Effects of grain size and morphology on the coercivity of Sm2(Co1−xFex)17 based powders and spin cast ribbons

Abstract

The effects of grain/particle size and morphology on the coercivity of Sm2(Co1−xFex)17 based powders and spin cast ribbons are investigated in an attempt to make pure Sm–Co 2:17 magnets with a higher energy product than that currently available. It is observed that the coercive force is not only affected by the composition, but also significantly by the grain/particle size. The coercivity of the as-cast SmCo6 powder was increased from 0.5 to ∼12 kOe when the grain/particle size was decreased from 14 to 1.5 μm. A twofold increase in coercivity was also observed for some Sm(CO0.85Fe0.15)7.6 spin cast ribbons when the wheel speed was increased from 6 to 25 m/s and the grain size of the ribbons was decreased from 2–15 to 0.5–5 μm. The initial magnetization curves show a high degree of texture that exists in the free side of ribbons, with the c axis parallel to the longitudinal direction of the ribbons. The presence of a trace of boron in the ribbons changes the grain morphology and eliminates the texture. Some results show promise of making a high coercivity higher energy product Sm2(Co1−xFex)17 based magnets without adding nonmagnetic elements such as Cu and Zr.