Magnetic properties of small particles for possible magneto-optical pigments

Some peculiarities in the magnetic properties of ferrite small particles that may influence their magneto-optical performance are discussed. Particles with the rare-earth iron garnet (RIG) structure and with the hexagonal barium-ferrite structure are emphasized. The presence of a noncollinear spin structure in the surface of a particle and its variation with the temperature as well as a possible reduction in the exchange interactions in the core of a particle in the RIG small ferrimagnetic particles provide a basis for some of the peculiarities observed in the macroscopic magnetic properties. There is a surface effect and possibly also a process-induced bulk effect; as a result the Faraday rotation in these particles may be reduced. A minimization of the process-induced magnetic properties by improving the fabrication process, especially for the RIG small particles, and/or the construction of new media with process-insensitive materials would seem to be keys for the further development of these particles as MO pigments