The Heads of a Hard Disk Drive Touch the Surface of the Platter to Read or Write the Data

Small, movable part of a disk drive

A hard disk head and arm on a platter

Microphotograph of a hard disk head. The size of the front face is about 0.3 mm. 1 functional part of the head is the round, orange structure in the center - the lithographically divers copper coil of the write transducer. As well note the electrical connections by wires bonded to gold-plated pads.

Read–write head of a 3TB hard disk drive manufactured in 2013. The nighttime rectangular component is the slider and is 1.25mm long. The read/write head coils are to the left of the slider. Platter surface moves past the head from correct to left.

Disk read/write heads are the small parts of a disk drive which move higher up the disk platter and transform the platter'southward magnetic field into electrical electric current (read the disk) or, vice versa, transform electric electric current into magnetic field (write the deejay).^[ane] The heads have gone through a number of changes over the years.

In a difficult bulldoze, the heads 'fly' above the disk surface with clearance of as fiddling as 3 nanometres. The "flying height" is constantly decreasing to enable higher areal density. The flying height of the caput 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 tiptop constant as the head moves over the surface of the deejay. The air bearings are carefully designed to maintain the same height across the unabridged platter, despite differing speeds relative to the altitude from the center of the platter.^[ii] If the head hits the disk'due south surface, a catastrophic caput crash can effect.

Inductive heads [edit]

Inductive heads use the same chemical element for both reading and writing.

Traditional head [edit]

The heads themselves started out like to the heads in tape recorders—simple devices made out of a tiny C-shaped piece of highly magnetizable fabric such as permalloy or ferrite wrapped in a fine wire coil. When writing, the coil is energized, a potent magnetic field forms in the gap of the C, and the recording surface adjacent to the gap is magnetized. When reading, the magnetized cloth rotates by the heads, the ferrite core concentrates the field, and a current is generated in the ringlet. In the gap the field is very strong and quite narrow. That gap is roughly equal to the thickness of the magnetic media on the recording surface. The gap determines the minimum size of a recorded area on the disk. Ferrite heads are large, and write adequately large features. They must also be flown fairly far from the surface thus requiring stronger fields and larger heads.^[3]

Metal-in-gap (MIG) heads [edit]

Metal-in-gap (MIG) heads are ferrite heads with a pocket-sized piece of metal in the caput gap that concentrates the field. This allows smaller features to be read and written. MIG heads were replaced with thin film heads. Thin motion-picture show heads were electronically similar to ferrite heads and used the aforementioned physics, but they were manufactured using photolithographic processes and thin films of material that allowed fine features to be created.

Thin-film heads [edit]

Offset introduced in 1979 on the IBM 3370 disk drive, thin-film engineering used photolithographic techniques similar to those used on semiconductor devices to fabricate HDD heads with smaller size and greater precision than ferrite-based designs then in use. Thin layers of magnetic (Ni–Fe), insulating, and copper coil wiring materials are built on ceramic substrates that are then physically separated into private read/write heads integrated with their air bearing significantly reducing the manufacturing cost per unit of measurement.^[iv] Thin film heads were much smaller than MIG heads and therefore allowed smaller recorded features to be used. Thin movie heads allowed iii.5 inch drives to reach 4GB storage capacities in 1995. The geometry of the head gap was a compromise between what worked best for reading and what worked all-time for writing.^[3]

Magnetoresistive heads (MR heads) [edit]

The next head improvement in head design was to split the writing element from the reading element allowing the optimization of a thin film element for writing and a dissever caput element for reading. The separate read element uses the magnetoresistive (MR) effect which changes the resistance of a fabric in the presence of magnetic field. These MR heads are able to read very small magnetic features reliably, but tin can not exist used to create the potent field used for writing. The term AMR (Anisotropic MR) is used to distinguish it from the later introduced improvement in MR engineering called GMR (behemothic magnetoresistance) and "TMR" (tunneling magnetoresistance).

The transition to perpendicular magnetic recording (PMR) media has major implications for the write process and the write element of the head construction just less so for the MR read sensor of the head structure.^[5]

AMR heads [edit]

The introduction of the AMR head in 1990 past IBM^[6] led to a menstruum of rapid areal density increases of nearly 100% per yr.

GMR heads [edit]

In 1997 GMR, behemothic magnetoresistive heads started to supervene upon AMR heads.^[6]

Since the 1990s, a number of studies have been done on the effects of jumbo magnetoresistance (CMR), which may permit 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.^{[seven] [8]}

TMR heads [edit]

In 2004, the first drives to use tunneling MR (TMR) heads were introduced past Seagate^[6] allowing 400 GB drives with three disk platters. Seagate introduced TMR heads featuring integrated microscopic heater coils to control the shape of the transducer region of the caput during operation. The heater can exist activated prior to the start of a write operation to ensure proximity of the write pole to the deejay/medium. This improves the written magnetic transitions by ensuring that the head's write field fully saturates the magnetic disk medium. The same thermal actuation approach tin be used to temporarily decrease the separation between the disk medium and the read sensor during the readback process, thus improving signal strength and resolution. By mid-2006 other manufacturers have begun to use like approaches in their products.

See also [edit]

• Head crash

References [edit]

1. ^ Mee, C.; Daniel, Eric D. (1996). Magnetic recording technology. New York: McGraw-Hill. p. 7.1. ISBN978-0-07-041276-7.
2. ^ August 2011, Bestofmedia Team 31. "Hard Drives 101: Magnetic Storage". Tom's Hardware . Retrieved 2021-06-09 .
3. ^ ^{a b} "Read/Write Caput Designs: Ferrite, Metal-In-Gap, And Thin-Film - Hard Drives 101: Magnetic Storage". Tom's Hardware. 2011-08-30. Retrieved 2019-04-13 .
4. ^ "1979: Thin-film heads introduced for large disks". Computer History Museum. December 2, 2015. Retrieved June 19, 2019.
5. ^ IWASAKI, Shun-ichi (February 2009). "Perpendicular magnetic recording—Its development and realization—". Proceedings of the Japan Academy. Series B, Physical and Biological Sciences. 85 (ii): 37–54. Bibcode:2009PJAB...85...37I. doi:10.2183/pjab.85.37. ISSN 0386-2208. PMC3524294. PMID 19212097.
6. ^ ^{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, Mount View, CA. Archived from the original (PDF) on 2015-12-xx. Retrieved 2015-09-25 .
7. ^ "Chemists exploring new material with 'next generation' computer difficult bulldoze possibilities". The University of Aberdeen News. 27 January 2014.
8. ^ Dagotto, Elbio (14 March 2013). "Brief Introduction to Giant Magnetoresistance (GMR)". Nanoscale Phase Separation and Colossal Magnetoresistance: The Physics of Manganites and Related Compounds. Springer Serial in Solid-State Sciences. Vol. 136. Springer Science & Business Media. pp. 395–396. doi:10.1007/978-three-662-05244-0_21. ISBN9783662052440.

External links [edit]

• The PC Guide: Function of the Read/Write Heads
• IBM Research: GMR introduction, animations
• Hitachi Global Storage Technologies: Recording Head Materials

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Source: https://en.wikipedia.org/wiki/Disk_read-and-write_head

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