J. S. Jiang
美国Argonne国家实验室
报告时间：3月10日（周一）下午4:00
报告地点：唐仲英楼A213会议室
摘要：
The exchange-spring mechanism, in which a soft magnetic phase is hardened via interfacial exchange coupling to a hard magnetic phase and enhances the total magnetization, is a possible solution for reducing or eliminating the expensive rare earth elements that are currently necessary in the production of high-performance permanent magnet materials. The properties of exchange-spring magnets are intimately connected with the material characteristics at the nano-scale. The development of the optimal exchange-spring permanent magnet benefits from a rational design of the nanostructure that balances exchange hardening, magnetization enhancement, and the feasibility of scalable fabrication.
I will give an overview of our investigations of the fundamental magnetization processes in exchange-spring magnets using multilayered model experimental systems. The model systems were designed and were controlled during synthesis via epitaxial thin-film growth. We have demonstrated that an exchange-spring magnet with an already-ideal interface can be further improved by creating a graded interface. We have also assessed the potential of various exchange-spring geometries for maximizing the energy density (BH)max. By analyzing the magnetization processes with both micromagnetic simulations and nucleation theory, we have identified that the geometry with cylindrical soft inclusions in a hard matrix is optimal. Such a structure permits the soft phase to be relatively large, does not require strict size control, and may be amenable to scaled-up fabrication.
Work supported by UChicago Argonne, LLC, operator of Argonne National Laboratory, a U.S. Department of Energy Office of Science laboratory, operated under contract No. DE-AC02-06CH11357.