Overcoming coercivity-remanence trade-off via tuning the composition of ferromagnetic intergranular phase in Ga-doped Nd-Fe-B ribbons

The high-performance of a Nd-Fe-B magnet needs both large coercivity and remanence. However, the coercivity – remanence trade-off leads to a dilemma that the coercivity and the remanence cannot be simultaneously increased, and subsequently reduces the maximum energy product ((BH)max). Here, we use atom probe tomography (APT) and demonstrate a strategy that can simultaneously improve the coercivity (Hci) and the remanence (Br) by tuning the concentration of rare earths (Nd + Pr) and ferromagnetic elements (Fe + Co) of the ferromagnetic intergranular phase in (Nd0.1023Pr0.0256Fe0.6832Co0.1308B0.0581)99.7Ga0.3 melt-spun ribbons. In comparison to the Ga-free alloy, the Hci and the Br both increase to 1369 kA/m by 7.0% and to 0.85 T by 2.4%. Interestingly, the magnetic field annealing treatment (1 T, 623 K for 15 min) further improves the Br to 0.90 T with a minor decrease of the Hci. The (BH)max of 134 kJ/m3 is obtained, 12.6% higher than that of the 0.3 at% Ga-doped as-spun sample. Our findings provide an idea to overcome the coercivity-remanence trade-off and subsequently to design prospective permanent alloys with excellent magnetic properties by modifying the content of rare earths and ferromagnetic elements in the ferromagnetic intergranular phase.