Magnetic storage
Magnetic storage uses different patterns of magnetisation in a magnetizable material to store data and is a form of non-volatile memory.
Magnetic storage media, primarily hard disks, are widely used to store computer data as well as audio and video signals.
[citation needed] Magnetic storage in the form of wire recording—audio recording on a wire—was publicized by Oberlin Smith in the Sept 8, 1888 issue of Electrical World.
[1] Smith had previously filed a patent in September, 1878 but found no opportunity to pursue the idea as his business was machine tools.
[citation needed] Information is written to and read from the storage medium as it moves past devices called read-and-write heads that operate very close (often tens of nanometers) over the magnetic surface.
[2] For reliable storage of data, the recording material needs to resist self-demagnetisation, which occurs when the magnetic domains repel each other.
The record and playback head are mounted on a block called a slider, and the surface next to the platter is shaped to keep it just barely out of contact.
[citation needed] Analog recording is based on the fact that remnant magnetisation of a given material depends on the magnitude of the applied field.
When writing, the magnetic medium is heated locally by a laser, which induces a rapid decrease of coercive field.
The magnetic medium are typically amorphous R-Fe-Co thin film (R being a rare earth element).
The basic idea is to control domain wall motion in a magnetic medium that is free of microstructure.
Domain propagation memory has high insensitivity to shock and vibration, so its application is usually in space and aeronautics.
In the case of magnetic wire, the read/write head only covers a very small part of the recording surface at any given time.
[citation needed] Hard disks and modern linear serpentine tape drives do not precisely fit into either category.
Since much of audio and video production is moving to digital systems, the usage of hard disks is expected to increase at the expense of analog tape.
Magnetic storage is also widely used in some specific applications, such as bank cheques (MICR) and credit/debit cards (mag stripes).
[10] However, with storage density and capacity orders of magnitude smaller than an HDD, MRAM is useful in applications where moderate amounts of storage with a need for very frequent updates are required, which flash memory cannot support due to its limited write endurance.
[11] Research is also being done by Aleksei Kimel at Radboud University in the Netherlands[12] towards the possibility of using terahertz radiation rather than using standard electropulses for writing data on magnetic storage media.
