Disk read-and-write head
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A disk read-and-write head is the small part of a
In a hard drive, the heads fly above the disk surface with clearance of as little as 3
Inductive heads
Inductive heads use the same element for both reading and writing.
Traditional head
The heads themselves started out similar to the heads in
Metal-in-gap (MIG) heads
Metal-in-gap (MIG) heads are ferrite heads with a small piece of metal in the head gap that concentrates the field. This allows smaller features to be read and written. MIG heads were replaced by thin-film heads.
Thin-film heads
First introduced in 1979 on the
Magnetoresistive heads (MR heads)
The next head improvement in head design was to separate the writing element from the reading element allowing the optimization of a thin-film element for writing and a separate thin-film head element for reading. The separate read element uses the magnetoresistive (MR) effect which changes the resistance of a material in the presence of magnetic field. These MR heads are able to read very small magnetic features reliably, but can not be used to create the strong field used for writing. The term AMR (Anisotropic MR) is used to distinguish it from the later introduced improvement in MR technology called GMR (giant magnetoresistance) and "TMR" (tunneling magnetoresistance).
The transition to
AMR heads
The introduction of the AMR head in 1990 by IBM[7] led to a period of rapid areal density increases of about 100% per year.
GMR heads
In 1997 GMR, giant magnetoresistive heads started to replace AMR heads.[7]
Since the 1990s, a number of studies have been done on the effects of colossal magnetoresistance (CMR), which may allow for even greater increases in density. But so far it has not led to practical applications because it requires low temperatures and large equipment size.[8][9]
TMR heads
In 2004, the first drives to use
See also
- Applied Magnetics Corporation, once the largest supplier of disk heads
- Tape head
References
- ISBN 978-0-07-041276-7.
- ^ August 2011, Bestofmedia Team 31. "Hard Drives 101: Magnetic Storage". Tom's Hardware. Retrieved 2021-06-09.
{{cite web}}
: CS1 maint: numeric names: authors list (link) - ^ https://www.fujitsu.com/global/documents/about/resources/publications/fstj/archives/vol42-1/paper13.pdf
- ^ a b "Read/Write Head Designs: Ferrite, Metal-In-Gap, And Thin-Film - Hard Drives 101: Magnetic Storage". Tom's Hardware. 2011-08-30. Retrieved 2019-04-13.
- ^ "1979: Thin-film heads introduced for large disks". Computer History Museum. December 2, 2015. Retrieved June 19, 2019.
- PMID 19212097.
- ^ a b c Christopher H. Bajorek (November 2014). "Magnetoresistive (MR) Heads and the Earliest MR Head-Based Disk Drives: Sawmill and Corsair" (PDF). Computer History Museum, Mountain View, CA. Archived from the original (PDF) on 2015-12-20. Retrieved 2015-09-25.
- ^ "Chemists exploring new material with 'next generation' computer hard drive possibilities". The University of Aberdeen News. 27 January 2014.
- ISBN 9783662052440.
External links
- The PC Guide: Function of the Read/Write Heads
- IBM Research: GMR introduction, animations Archived 2012-01-11 at the Wayback Machine
- Hitachi Global Storage Technologies: Recording Head Materials Archived 2012-03-30 at the Wayback Machine