EFFECTS OF SPUTTERING CONDITIONS ON THE RECORDING CHARACTERISTICS OF IRON-OXIDE THIN-FILM MEDIA

Magnetite films (Fe3O4) were reactively sputtered onto (100) silicon substrates in an Ar + O2 gas environment from a target containing Fe and 0.75 at.% Os. The films were further oxidized in air to form γ-Fe2O3. The oxide thin-film disks were then written with a thin-film inductive head and read back with an experimental shielded MR element for recording performance evaluation. The medium noise increased with written transition density and reached a plateau at a linear density greater than 2000 flux changes per millimeter. This plateau, as well as the noise per transition at lower density, increased with substrate temperature but decreased with oxygen flow rate. The structural analysis of the films indicates that the medium noise improvement is a result of grain size reduction. However, films deposited at lower substrate temperatures exhibit degradation in B-H loop squareness, resulting in poor overwrite, peak jitter, peak shift, and -3 dB density. These and previous results indicate that a medium optimized with respect to both magnetic and mechanical properties is formed by depositing at a substrate temperature above 200°C and at an appropriate oxygen partial pressure.