Disk read-and-write head

A disk read-and-write head is the small part of a disk drive which moves above the disk platter and transforms the platter's magnetic field into electrical current (reads the disk) or, vice versa, transforms electrical current into magnetic field (writes the disk).[1] The heads have gone through a number of changes over the years.

A hard disk head and arm on a platter
Microphotograph of a hard disk head. The size of the front edge is about 0.3 * 1.2 mm. The functional part of the head is the round, orange structure in the middle. Also note the connection wires bonded to gold-plated pads.
Read–write head of a 3 TB hard disk drive manufactured in 2013. The dark rectangular component is the slider and is 1.25 mm long. The read/write head coils are to the left of the slider. The platter surface moves past the head from right to left.

In a hard drive, the heads fly above the disk surface with clearance of as little as 3 nanometres. The flying height has been decreasing with each new generation of technology to enable higher areal density. The flying height of the head is controlled by the design of an air bearing etched onto the disk-facing surface of the slider. The role of the air bearing is to maintain the flying height constant as the head moves over the surface of the disk. The air bearings are carefully designed to maintain the same height across the entire platter, despite differing speeds depending on the head distance from the center of the platter.[2] If the head hits the disk's surface, a catastrophic head crash can result.

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