Core/shell SmCo5/Sm2O3 magnetic composite nanoparticles

Separated core/shell SmCo5/Sm2O3 composite magnetic nanoparticles have been fabricated by a mechanochemical process, heat treatment and washing in this study. Phases, microstructure, particle sizes, and magnetic properties of the as-synthesized SmCo5 and SmCo5/Sm2O3 nanoparticles and the influence of annealing temperature and time have been investigated. The results showed that the annealing temperatures had great effects on particle sizes and magnetic properties while annealing time had a little effect on the particle size of the annealed SmCo5 nanoparticles. The average particle sizes of the annealed SmCo5 nanoparticles changed from 176 to 362 nm when the annealing temperatures increased from 450 to 650 degrees C and annealing time was 1 h. The coercivity of the synthesized SmCo5 nanoparticles annealed at 450 degrees C for 1 h was 21 kOe. It increased with the increase of annealing temperatures and reached a maximum value of 35.5 kOe at 600 degrees C and then decreased. It is interesting to find that the core/shell SmCo5/Sm2O3 hard magnetic nanoparticles were formed after washing with ethanol and acetic acid aqueous solution. Magnetic measurements of these particles exhibited a higher coercivity of 23.7 kOe. The SmCo5 core reserves a single-crystal structure and a 68-75 nm size while the Sm2O3 has a thickness of 5 nm.