Domain structure of exchange-coupled and exchange-decoupled Nd-Fe-B sintered magnets

摘要

Understanding the magnetization reversal processes in Nd-Fe-B sintered magnets is important in order to obtain a clue to enhance the coercivity of Nd-Fe-B magnets without using heavy rare earth elements. In order to meet the demand of high coercivity without changing the currently established powder metallurgy route, Nakajima and Yamazaki [K. Nakajima and T. Yamazaki, Japan Patent. (2015) 5767788] reported a new series of sintered magnets that achieve the coercivity of more than 1400 kA/m and the remanence of 1.38 T without refining the grain size. The microstructural characterization revealed well-isolated 2:14:1 grains with Ga-doped Nd-rich intergranular phase1. Such non-magnetic intergranular phase with the chemical composition Nd_6(Fe,Ga)_(14) was reported to decouple the ferromagnetic grains and reduce the influence of the reverse domain formation between neighboring grains. In this work, we observed the