Single-layer and multilayered films for perpendicular recording based on a Co-Cr alloy

Results of materials research into the dependence of the magnetic properties of Co-Cr recording media on the structural properties are discussed in relation with results from recording experiments. The magnetic properties depend strongly on the preparation conditions. An increase in substrate temperature results in an increase of the coercivity, but also gives rise to inhomogeneities of the Co-Cr film in the growth direction and to lateral inhomogeneities due to Cr segregation. The inhomogeneities in the growth direction are suppressed by the application of a non-magnetic, amorphous Ge layer between the substrate and the Co-Cr layer, resulting in a magnetic layer with a large perpendicular anisotropy. From the slope of the hysteresis loops we obtain, using a model proposed by Kooy and Enz, an estimate for the mean size of the stripe domains, which is found to increase with increasing layer thickness and decrease with increasing substrate temperature. The change in the size of the stripe domains is consistent with the trends calculated from noise spectra obtained in recording experiments. Multilayers of thin Co-Cr layers alternated with non-magnetic Ge layers are also discussed.