Cellular structure regulation and coercivity enhancement induced by La2O3 doping in 2:17 type SmCo magnet

The nanoscal cellular structure and coercivity was effectively regulated by doping La2O3 in Sm(Co0.79Fe0.09Cu0.90Zr0.03)7.68 magnet. The coercivity was gradually enhanced from 20.24 kOe to 24.18 kOe with doping content increasing. The evolution of the microstructure and magnetization reversal behavior were investigated. It was found that short-range Th2Zn17 type 2:17R microtwins structure appeared in the vicinity of (La, Sm)2O3 phase after solution treatment in addition to well-ordered Th2Ni17 type 2:17H phase. After aging treatment, the cellular structure nearby the (La, Sm)2O3 phase tend to grow into larger size, while the other cellular structure remain the same size with that in magnet without doping. More importantly, higher Cu content and lower Fe content was observed in the cell boundary phase nearby the oxide than that away from the oxide. The movement of domain wall under applied magnetic field indicated that the pinning field nearby the (La, Sm)2O3 phase was strengthened, which led to the increase of coercivity. Interesting, large enhancement of coercivity was observed in 2:17 type SmCo magnet by La2O3 doping according to the demagnetization curves. The movement of domain wall under applied magnetic field characterized by LTEM shows that the pinning field nearby the oxide phase was strengthened greatly. [Display omitted] •The phase constitution and nanoscal cellular structure was effectively regulated by doping La2O3.•The Th2Zn17 type 2:17R microtwins could be stabilized during the aging treatment in the vicinity of (La, Sm)2O3 phase.•The 2:17R microtwins structure as well as the lamellar phase which act as the diffusion path for Cu segregation.•The pinning field nearby the (La, Sm)2O3 phase was strengthened.