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Ever decreasing magnetic spacing in the hard disk drive requires each contribution to the magnetic spacing to be examined for possible reduction. Currently, the lubricant layer on top of the disk carbon overcoat is typically 10-20 Å thick. This paper studies the contact resistance of nonlubricated disks with the aim of seeking a way to reduce the lubricant thickness contribution to the magnetic spacing. We prepared normally lubricated (thickness >; 7 Å), partially lubricated (thickness 3.5 Å), and barely lubricated (thickness 0.5 Å) disks. Partially lubricated disks showed contact wear resistance as good as normally lubricated disks when they were baked in a dry oven. We suggest that this enhanced contact wear resistance comes from the softening (graphitization) of the carbon overcoat and/or reduced number of active sites on the overcoat for water adsorption due to oxidation during the baking. However, corrosion resistance of partially lubricated disks became worse after baking and the amount of lubricant transfer from partially lubricated disk to slider surface did not decrease compared to normally lubricated disks. Barely lubricated disks showed very bad contact wear resistance even after baking, showing that it is necessary to have at least partial lubrication on the disk surface.
Date of Publication: Jan. 2011