It is observed a turning point in the particle size for which the coercivity Hci of a Sm-Co alloy reaches a peak. Using a broad size range from 20 nm to 5 mm, the turning point of the flake thickness for SmCo5 nanoflakes is determined in the range of 100–180 nm with Hci peak at ∼20 kOe. A lower coercivity at a particle size well below the turning point is likely related to a more detailed nanoscale morphology that controls coercivity. The effect of particle size on crystallinity for high energy milled powder is also discussed with four observations.
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