Strategy for high-coercivity Nd–Fe–B magnets

The formation of continuous thin layers of a Nd-rich amorphous phase surrounding Nd2Fe14B grains is the key microstructural feature of high-coercivity Nd–Fe–B magnets. Contrary to popular belief, a quantitative 3D atom probe investigation suggests that the thin grain boundary phase is ferromagnetic in both sintered and hydrogen disproportionation desorption recombination magnets. Model experiments using Nd–Fe–B thin films indicate that the intrinsic coercivity of μ0Hc = 3 T with improved temperature dependence is achievable by magnetically isolating Nd2Fe14B grains of ∼100 nm.