Nucleation and growth of magnetic domains in small RCo5particles

In order to investigate the magnetization process in hard-magnetic RCo
5
compounds (where R = Y, Ce, Pr and Sm), their magnetic domain structures were studied in the demagnetized state and in different magnetized states in an external magnetic field. The domains in small (10-100μm) RCo
5
particles were revealed using the magnetooptic Kerr technique. The observed domain structure is typical for a hexagonal material showing high crystalline anisotropy and having its direction of easy magnetization parallel to the
c
axis. Demagnetized particles even as small as 10 μm consist of a few domains. The demagnetization process of an initially fully magnetized particle thus proceeds by nucleation and subsequent growth of domains of reversed magnetization. We have observed the nucleation and growth of reverse domains in SmCo
5
and YCo
5
particles under the action of an external magnetic field.