Magnetic storage and
magnetic recording are terms from
engineeringEngineering is the discipline, art and profession of acquiring and applying technical, scientific and mathematical knowledge to design and implement materials, structures, machines, devices, systems, and processes that safely realize a desired objective or inventions.The American Engineers' Council...
referring to the storage of
dataThe term data means groups of information that represent the qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables...
on a
magnetA magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials and attracts or repels other magnets.A permanent magnet is an object made from a...
ized medium. Magnetic storage uses different patterns of
magnetizationMagnetization, M, is defined as the quantity of magnetic moment per unit volume, V:Here, N is the number of magnetic moments in the sample...
in a magnetizable material to store data and is a form of
non-volatile memoryNon-volatile memory, nonvolatile memory, NVM or non-volatile storage, is computer memory that can retain the stored information even when not powered. Examples of non-volatile memory include read-only memory, flash memory, most types of magnetic computer storage devices Non-volatile memory,...
. The information is accessed using one or more
read/write headsDisk read/write heads are the small parts of a disk drive, that move above the disk platter and transform platter's magnetic field into electrical current or vice versa – transform electrical current into magnetic field...
. As of 2009, magnetic storage media, primarily
hard diskA hard disk drive is a non-volatile storage device that stores digitally encoded data on rapidly rotating platters with magnetic surfaces. Strictly speaking, "drive" refers to the motorized mechanical aspect that is distinct from its medium, such as a tape drive and its tape, or a floppy disk...
s, are widely used to store computer data as well as
audioSound is a travelling wave which is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.- Perception of sound...
and
videoVideo is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion.-History:...
signals.
Magnetic storage and
magnetic recording are terms from
engineeringEngineering is the discipline, art and profession of acquiring and applying technical, scientific and mathematical knowledge to design and implement materials, structures, machines, devices, systems, and processes that safely realize a desired objective or inventions.The American Engineers' Council...
referring to the storage of
dataThe term data means groups of information that represent the qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables...
on a
magnetA magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials and attracts or repels other magnets.A permanent magnet is an object made from a...
ized medium. Magnetic storage uses different patterns of
magnetizationMagnetization, M, is defined as the quantity of magnetic moment per unit volume, V:Here, N is the number of magnetic moments in the sample...
in a magnetizable material to store data and is a form of
non-volatile memoryNon-volatile memory, nonvolatile memory, NVM or non-volatile storage, is computer memory that can retain the stored information even when not powered. Examples of non-volatile memory include read-only memory, flash memory, most types of magnetic computer storage devices Non-volatile memory,...
. The information is accessed using one or more
read/write headsDisk read/write heads are the small parts of a disk drive, that move above the disk platter and transform platter's magnetic field into electrical current or vice versa – transform electrical current into magnetic field...
. As of 2009, magnetic storage media, primarily
hard diskA hard disk drive is a non-volatile storage device that stores digitally encoded data on rapidly rotating platters with magnetic surfaces. Strictly speaking, "drive" refers to the motorized mechanical aspect that is distinct from its medium, such as a tape drive and its tape, or a floppy disk...
s, are widely used to store computer data as well as
audioSound is a travelling wave which is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.- Perception of sound...
and
videoVideo is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion.-History:...
signals. In the field of computing, the term
magnetic storage is preferred and in the field of audio and video production, the term
magnetic recording is more commonly used. The distinction is less technical and more a matter of preference. Other examples of magnetic storage media include
floppy diskA floppy disk is a data storage medium that is composed of a disk of thin, flexible magnetic storage medium encased in a square or rectangular plastic shell. Floppy disks are read and written by a floppy disk drive or FDD, the initials of which should not be confused with "fixed disk drive," which...
s, magnetic recording tape, and magnetic stripes on credit cards.
