Characterization of head modulation during touchdown process using magnetic spacing sensitivity analysis

Recent growth in the cloud storage industry has created a massive demand for higher capacity hard disk drives (HDD). A sub-nanometer head media spacing (HMS) remains the most critical pre-requisite to achieve the areal density needed to deliver the next generation HDD products. Designing a robust head-disk interface (HDI) with small physical clearance requires a deeper understanding of slider dynamics, especially when the head flies in proximity to the disk surface. This paper describes a method using the magnetic read-back signal to characterize the head fly-height modulations as it undergoes a transition from a free-flying state to soft contact with the disk surface. A technique based on the magnetic fly-height sensitivity is introduced to identify the transition plane that corresponds to the onset of the touchdown process. Additionally, the proposed magnetic spacing based meteorology is used to study the effect of the air bearing stiffness and lubricant properties on the slider vibrations induced by intermittent head-disk interactions. The ability to accurately determine the transition plane corresponding to minimum stable flying conditions can help design a low clearance head-disk interface.