Some aspects of the stability and anisotropy of amorphous Co-Gd films

Cobalt-gadolinium films were prepared by r.f. bias sputtering to produce films with compensation temperatures near room temperature corresponding to Co79Gd21. Kerr magneto-optic hysteresis loops measured at various temperatures were used to determine the compensation temperature. Torque curves indicated that these films had a perpendicular anisotropy. Rapid changes in the torque curves were measured as a function of time at room temperature on films with no protective overlay film. With about 1000Å SiO2over the film the compensation temperature and the torque characteristic were both stable to about 200°C for 2 hrs. At higher temperatures the compensation temperature decreased indicating an increase in cobalt in the film. This was confirmed by the increase in the torque component derived from the shape anisotropy of the disk while the component decreased. SIMS depth profiling could not confirm that this was due to oxidation or the release of argon. Transmission electron microscopy on a thinned cross-section of the film, and through film thickness, failed to reveal any structure other than equiaxed contrast with a wave length of about 20Å.