BA-FERRITE THIN-FILM MEDIA FOR HIGH-DENSITY LONGITUDINAL RECORDING

Ba-ferrite is an attractive candidate for future high-density recordin g media because of its large coercivity, corrosion resistance, high ha rdness, and durability. In contrast to most recent work on Ba-ferrite thin film media, polycrystalline films with large in-plane remanence f or longitudinal recording are emphasized. Films are prepared on a vari ety of substrates by on-axis sputtering at low temperatures from stoic hiometric targets followed by a postdeposition anneal in a rapid therm al processor at approximately 850-degrees-C to induce crystallization. Structural and chemical properties have been investigated by force mi croscopy, Rutherford backscattering, and other means. Stoichiometric f ilms have large 5000 angstrom grains that are unsuitable for high-dens ity recording. However, grain sizes as small as 200 angstrom have been produced by doping with small amounts of Cr2O3 and other additives. C ompositional changes also influence crystallite orientation. Exception al durability has been observed on disks without overcoats, presumably due to a fine-scale texturing that occurs during crystallization. Coe rcivities are greater than 4000 Oe even in small grain films. The effe ct of grain size on coercivity and signal-to-noise ratio of several Ba -ferrite disks is discussed. It is argued that the grains are magnetic ally decoupled based on the magnetic properties of these films.