Physical and magnetic microstructure of rapid thermally annealed thin film bismuth-doped garnets

Abstract

Bismuth-doped iron garnets are promising materials for blue light magneto-optic recording media. These materials have been deposited on glass substrates with bulk magnetic and magneto-optic properties suitable for magneto-optic recording. However, these films exhibit a very low carrier to noise ratio (CNR) when crystallized in conventional furnaces. The low CNR is due to the inability to write circular domains in these materials. Rapid thermal annealing (RTA) has been reported to produce films with a much finer grain size. We have confirmed by transmission electron microscopy that RTA does indeed reduce the grain size over an order of magnitude from films crystallized in a conventional furnace. Faraday microscopy has shown that films processed by RTA with smaller grain size (∼30 nm) support circular magnetic domains of much greater regularity than films crystallized in conventional furnaces. The improved regularity of static thermomagnetically written domains, in films crystallized by RTA, lends promise that the noise in these materials can be reduced.