Modern hard disk drives may have one or more rotating disks. Each disk may have two disk surfaces in use. Hard disk drives also include a servo controller that drives a voice coil actuator to position a read-write head near a track on the surface of a rotating disk in order to read and/or write data to the track. The read-write head may be a magnetic transducer adapted to read data from and/or write data to the one or more rotating disks. Read operations are generally accomplished by sensing a magnetic field associated with the surface of the disk. Write operations are generally accomplished by selectively magnetizing the surface of the disk. The read-write head communicates with the servo controller, providing feedback, which is used in controlling the read-write head's positioning relative to the track. The read-write head is embedded in a slider, which flies on a thin layer of air, known as an air bearing, a very short distance above the rotating disk surface.
The trend in the hard disk drive industry is to increase the areal density of the rotating disk surfaces. This is usually achieved by decreasing the width of the tracks and reducing the flying height of the read-write head above the rotating disk surface, thus reducing the air bearing. Currently read-write heads fly at about 10 nanometers (nm) from the rotating disk surfaces.