申请人前期研究发现，当RE-Fe-B磁体中存在不同La、Ce含量的多个主相时，各主相之间存在显著的交换耦合，导致富La、Ce的多主相磁体性能远超直接添加La、Ce的单主相磁体。在此基础上，本项目研究多主相(La,Ce,Nd)-Fe-B磁体内秉特性和宏观磁性能随La、Ce替代量和主相成分设计的变化，研究主相间交换耦合的作用规律。通过理论模拟和实验测试，研究La、Ce替代量和主相成分对主相内秉磁性和结构稳定性的影响。观察分析磁体组织结构、成分分布和磁畴结构的变化规律，尤其是相邻主相和主相/晶界相的界面成分分布、组织结构和磁畴结构，探索主相间交换耦合作用机理。通过优化关键工艺，强化交换耦合作用，制备La、Ce替代量较大的高性能高丰度稀土永磁。本项目将深化对RE-Fe-B磁体的理论认识，促进我国稀土资源高效和平衡利用，降低稀土永磁生产成本，具有重要的理论意义和广阔的应用前景。

Applicants have found that in La/Ce-rich RE-Fe-B magnets there were significant exchange coupling interactions between different main phases when there were over one main phases with different contents of La and Ce. It results in superior magnetic properties of multiple main phase magnets to those of single main phase magnets in which La and Ce were directly added in. On this basis, the change of intrinsic characteristics and magnetic properties of (La,Ce,Nd)-Fe-B magnets with multiple main phases is investigated in this project. The principle for exchange coupling interactions of different main phases is explored. Through theoretical simulation and experimental measurement, the effects of La, Ce addition and composition design of main phases on the intrinsic characteristics and structural stabilities are studied. The microstructure, distribution of chemical compositions, and the distribution of magnetic domains of magnets are observed and analyzed, particularly for interfaces between adjacent main phases and main phases/intergranular phases. The mechanism responsible for the exchange coupling interactions of different main phases is laid emphasis and explored in detail to prepare high performance La/Ce-rich magnets. The project will deepen the theoretical understanding of RE-Fe-B magnets, prepare rare earth permanent magnets with high La and Ce contents and low cost, and promote effective and balanced utilization of rare earth resources in China. Therefore, the project is of great theoretical significance and broad application prospects.