Magnetic domain structures of precipitation-hardened SmCo 2:17-type sintered magnets: Heat treatment effect

The typical magnetic domains of Sm(CobalFe0.25Cu0.07Zr0.02)7.4 magnets quenched through various heat-treatment steps have been revealed by using magnetic force microscopy (MFM). For the specimens in which the nominal c-axis is perpendicular to the imaging plane, the domain configurations change from plate-like for the as-sintered magnet to corrugation and spike-like for the homogenized one, and then to a coarse and finally to a finer domain structure when isothermally aged at 830°C and then annealed at 400°C. However, only plate-like domains can be detected on the surfaces with the nominal c-axis parallel to the imaging plane. The finer domain (so-called interaction domain) is a characteristic magnetic domain pattern of the Sm–Co 2:17-type magnets with high coercivities. Domain walls in a zigzag shape are revealed by means of MFM in final bulk Sm–Co 2:17-type sintered magnets.