Improved Coercivity in Cu-Doped SmCo5 Nanocomposite Powders Obtained by Low Temperature Annealing

Abstract

In this work, nanocrystalline SmCo₅–Cu nanocomposite powders were fabricated from the ball-milled amorphous matrix by crystallization annealing which is lower than the traditional sintering temperature ~ 1000 °C for bulk SmCo₅ bulk magnets. Annealed Cu-doped SmCo₅ powders have a higher coercivity compared to that of Cu-free SmCo₅ one due to the combined effects of refinement effect of grain size and the pinning effect induced by Cu doping. The peak of coercivity (H_c) is located at 600 °C for annealed Cu-doped SmCo₅, which is ascribed to the improved pinning field. The pinning effect became reduced when the annealing was done at even higher temperatures. More importantly, the best comprehensive magnetic properties, including a maximum magnetic energy product (BH)_max of 12.2 MGOe together with a coercivity of 31.8 kOe and a remanence of 64.3 emu/g, could be achieved for SmCo₅-3 wt% Cu by low temperature annealing. These results demonstrate that isotropic Cu-doped SmCo₅ nanocrystalline powders are promising precursors for the fabrication of high-performance bulk magnets.