History
Magnetic storage in the form of audio recording on a wire was publicized by
Oberlin SmithOberlin Smith was an engineer who published one of the earliest works dealing with magnetic recording in 1888. In an article that appeared in the British magazine - Electrical World, he suggested the use of permanent magnetic impressions for the recording of sound...
in 1888. He filed a patent in September, 1878 but did not pursue the idea as his business was machine tools. The first publicly demonstrated (Paris Exposition of 1900) magnetic recorder was invented by
Valdemar PoulsenValdemar Poulsen was a Danish engineer. He developed a magnetic wire recorder in 1899.The magnetic recording was demonstrated in principle as early as 1898 by Valdemar Poulsen in his Telegraphone...
in 1898. Poulsen's device recorded a
signalIn the fields of communications, signal processing, and in electrical engineering more generally, a signal is any time-varying or spatial-varying quantity....
on a wire wrapped around a drum. In 1928,
Fritz PfleumerFritz Pfleumer was a German-Austrian engineer who invented magnetic tape for recording sound.-Biography:...
developed the first magnetic
tape recorderThis article deals mainly with analog tape recorders for audio applications; information on digital recording, recording of video signals, and recording of data can be found in other articles....
. Early magnetic storage devices were designed to record
analogAn Analog or analogue signal is any continuous signal for which the time varying feature of the signal is a representation of some other time varying quantity, i.e analogous to another time varying signal. It differs from a digital signal in terms of small fluctuations in the signal which are...
audio signals. Computer and now most audio and video magnetic storage devices record
digitalA digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...
data.
In old computers, magnetic storage was also used for primary storage in a form of magnetic drum, or core memory,
core rope memoryCore rope memory is a form of read-only memory for computers, first used by early NASA Mars probes and then in the Apollo Guidance Computer designed by MIT and built by Raytheon....
,
thin film memoryThin-film memory is a high-speed variation of core memory developed by Sperry Rand in a government-funded research project.Instead of threading individual ferrite cores on wires, thin-film memory consisted of 4 micrometre thick dots of permalloy, an iron-nickel alloy, deposited on small glass...
,
twistor memoryTwistor is a form of computer memory, similar to core memory, formed by wrapping or closing magnetic tape around a current-carrying wire. Although the developers, Bell Labs, had high hopes for Twistor, it was used for only a brief time in the marketplace between about 1968 and the mid-1970s...
or
bubble memoryBubble memory is a type of non-volatile computer memory that uses a thin film of a magnetic material to hold small magnetized areas, known as bubbles or domains, each of which stores one bit of data...
. Unlike modern computers, magnetic tape was also often used for secondary storage.
Analog recording
Analog recording is based on the fact that remnant magnetization of a given material depends on the magnitude of the applied field. The magnetic material is normally in the form of tape, with the tape in its blank form being initially demagnetized. When recording, the tape runs at a constant speed. The writing head magnetizes the tape with current proportional to the signal. A magnetization distribution is achieved along the magnetic tape. Finally, the distribution of the magnetization can be read out, reproducing the original signal. The magnetic tape is typically made by embedding magnetic particles in a plastic binder on polyester film tape. The commonly used magnetic particles are Iron oxide particles or Chromium oxide and metal particles with size of 0.5 micrometers. Analog recording was very popular in audio and video recording. In the past 20 years, however, tape recording has been gradually replaced by digital recording.
Digital recording
Instead of creating a magnetization distribution in analog recording, digital recording only need two stable magnetic states, which are the +Ms and -Ms on the
hysteresis loopA system with hysteresis has memory. Such a system is said to exhibit path-dependence, or "rate-independent memory". .In a deterministic system with no dynamics or hysteresis, it is possible to predict the system's output at an instant in time, given only its input at that instant in time...
. Examples of digital recording are floppy disks and HDDs. Since digital recording is the main process nowadays and probably in the coming future, the details of magnetic recording will be discussed in the rest of the project using the HDD as an example.
Magneto-optical recording
Magneto-optical recording writes/reads optically. When writing, the magnetic medium is heated locally by a laser, which induces a rapid decrease of coercive field. Then, a small magnetic field can by used to switch the magnetization. The reading process is based on magneto-optical
Kerr effectThe Kerr effect, also called the quadratic electro-optic effect , is a change in the refractive index of a material in response to an applied electric field. The Kerr effect is distinct from the Pockels effect in that the induced index change is directly proportional to the square of the electric...
