Microstructure and magnetic properties of bulk magnets Nd14–xFe76+xCo3Zr1B6 (x=0, 0.5, 1) prepared by spark plasma sintering

Melt-spun ribbons with nominal composition of Nd14–xFe76+xCo3Zr1B6 (x=0,0.5,1) were consolidated into isotropic bulk magnets by spark plasma sintering method. It was found that the Nd content and sintering temperature had significant influence on the density and magnetic properties of the sintered magnets. Homogeneous microstructure and fine grain (50–100 nm) were obtained when sintering below 700 °C, and the initial magnetization curve showed that the coercivity was controlled by the pinning mechanism. However, abnormally large grains and inhomogeneous microstructure in magnets were observed after sintering at 750 °C, furthermore, the grains were found to be multi-domain structure and the coercivity was mainly controlled by nucleation mechanism.