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.