Effects of CoZrNb surface morphology on magnetic properties and grain isolation of CoCrPtO perpendicular recording media

In this paper, the sputtering pressure of the soft magnetic underlayers(SUL) was varied to study effects of SUL conditions such as surface morphology and residual stress on magnetic properties of the recording layers. As the sputtering pressure of the SUL increases, the coercivity (Hc) increases drastically up to 10 mtorr and decreases gradually beyond the pressure. TEM images reveal that the several grains of the CoCrPtO layer form a cluster and the cluster is surrounded by the thick oxides. The increased Hc is attributed to the reduction of exchange coupling among the clusters by making isolation through the thick oxide boundaries. The behavior of Hc variation with the sputtering pressure of the SULs is in good agreement with that of residual stress induced on the SUL. This is because the surface mophology is affected by the residual stress, and the grain isolation is very dependent on the surface topology of the SUL. However, the direct relationship between surface topology and residual stress is still not clearly known.