Investigation of structure and magnetization reversal in mechanically alloyed SmCo6.8Zr0.2 magnets

Nanocrystalline SmCo6.8Zr0.2 permanent magnets are prepared by intensive milling and subsequent annealing. XRD patterns of the samples annealed at 600 degrees C and 700 degrees C show a single SmCo7 phase with TbCu7 structure, while the SmCo7 phase decomposes into a mixture of Sm2Co17 and Co23Zr6 phase at higher annealing temperatures. The highest coercivity and energy product of about 2.06 T and 9.5MGOe are obtained in the sample annealed at 700 degrees C for 10 min. Further analysis reveals that a very strong inter-grain exchange coupling is observed in samples annealed at 700 degrees C for 3 (SZ-3) and 10 (SZ-10) min, indicating by the high remanence ratio and positive delta m in henkel-plot. It was supposed that the magnetization reversal process is controlled by domain wall pinning. (C) 2011 Elsevier B. V. All rights reserved.