Investigation of contact stiffness and contact damping for magnetic storage head-disk interfaces

As the areal density of magnetic disk storage continues to increase and head-disk spacing decreases, contact between the recording slider and the rotating media becomes imminent. In order to predict contact forces, fly-height modulations, and off-track motions, dynamic models are typically used. A critical element of these models is the contact stiffness and damping arising from the interfacial interaction between the slider and the disk. In this paper, we review different models for predicting contact stiffness based on roughness and layered media and then we report experimental data of both contact stiffness and contact damping of typical head-disk interfaces. It is found that the contact stiffness models (based on roughness alone) overpredict the contact stiffness of actual head-disk interfaces by as much as an order of magnitude. Also, it is found that the contact damping ratio is typically few percent and its behavior is substrate dependent. In addition, the effects of a molecularly thin lubricant and humidity on contact stiffness and damping were experimentally investigated and no significant effects were found.