Exchange interaction and demagnetization process of high-abundance rare-earth magnets sintered using dual alloy method

The 2:14:1-type rare-earth (RE)-Fe-B permanent magnets prepared by the dual alloy method have been found to possess much superior magnetic properties to those prepared by the single alloy method, providing an appealing route to promote the utilization of high-abundance RE elements Ce and La and balance the use of the RE source. However, the relationship between magnetic interactions among different 2:14:1 main phases and superior magnetic properties is still unclear. In this study, we investigated the magnetic interactions and reversal field distribution in these magnets using first-order reversal curve (FORC) images. The FORC images showed that (Nd, Pr)_27.8(La, Ce)_2.7Fe_balM_1.4B_1.0 (S-9) and (Nd, Pr)_19.5(La, Ce)_11.0Fe_balM_1.4B_1.0 (S-36) have the characteristics of multiple main phases. The reverse magnetic fields corresponding to the soft and hard main phases, as well as the associated exchange coupling, were highly dependent on the LaCe content. The higher the LaCe content, the weaker the exchange coupling and the more asynchronous the demagnetization process. In addition, the FORC images indicated that the magnetization reversal process also varies with LaCe content, where the nucleation and propagation of reversed domains dominant in the S-9 magnet, while the domain propagation in the S-36 magnet is considerably suppressed. Additional micro-magnetic simulations also revealed that the coercivity and exchange coupling of multi-main-phase magnets decrease with increasing LaCe content, correlating well with the experimental results. These findings may not only contribute to a better understanding of the complex magnetic interactions between the soft and hard phases and how they affect macroscopic magnetic properties but also help in improving the magnetic performance of the RE-Fe-B magnets with high LaCe content.