First-principles determination of intergranular atomic arrangements and magnetic properties in rare-earth permanent magnets

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.

Automated summary

This article discusses the microstructure effect on the development of high-performance permanent magnets, focusing on the interface between the main phase and intergranular phase, as well as the finite-temperature magnetism. Insights into the surface termination of main-phase grains and magnetic decoupling in SmFe12-based magnets are provided, along with discussions on atomic arrangements and magnetic properties of intergranular phases in Nd-Fe-B magnets. Additional elements like Cu and Ga are shown to decrease the Curie temperature of the intergranular phase.