I. Introduction
The physical clearance between the read-write head and disk in magnetic recording hard disk drives (HDDs) has been continuously decreasing in the past decades in order to meet the ever-increasing demand for higher areal density of stored data. In recent years, thermal flying-height control (TFC) technology has been widely used to achieve an ultra-low physical clearance at the read-write transducers. In this approach, the local area around the read-write transducers is heated during reading or writing operations by use of a heating element imbedded in the air-bearing slider body, resulting in a bulge at the transducer area. The clearance at the transducer location is thus reduced by several nanometers while other parts of the slider stay well separated from the disk [1]–[6]. With the application of TFC technology, current air-bearing sliders can fly at a clearance of nm where the slider is subject to increasing interactions with the disk and thus experiences a much more complicated dynamic.