Microstructure of zinc-bonded Sm2Fe17N3 permanent magnet studied by transmission and analytical electron microscopy

Abstract

Microstructure of the Zn-bonded Sm2Fe17N3 permanent magnet having high magnetic coercivity of 11.8 kOe was studied by transmission and analytical electron microscopy. Three phases, α-Fe including 20 to 30 at%Zn, Fe3Zn7, and Sm2(Fe,Zn)17Nx, were found in addition to the matrix Sm2Fe17N3 phase. The Sm2(Fe, Zn)17Nx phase, in which a fraction 0.2 of Fe in Sm2Fe17N3 is replaced by Zn, surrounds the matrix grains and protects them from coming into contact with the α-Fe grains, which are considered to act as nucleation sites of reverse magnetic domains. It was concluded that the existence of the Sm2(Fe, Zn)17Nx phase causes the high coercivity.