Overcoat free magnetic media for lower magnetic spacing and improved tribological properties for higher areal densities

Surface modification with shallow embedding (≤1 nm) of carbon in the top layer of magnetic media is evaluated for its tribological and anti-oxidation properties. Cobalt is used as the magnetic material and carbon embedding is achieved by using the filtered cathodic vacuum arc technique at different ion energies, specifically of 20, 90, and 350 eV, in order to study the effect of ion energy on the embedding profiles. Simulations using the transport of ions in Matter software and X-ray photoelectron spectroscopy (XPS) are used to characterize the embedded layer and their surface chemical composition. XPS and transmission electron microscopy depth profiling results confirm the presence of a shallow mixed layer of carbon and cobalt for all three types of ion energies tested. However, embedding carried out at the ion energy of 90 eV produced a more uniform overcoat free mixed layer (≤1 nm) with improved anti-oxidation properties. Ball-ondisk wear tests and atomic force microscopy based scratch tests are conducted on the bare cobalt and modified cobalt surfaces. It is observed that the wear life and scratch resistance of the cobalt surface improved considerably after surface modification at the ion energy of 90 eV.