ABSTRACT

Development of high-performance permanent magnets relies on both the main-phase compound with superior intrinsic magnetic properties and the microstructure effect for the prevention of magnetization reversal. In this article, the microstructure effect is discussed by focusing on the interface between the main phase and an intergranular phase and on the intergranular phase itself. First, surfaces of main-phase grains are considered, where a general trend in the surface termination and its origin are discussed. Next, microstructure interfaces in SmFe₁₂-based magnets are discussed, where magnetic decoupling between SmFe₁₂ grains is found for the SmCu subphase. Finally, general insights into finite-temperature magnetism are discussed with emphasis on the feedback effect from magnetism-dependent phonons on magnetism, which is followed by explanations on atomic arrangements and magnetism of intergranular phases in Nd-Fe-B magnets. Both amorphous and candidate crystalline structures of Nd-Fe alloys are considered. The addition of Cu and Ga to Nd-Fe alloys is demonstrated to be effective in decreasing the Curie temperature of the intergranular phase.

摘要

高性能永磁体的开发依赖于具有优异固有磁性的主相化合物和防止磁化反转的微观结构效应。在本文中，通过关注主相和晶间相之间的界面以及晶间相本身来讨论微观结构效应。首先，考虑主相晶粒的表面，讨论表面终止的一般趋势及其起源。接下来，讨论了 SmFe ₁₂基磁体中的微结构界面，其中 SmFe _{12之间的磁去耦}在 SmCu 亚相中发现了晶粒。最后，讨论了对有限温度磁性的一般见解，重点讨论了磁性相关声子对磁性的反馈效应，然后解释了 Nd-Fe-B 磁体中的原子排列和晶间相的磁性。考虑了 Nd-Fe 合金的非晶结构和候选晶体结构。证明向 Nd-Fe 合金中添加 Cu 和 Ga 可有效降低晶间相的居里温度。