Pr-Fe and Nd-Fe-based materials: A new class of high-performance permanent magnets (invited)

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Abstract
We report the properties of a new class of high‐performance permanent magnets prepared from Nd‐Fe‐B and Pr‐Fe‐B alloys. Magnetic hardening is achieved by rapid solidification. Energy products of these isotropic materials can exceed 14 MGOe with intrinsic coercivities of ∼15 kOe. X‐ray and microstructural analyses indicate that the alloys exhibiting optimum characteristics are comprised of roughly spherical crystallites, strongly suggesting that the coercivity mechanism is of the single‐domain particle type. The crystallites are composed of an equilibrium R‐Fe‐B intermetallic phase having tetragonal symmetry, and the stability of this phase with respect to other rare earths and other metalloids has been investigated.