Linear stability analysis of gas-lubricated slider in magnetic recording system with ultra-thin spacing

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Abstract
The dynamics of a magnetic head flying above a rotating disk with a flying height of the order of one sub-micron or less are discussed. The generalized gas molecular lubrication equation, with roughness and rarefaction effects taken into account, and the equations of motion of the magnetic head are solved simultaneously in the linear stability regime. As the coefficients of the dynamic system are time varying, the nonlinear algebraic equation for the characteristic frequency in the Laplace transform domain is solved iteratively. The stability boundaries are obtained for various roughness parameters (Peklenik number, , and standard deviations of composite roughness height, ) and operating parameters (modified bearing number, ). It is shown that there exists a critical bearing number for a certain moment of inertia/mass ratio of the slider. It is also shown that the slider can fly at a lower height and is more stable when either transversely oriented roughness or a low disk velocity is utilized. A design procedure for stable head-disk operating conditions is also proposed.