Magnetic storage materials are a kind of materials that store information by using rectangular hysteresis loops or changes in magnetic momentsmagnetic material 。The material will be magnetized under the induction of magnetic field H, forming a magnetic dipole, or magnetic moment.The magnetic moment M in unit volume is called magnetization.Magnetic materials (especially ferromagnetic materials, also called strong magnetic materials) are particularly sensitive to external magnetic fieldsMagnetizationM large.The relationship between the M of magnetic materials and the magnetic field day is very complexMagnetization curveandHysteresis loopTo describe.
Chinese name
Magnetic storage material
Foreign name
Magnetic storage material
Principle
Using rectangular hysteresis loop to store information
Magnetization
Magnetic moment in unit volume
Features
Particularly sensitive to external magnetic field, with high magnetization
The key component of computer - memory is made of magnetic storage materials.magnetic material Because its two magnetization states are very suitable for binary numbers 0 and l, and are convenient for transmission through magnetoelectric conversion, it is suitable for making memories.Bubble memory is an ideal memory.The so-called bubble is actually a cylindrical magnetic unit (or domain).In some very thin magnetic materials, if a magnetic field is applied perpendicular to the direction of the sheet, the originally sinuous strip magnetic domain will shrink. When the magnetic field reaches a certain size, it will shrink into a cylindrical shape.These cylindrical magnetic domains appear round on the surface of the material, as if there are a group of bubbles floating on the water surface, and they will move back and forth under the action of the magnetic field, hence the name.If the presence and absence of magnetic bubbles are used to represent the information of 1 and 0, the generation, disappearance, transmission, splitting, and interaction of magnetic bubbles can be controlled by controlling the circuit or magnetic circuit on the material, so as to complete the functions of information storage, recording, logic operation, and so on.[1]
Magnetic bubble storage material
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There are not many materials that can be used for magnetic bubble storage, usually hexagonal ferrite (MFetwelveOnineteen）(M stands for alkali metal), iron fluoride (FeFthree）Iron borate (FeBOthree）Rare earth orthoferrite, etc.The materials used as bubble devices also need to be very thin (below 15 μ m) single crystals.The current development focus is to improve the bubble density, bubble mobility and temperature stability of materials.[1]
classification
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Most substances in nature have certain magnetism, but practical magnetic materials are generally strongerFerromagnetic material。Such materials are particularly sensitive to the external magnetic field. When they are in the external magnetic field, they will be magnetized and form magnetic dipoles due to magnetic induction.According to the shape and characteristics of the hysteresis loop, it can be divided into the following categories:
(2) Permanent magnet materials.Rare earth cobalt, neodymium iron boron and other metal permanent magnetic materials and ferrite permanent magnets are commonly used.
(3) Moment magnetic material.Its hysteresis loop has a rectangular shape and is mainly used for magnetic recording andMagnetic storage technology, used extensively asMagnetic recording medium, magnetic headComputer memoryThe memory element in the and the control element in the automatic control device.
(4) Gyromagnetic material.Refers to a class with gyromagnetic effect in microwaveFerrite material, used to manufacture various microwaves/Millimeter wave device。
(5) Piezomagnetic materials.When a material is magnetized, its shape and size will always change elastically.That is, there is a strong magnetostrictive effect for manufacturingElectroacoustic transducer。In addition, in order to meet the needs of rapid development of information technologymagnetic material The function has been greatly improved, and many new magnetic materials have been developed, such as giant magnetoresistance materials.[1]
stored procedure
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The magnetic medium moves tangentially with a ring electromagnet in a fixed direction at a constant speed. When the signal current to be recorded is connected to the magnetic head coil, the magnetic head gap will generate a magnetic field whose intensity is modulated by the signal.The magnetic field magnetizes the magnetic material distributed on the medium, producing remanence.Since the speed of the medium and the head remains unchanged, the distribution of residual magnetism along the direction of the medium movement directly reflects the change law of the signal.That is, the recording head induces and feeds into the mediumRemanent magnetizationThe change of signal current with time is transformed into the change of residual magnetization with distance and stored.The medium recording the signal will produce a certain magnetic field. A pickup coil is placed near the medium to make the medium move at a constant speed relative to the pickup coil. In the pickup coil, a magnetic flux modulated by the magnetic field generated by the magnetic material in the medium will be induced. The magnetic flux is proportional to the magnetization of the magnetic material in the medium.Magnetic storage method can be used to record various types of signals.Such as the earliest and most widely used audio signal recording.The frequency of audio signal is low, and the movement speed of medium is slow during recording or playback.howeveraudio frequencySignal recording requires good linearity and high signal-to-noise ratio.Now, magnetic storage is also used to record video signals, that is, to record images.Usually usedfrequency modulationSignal to record video images, high frequency, requires high relative motion speed between the head and the media.It is usually realized by rotating magnetic head.Magnetic storage is also widely used in digital storage. Tape and disk are the common ways of magnetic storage to record digital signals.In principle, both audio and video signals can be recorded by digital magnetic storage.In fact, today, with the rapid development of Internet search technology, massive amounts of information are stored on disk array servers for retrieval and use by astronauts from all over the world, even those leaving the earth.These data include text, audio, video, and other information that can be digitized.[2]