. The magnetic medium are typically amorphous R-FeCo thin film (R being a rare earth element). Magneto-optical recording is not very popular. One famous example is
MinidiscA MiniDisc is a magneto-optical disc-based data storage device initially intended for storage of up to 80 minutes of digitized audio...
developed by
Sonyis a multinational conglomerate corporation headquartered in Minato, Tokyo, Japan, and one of the world's largest media conglomerates with revenue exceeding ¥ 7.730.0 trillion, or $78.88 billion U.S. . Sony is one of the leading manufacturers of electronics, video, communications, video game...
.
Domain propagation memory
Domain propagation memory is also called
bubble memoryBubble memory is a type of non-volatile computer memory that uses a thin film of a magnetic material to hold small magnetized areas, known as bubbles or domains, each of which stores one bit of data...
. The basic idea is to control domain wall motion in a magnetic medium that free of microstructure. Bubble refers to stable cylindrical domain. The information is then recorded by the presence/absence of bubble domain. Domain propagation memory has high insensitivity to shock and vibration, so its application are usually in space and aeronautics.
Access method
Magnetic storage media can be classified as either
sequential access memoryIn computing, sequential access memory is a class of data storage devices that read their data in sequence. This is in contrast to random access memory where data can be accessed in any order...
or random access memory although in some cases the distinction is not perfectly clear. In the case of magnetic wire, the read/write head only covers a very small part of the recording surface at any given time. Accessing different parts of the wire involves winding the wire forward or backward until the point of interest is found. The time to access this point depends on how far away it is from the starting point. The case of ferrite-core memory is the opposite. Every core location is immediately accessible at any given time.
Hard disks and modern linear serpentine tape drives do not precisely fit into either category. Both have many parallel tracks across the width of the media and the read/write heads take time to switch between tracks and to scan within tracks. Different spots on the storage media take different amounts of time to access. For a hard disk this time is typically less than 10 ms, but tapes might take as much as 100 s.
Current usage
As of 2008, common uses of magnetic storage media are for computer data mass storage on hard disks and the recording of analog audio and video works on
analog tapeMagnetic tape is a medium for magnetic recording generally consisting of a thin magnetizable coating on a long and narrow strip of plastic. Nearly all recording tape is of this type, whether used for recording audio or video or for computer data storage. It was originally developed in Germany,...
. 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.
Digital tapeMagnetic tape has been used for data storage for over 50 years. In this time, many advances in tape formulation, packaging, and data density have been made. Modern magnetic tape is most commonly packaged in cartridges and cassettes. The device that performs actual writing or reading of data is a...
and
tape librariesIn computer storage, a tape library, sometimes called a tape silo, tape robot or tape jukebox, is a storage device which contains one or more tape drives, a number of slots to hold tape cartridges, a barcode reader to identify tape cartridges and an automated method for loading tapes...
are popular for the high capacity data storage of archives and backups.
Floppy diskA floppy disk is a data storage medium that is composed of a disk of thin, flexible magnetic storage medium encased in a square or rectangular plastic shell. Floppy disks are read and written by a floppy disk drive or FDD, the initials of which should not be confused with "fixed disk drive," which...
s see some marginal usage, particularly in dealing with older computer systems and software. Magnetic storage is also widely used in some specific applications, such as bank checks (MICR) and credit/debit cards (
mag stripesA magnetic stripe card is a type of card capable of storing data by modifying the magnetism of tiny iron-based magnetic particles on a band of magnetic material on the card. The magnetic stripe, sometimes called a magstripe, is read by physical contact and swiping past a reading head...
).
Future
A new type of magnetic storage, called
MRAMMagnetoresistive Random Access Memory is a non-volatile computer memory technology, which has been under development since the 1990s. Continued increases in density of existing memory technologies – notably Flash RAM and DRAM – kept it in a niche role in the market, but its proponents...
, is being produced that stores
dataThe term data means groups of information that represent the qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables...
in magnetic bits based on the
tunnel magnetoresistanceThe Tunnel magnetoresistance is a magnetoresistive effect that occurs in magnetic tunnel junctions . This is a component consisting of two ferromagnets separated by a thin insulator. If the insulating layer is thin enough , electrons can tunnel from one ferromagnet into the other...
