Multiscale simulations toward understanding effects of amorphous grain boundary on coercivity in Nd-Fe-B magnets

• Applicant: Professorin Dr.-Ing. Bai-Xiang Xu, since 4/2019
• Subject Area: Thermodynamics and Kinetics as well as Properties of Phases and Microstructure of Materials ; Glass, Ceramics and Derived Composites ; Synthesis and Properties of Functional Materials
• Term: from 2018 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 409656180

In Nd-Fe-B magnets which are essential for modern energy-related technologies, the thin amorphous grain boundary (AGB) phase surrounding Nd2Fe14B grains is confirmed to notably affect the coercivity. But the underlying mechanism is not yet fully understood. The structural diversity and nanoscale feature of Nd2Fe14B/AGB interface make understanding AGB effects on coercivity challenging. Coercivity in Nd-Fe-B magnets relies on not only the local properties at the electronic and atomic level in the Nd2Fe14B/AGB interface vicinity, but also the magnetic reversal at both the atomic and microscopic levels. In this project, we will perform multiscale simulations by integrating first principles, atomistic spin model, and micromagnetics, toward a multilevel understanding of the AGB effects on the coercivity in Nd-Fe-B magnets. The Nd2Fe14B/AGB structure will be generated by an ab initio MD scheme combined with an evolutionary algorithm. Then atomic-resolved magnetic properties (atomic magnetic moment, atomic MAE of Fe, crystal field parameters of Nd ions, and atomic-pair exchange parameters) in the vicinity of Nd2Fe14B/AGB interface with/without additional elements will be calculated from first principles. With them as input, the atomistic spin model will be parameterized and numerically implemented to reveal the atomic-scale magnetic reversal. Finally, the combined atomistic spin and micromagnetic simulations will be applied to understand the AGB effects on coercivity in the multigrain cases. Atomistic spin model will be used to link with micromagnetic simulations by calculating interfacial region atomistically while treating the bulk region with a micromagnetic discretization. This project should disclose the multiscale picture of the magnetic reversal and coercivity mechanism in Nd2Fe14B/AGB systems, and inspire an atomic-scale engineering of local magnetic properties.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Dr. Min Yi, until 4/2019