Revisiting the Structural and Magnetic Properties of SmCo5/Sm2Co17 Interface from First-Principles Investigations

The formation and evolution of SmCo5/Sm2Co17 (1:5H/2:17R/H) cellular structures play an essential role in understanding the coercivity of Sm-Co magnets. Herein, the pristine and different elemental-doped 1:5/2:17R and 1:5/2:17H interfaces are investigated to evaluate the elemental site preferences, interface configurations, and magnetic properties in Sm2Co17-type magnets with general alloy elements M (M = Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Al, Si, and Ga). Comparing the calculated results of 1:5/2:17H with those of the 1:5/2:17R interface, we found that Cu and Mn always segregate at the 1:5 phase, and Ga elements first appear at the 1:5 phase in 1:5/2:17H and then change to the 2:17 phase in 1:5/2:17R. While Ti, V, Fe, Zn, Al, and Si elements always tend to segregate at the 2:17 phase, Ni first segregates at the 2:17 phase in 1:5/2:17H and then occupies the 1:5 phase of 1:5/2:17R. The 1:5/2:17H interface along the c-axis expands about 1.98~3.28%, while the 1:5/2:17R interface slightly shrinks about 0.04~0.87% after element doping. This suggests that different interface stress behaviors exist for high-temperature and room-temperature phase Sm2Co17-type magnets. Furthermore, Mn, Fe, and Ga doping improved the saturation magnetization strength. Our results provide new insights into understanding the effect of elemental doping at the interfaces of 1:5H/2:17R cellular structures.