Editing Disk read-and-write head (section)

{{Short description|Small, movable  part of a disk drive}}
{{more citations needed|date=July 2011}}

[[File:Seagate ST33232A hard disk head and platters detail.jpg|thumb|A hard disk head and arm on a platter]]
[[Image:Rwheadmicro.JPG|thumb|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.]]
[[File:HDD read-write head.jpg|thumb|Read–write head of a {{val|3|u=TB}} hard disk drive manufactured in 2013. The dark rectangular component is the ''slider'' and is {{val|1.25|u=mm}} long.  The platter surface moves past the head from right to left.]]

A '''disk read-and-write head''' is the small part of a [[disk drive]] that moves above the disk platter and transforms the platter's magnetic field into electric current (reads the disk) or, vice versa, transforms electric current into magnetic field (writes the disk).<ref>{{Cite book |author1=Mee, C. |author2=Daniel, Eric D. | title=Magnetic recording technology | date=1996 | publisher=McGraw-Hill | location=New York  | isbn=978-0-07-041276-7 | page=7.1}}</ref>  The heads have gone through a number of changes over the years.

In a hard drive, the heads ''fly'' above the disk surface with clearance of as little as 3 [[nanometre]]s.  The [[flying height]] has been decreasing with each new generation of technology to enable higher [[Areal density (computer storage)|areal density]]. The flying height of the head is controlled by the design of an [[Fluid bearing|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.<ref>{{Cite web|last=August 2011|first=Bestofmedia Team 31|title=Hard Drives 101: Magnetic Storage|url=https://www.tomshardware.com/reviews/hard-drive-magnetic-storage-hdd,3005.html|access-date=2021-06-09|website=Tom's Hardware|date=31 August 2011 |language=en}}</ref> If the head hits the disk's surface, a catastrophic [[head crash]] can result. The heads often have a [[diamond-like carbon]] coating.<ref>https://www.fujitsu.com/global/documents/about/resources/publications/fstj/archives/vol42-1/paper13.pdf {{Bare URL PDF|date=August 2024}}</ref>