Effects of Media Burnish Capability to Head-Disk Clearance

Abstract

As flying height is reduced to less than 10 nm, media morphology, overcoat, and lubricant start to have a significant effect in conditioning the head in the early stage of flying. Typical thermal pole tip protrusion (PTP) in the head writing process will further reduce the head-disk clearance and enhance the media burnishing effect on the trailing edge of the flying head. However, excessive burnishing could further damage the head. A properly designed media surface can burnish the head protrusion to maintain head-disk clearance. To observe the burnishing effects of the media surface, heads with a specially designed slider to increase head-disk interference during flying are used with an in-situ acoustic emission monitoring scheme to study the rate of head protrusion adjustment during proximity flying. Various surface textures, overcoat properties, and lubricant thickness are used to measure the media's burnishing power. It is found that surface microscopic features, especially in the circumferential direction, contribute significantly to the reduction of the media's burnishing power. A semi-analytical wear model and simulation are established to explain the texture effects. The overcoat hardness and lubricant coverage effects are also noted in the wear model and verified by experimental observation.