Physical Properties of Bonded Nanocomposite Type Hard-Soft Magnets

The exchange spring magnetic powders of SmCo5/α-Fe were obtained by mechanical milling and annealing. SmCo5+20 wt% α-Fe powder milled for 8 h and annealed at about 550 °C was considered to be more appropriate for our purpose. The isotropic nanocomposite permanent magnets were obtained by bonding the magnet powder in a binder matrix. Several ratios from 0.5 to 1.5 wt % between binder and magnetic powder were used. The composite material was compacted in dies at pressure from 600 to 800 MPa. The heat treatments for polymerisation were performed at 180 °C for 1h. The density and the microstructure of the magnets are discussed in connection with the properties of the starting powder and processing conditions. Magnetic characteristics of Br, Hc and (BH)max were obtained from hysteresis curves in magnetic fields up to 10 T.