Xing-Cai Guo

Multidentate functionalized lubricant for ultralow head/disk spacing in a disk drive

As areal density in disk drive technology is marching towards the Tbit∕in.2 mark, the slider-to-disk spacing will be required to be within only a few nanometers. Coupled with very high slider velocities (>40m∕s), this leads to extremely high shear stresses on the nanometer-thin lubricant film at the disk surface. As a result, the lubricant film tends to exhibit local redistribution on a micrometer lateral level, decreasing the overall clearance and impacting the integrity of the interface. This paper describes a different approach to functionalized lubricant, where in addition to functional groups placed at the end of the chain, additional attachment moieties are introduced within the main polymer chain. The benefits of this approach is twofold: it increases adhesive interaction with the disk surface, therefore increasing the effective surface viscosity, while at the same time “tying” down the free backbone length for increased clearance. Fabrication, characterization, and performance data obtained on act...

Carbon Overcoat Oxidation in Heat-Assisted Magnetic Recording

Due to the ever increasing demand for higher storage capacity in disk drives, novel techniques to read and write information, such as heat-assisted magnetic recording are being developed. However, the recording temperatures impact not only the media but also the carbon overcoat that is used to protect both the media and writing head. In this paper, we discuss the effect of thermal annealing on the rate of carbon erosion on overcoats deposited using two different techniques, viz. filtered-cathodic arc and plasma-enhanced chemical vapor deposition.

A multidentate lubricant for use in hard disk drives at sub-nanometer thickness

We describe a second generation of multidentate lubricant structures for use on a magnetic media in a hard disk drive. Building on earlier work where a perfluoropolyether (PFPE) chain with hydroxyl bonding moieties were placed in the middle of the chain as well as on chain ends, creating a structure with two PFPE sub-units for enhanced tribological performance under very low head-disk spacing, this paper focuses on a PFPE chain composed of three, even shorter PFPE sub-units. Experimental data focusing on surface characterization of sub-nanometer thickness films, as well as tribological performance, are presented that confirm the high confinement level achieved with the lubricant structure. Molecular dynamics calculations are also discussed, that are consistent with a molecular film of high stiffness, leading to a denser, more compact structure. This approach could pave the way to achieving the sub-nanometer head-disk clearance level, presumed necessary for storage densities exceeding the terabit per squar...

Cobalt Oxalate Formation on Thin-Film Magnetic Recording Media

Needle-like crystalline nanostructures were formed on the surface of a lubricated experimental thin-film media during exposure to elevated temperature and humidity. Clusters of nodules were formed on unlubricated media during the same exposure. Both the needles and nodules were identified as cobalt oxalate by Micro-Raman spectroscopy. A chemical mechanism is proposed to explain how cobalt hydroxide corrosion product and atmospheric oxalic acid combine to form cobalt oxalate in the presence of moisture

Surface chemistry of NiP plated substrates

Circumferential texture grooves polished into NiP plated AlMg substrates promote magnetic crystal anisotropy in longitudinal recording media. Freshly textured or washed NiP is a chemically reactive surface, and combines with atmospheric moisture and carbon dioxide to form Ni carbonates. These adventitious products alter the surface morphology and interfere with magnetic domain growth.

Poisoning of orientation ratio on NiP-coated substrates

The surface chemical evolution of NiP-coated AlMag disk substrate was analyzed using contact angle, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy techniques. Its effect on magnetic film structure and orientation ratio was also studied. It was also shown that slow nickel carbonate surface growth under ambient condition poisoned the orientation ratio of the structure.