Overcoat Free Magnetic Media for Lower Magnetic Spacing and Improved Tribological Properties for Higher Areal Densities

Abstract

Surface modification with shallow embedding (B1 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 (B1 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.

Enhanced Tribological, Corrosion, and Microstructural Properties of an Ultrathin (<2 nm) Silicon Nitride/Carbon Bilayer Overcoat for High Density Magnetic Storage

“…Apart from high sp 3 C content, high interfacial strength/bonding at the magnetic media–overcoat interface is also needed for enhanced tribological properties and wear protection. By controlling the C + ion energy using the FCVA technique, surface modification of the magnetic media had been performed to obtain an ultrathin graded protective overcoat (≤2.0 nm) by forming a mixed interfacial layer of carbon and media. , This graded overcoat structure was seen to improve the interfacial bonding between the COC and media, and exhibited a low coefficient of friction even without a lubricant layer. However, the overcoat fabricated by this FCVA surface modification technique has not been found to improve the corrosion performance over commercial hard disks …”

Ultrathin Si/C graded layer to improve tribological properties of Co magnetic films

“…3,4 Using the FCVA technique, surface modification methods have been developed to produce overcoat-free magnetic media with improved tribological performance. [5][6][7] This surface modification was achieved by bombarding the outermost layer of magnetic media with C þ ions at an ion energy of 90 eV to produce a mixed layer of Co or FePt and carbon in the top 1 nm of the magnetic media surfaces. This mixed layer exhibited excellent tribological properties in terms of reduced coefficient of friction as compared with the bare Co or FePt surface and the commercial HDD media.…”

The Head-Disk Interface Roadmap to an Areal Density of Tbit/in2

“…treated or modified without contributing to spacing loss with a creation of a nonfunctional or weakened layer of magnetic material on the media surface [48,49]. Table 2 shows that a 0.2 nm reduction of lubricant thickness from 1.0-1.2 to 0.8-1.0 is needed.…”

“…It remains to be seen whether conventional lubricant chemistries (functionalized perfluoropolyether) will be able to achieve this thickness goal. Perhaps unconventional approaches, such as direct surface treatment/functionalization of the disk overcoat will be needed [48].…”