic properties by tuning the contents of Fe, Co, and Ni. The addition of Fe enhances the amorphous formation ability of the as-spun ribbons, whereas Ni addition improves the structural stability of the crystalline phases. During annealing, the amorphous phase crystallizes into different Sm-Co-B phases in stages. A high coercivity of 5.68–6.71 MA·m−1 is obtained in the annealed SmCo4–x–yFexNiyB (x = 1.0–2.0, y = 0.8–1.0) ribbons composed of platelet-shaped and equiaxed grains in comparison with the coercivity of 2.89–5.18 MA·m−1 in the x = 1.0–1.2 and y = 0–0.8 ribbons with equiaxed grains. Here, we show the strong correlations between the microstructure and magnetic properties and provide insights for the future development of high-performance SmCo4B-based magnets. Samarium Cobalt-based magnets are a vitally important industrial magnet, and significant effort has been devoted to trying to improve the performance and reduce the cost through the addition of Fe. Unfortunately, this comes at the expense of phase stability. Here, Wang et al show through careful choice of composition, a Samarium Cobalt permanent magnet with an ultrahigh coercivity of 6.71 MA/m.