Predicting fly-height modulation and contact forces in ultra-low flying head-disk interfaces using a tri-state switching dynamic contact model

摘要

In order to achieve higher recording densities up to 1 Tbit/In{sup}2 using conventional recording technologies, the recording slider will need to "fly" within 5 nm or less from the rotating disk. In such ultra-low flying height regimes, intermittent head/disk contact is unavoidable. Head/disk contact can cause large vibrations of the recording slider in the normal and lateral (off-track) directions as well as damage the disk due to large dynamic contact forces. This paper describes a simple continuum mechanics-based model that includes the dynamics of a flying head/disk interface (HDI) as well as the contact dynamics. Specifically, a lumped parameter one degree-of-freedom, three state nonlinear dynamic model representing the normal dynamics of the HDI and an asperity-based contact mode] are developed. The effects of realistic (dynamic microwaviness) and harmonic input excitations, contact stiffness (surface roughness) and air-bearing force during contact on fly-height modulation (FHM) and contact force are investigated. Based on the tri-state model predictions, design guidelines for reduced FHM and dynamic contact force are suggested.