Role of Co on the magnetic properties of Ce-substituted Nd-Fe-B hot-deformed magnets

In this paper, we report for the first time improved hard magnetic properties of Ce-substituted Nd-Fe-B based anisotropic permanent magnet despite the expected reduction of intrinsic hard magnetic properties of (Nd_1-xCe_x)₂Fe₁₄B compound for x > 0. With increasing Ce substitution, x, from 0 to 0.1, the coercivity (μ₀H_c) increased from 1.36 T to 1.44 T while the remanent magnetization (J_r) remains to be 1.49 T when the magnets contain Co. Further increase in x decreases the remanent magnetization and coercivity. The ab initio calculations show that the magnetization would not be degraded if the Ce substitutes Nd at 4 g site in the Co-containing magnets, which is found to be the case by atom-resolved STEM-EDS mapping. The enhancement of coercivity of the sample with x = 0.1 originates from higher rare earth concentration in the grain boundary phase, resulting stronger pinning force against reversed domain wall motion. However, the improvement of hard magnetic properties with Ce substitution for Nd was not found in Co-free compounds.