Studies on Magnetic Domains of Small Particles of Barium Ferrite by Colloid-SEM Method

Magnetic domains of barium ferrite particles less than 10 to 1 µm in size which are on surfaces of as-sintered blocks have been observed by colloid-SEM method, a modified Bitter method, with magnifications from 20000 to 45000. The number of domains in a particle decreases with reduction of particle size on average. Below about 2 µm in size each particle comprises two domains. It is shown that domain structure of the two-domain particle is plate-like, and the particle shape is found to be a double hexagonal pyramid with c -plane approximately. A single-domain particle 1.3 µm in size has been observed successfully. The possibility of the twisted domain wall in small multidomain particles is suggested from the obtained patterns of the magnetite powders.