(TMR) effect. Its advantage is non-volatility, low power usage, and good shock robustness. The 1st generation that was developed was produced by
Everspin TechnologiesFreescale Semiconductor, Inc. is an American semiconductor manufacturer. It was created by the divestiture of the Semiconductor Products Sector of Motorola in 2004. Freescale focuses their integrated circuit products on the automotive, embedded and communications markets...
, and utilized field induced writing. The 2nd generation is being develped through two approaches:
Thermal Assisted SwitchingThermal Assisted Switching, or TAS, is one of the new 2nd generation approaches to MRAM currently being developed. A few different designs have been proposed, but all rely on the idea of reducing the required switching fields by heating...
(TAS) which is currently being developed by
Crocus Technology-Company:Crocus Technology, founded in 2004, is a venture-capital-backed semiconductor startup company developing next generation MRAM technology. Originating in Grenoble, France, Crocus began with an initial grant from CEA and CNRS, leading French research centers, and now has operations both in...
, and
Spin Torque TransferSpin torque transfer writing technology is a technology in which data is written by re-orienting the magnetisation of a thin magnetic layer in a tunnel magnetoresistance element using a spin-polarised current. An electrical current is generally unpolarised , a spin polarised current is one with...
(STT) on which
Crocus-Company:Crocus Technology, founded in 2004, is a venture-capital-backed semiconductor startup company developing next generation MRAM technology. Originating in Grenoble, France, Crocus began with an initial grant from CEA and CNRS, leading French research centers, and now has operations both in...
,
HynixHynix Semiconductor Inc. of South Korea is a memory semiconductor supplier of dynamic random access memory chips and flash memory chips. Formerly known as Hyundai Electronics, the company has manufacturing sites in Korea, the U.S., China and Taiwan...
,
IBMInternational Business Machines Corporation, abbreviated IBM, is a multinational computer technology and IT consulting corporation headquartered in Armonk, Town of North Castle, New York, United States. The company is one of the few information technology companies with a continuous history dating...
, and several other companies are working. However, with storage density and capacity orders of magnitude smaller than an
HDDA hard disk drive is a non-volatile storage device that stores digitally encoded data on rapidly rotating platters with magnetic surfaces. Strictly speaking, "drive" refers to the motorized mechanical aspect that is distinct from its medium, such as a tape drive and its tape, or a floppy disk...
, MRAM is useful in applications where moderate amounts of storage with a need for very frequent updates are required, which
flash memoryFlash memory is a non-volatile computer storage that can be electrically erased and reprogrammed. It is a technology that is primarily used in memory cards and USB flash drives for general storage and transfer of data between computers and other digital products...
cannot support due to its limited write endurance.
See also
- Data storage
Data storage can refer to:* Computer data storage; memory, components, devices and media that retain digital computer data used for computing for some interval of time....
, a broader perspective
- Magnetism
In physics, the term magnetism is used to describe how materials respond on the microscopic level to an applied magnetic field; to categorize the magnetic phase of a material. For example, the most well known form of magnetism is ferromagnetism such that some ferromagnetic materials produce their...
, the phenomenon
- Magnetization
Magnetization, M, is defined as the quantity of magnetic moment per unit volume, V:Here, N is the number of magnetic moments in the sample...
, the property of an object that is affected by magnetism
- Magnetic tape sound recording
Magnetic tape has been used for sound recording for more than 75 years. Tape revolutionized both the radio broadcast and music recording industries. It did this by giving artists and producers the power to record and re-record audio with minimal loss in quality as well as edit and rearrange...
- Disk storage
Disk storage or Disc storage is a general category of a computer storage mechanisms, in which data is recorded on planar, round and rotating surfaces . A disk drive is a peripheral device used to record and retrieve information. Main implementations are hard disks, floppy disks and optical discs...
, which can store data magnetically and by other means
- Marvin Camras
Marvin Camras was an electrical engineer and inventor who was widely influential in the field of magnetic recording.Camras built his first recording device, a wire recorder, in the 1930s for a cousin who was an aspiring singer...
, another innovator in the field
- MRAM
Magnetoresistive Random Access Memory is a non-volatile computer memory technology, which has been under development since the 1990s. Continued increases in density of existing memory technologies – notably Flash RAM and DRAM – kept it in a niche role in the market, but its proponents...
, one of the newest types of magnetic storage
External links