Observation on single-domain particles of Sm2Co7 compound

Magnetic domain patterns obtained on the polished surfaces of particles are shown for fine Sm2Co7 single-phase particles (high-temperature phase, hexagonal). As the particle diameter increases, the number of domains within the particle decreases. Measurements of the particle diameter distribution were performed for 485 single-domain particles. From these data, the critical diameter for the single-domain particles on the polished surfaces is 3.8 μm and the critical diameter for spherical particles is 5.5 μm. From the measured saturation magnetization of 636 G and the critical diameter, a domain-wall energy density of 150 erg/cm2 is obtained. Samples with sizes of 5.5 μm, oriented in the matrix, had a maximum coercivity of 13.2 kOe.