Magnetic recording material refers to the use of magnetic properties and magnetic effects to input (write), record, store and output (read out)image、numberEtcmagnetic material 。It is divided into magnetic recording medium materials andHead material。The former is mainly used to record and store information, while the latter is mainly used to write and read information.
Chinese name
Magnetic recording material
Foreign name
magnetic recording material
Classification
Magnetic recording medium materials and magnetic head materials
Magnetic recording material refers to the use of magnetic properties and magnetic effects to input (write), record, store and output (read out) images
Magnetic recording material
Digital and other informationmagnetic material 。It is divided into magnetic recording medium material and magnetic head material.The former is mainly used to record and store information, while the latter is mainly used to write and read information.
In physics, these products are called magnetic recording media (onlymagnetic powderIs magnetic recording material).In theconsumption structureAmong them, tape accounts for the largest proportion (see table).magnetic recordingIt has high recording density, stability and reliability, and can be used repeatedly,Time baseVariable, wide recording frequency range, fast information writing and reading speed, etc.Widely used in radio, film, television, education, medical treatment, automatic control, geological explorationElectronic computing technology, military, aerospace and daily life.[1]
Historical development
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Magnetic recording material
As early as 1857, the prototype of magnetic tape appeared. At that time, the steel tape of 3mm wide and 0.05mm thick was used.In 1898, W. Pulsen, a Danish, invented a practical magnetic recorder, which uses carbon steel wire with a diameter of 1mm.After continuous improvement, the DC magnetic biasing machine appeared in 1907magnetic recordingThe comprehensive development of technology has laid the foundation.With the development of science and technology and electronic industry, the magnetic recording technology and equipment are constantly improved, and the magnetic recording materials have also been developed accordingly.In 1928, German JA. O'Neill made paper-based tape for the first time, with a tape speed of 76.2cm/s.From this tape into practical use.After Kenzo Nagai of Japan invented the AC magnetic bias method in 1938,magnetic recordingThe technology has been further developed, the tape performance has been brought into play, and the effect has been significantly improved.the Second World WarDuring this period, due to military needs, European and American countries secretly studied magnetic recording technology and made great progress. New technologies and devices such as ring magnetic head and AC magnetic bias method appeared.In 1947, M. Canlas of the United States made γ - Fe2O3, which provides a wide range of material sources for the preparation of various recording materials and is still used to manufacture various types offerric oxidemagnetic powder。Tokyo Communications Industry Corporation of Japan (now Sony Corporation) and Tohoku Metal Corporation of Japan developed tape drives and plastic tape based tapes in 1950 and 1952 respectively.In 1953, Reeves Brothers of the United States successfully developed polyester tape based tapes, which are still widely used.In 1963,NetherlandsPhilipsAt the same time, the birth of the cassette tape made the technology have a fundamental change and develop to video recording.In 1960, Junichi Iwata of Japan invented the metal magnetic powder.In 1966, DuPont developed CrO2 magnetic powder.1970, USAMinnesotaMining and manufacturing companies (3M) launched Co - γ - Fe2O3magnetic powderIn the same year, Sony, Panasonic andVictory CompanyThe 1.9cm (0.75in) video tape used in the jointly produced U-matic video recorder is made of this kind of magnetic powder.In 1973 and 1974, Japan made new cobalt coated magnetic powder with trade names of Avilyn and Beridox.At the same time, digital recording materials continue to emerge.1956 and 1972 IBM（IBM）Hard disks and floppy disks are used as external storage materials in computers and microcomputers respectively.Appearing in the early 1970sMagneto-optical diskAnd cassette recorders made by Sony and Victory in 1975 and 1976Video cassette, makemagnetic recordingNew developments have taken place in technology.Since the 1980sPulse code modulation（PCM）、Vertical recordAnd other new technologiesevaporation The application of magnetic recording materials has entered a new stage with the appearance of new materials such as thin film magnetic tape and metal magnetic tape.
The development history of magnetic recording materials in China is relatively short.In the 1960s, acid process needle like γ - Fe2O3 was developedmagnetic powderIn the 1970s, alkali magnetic powder, cobalt coated γ - Fe2O3 magnetic powder and other modified γ - Fe2O3 magnetic powder were successively developed.At present, more than 100 manufacturers are engaged in the industrial production of magnetic recording materials.[2]
manufacturing process
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① SetMagnetic plasma(The main components aremagnetic powder, adhesives, various additives, organic solvents, etc.)polyesterOr metalSupporterIt is made of coated discontinuous material, also known as coated typeFilm material。This is a kind of magnetic recording material with the largest output, the most widely used and the most mature technology, such asVideotape②takemagnetic material Directly using vacuum coating technologyevaporation The continuous thin film material made on the support body is also called continuous thin film material, such as the micro coated tape that appeared in the early 1980s.
Record form
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① Longitudinal magnetic recording material, recorded inMagnetosphereSignal magnetization direction on surface and recording materialDirection of movementConsistent, such as video tape. ②Transverse magnetic recording material, the signal magnetization direction recorded on the surface of the magnetosphere is perpendicular or nearly perpendicular to the movement direction of the recording material, such asVideotapeEtc. ③Vertical magnetic recording material, the signal magnetization direction recorded on the surface of the magnetosphere is perpendicular to the surface of the recording material, such asMagneto-optical diskEtc.
main performance
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The first is the physical and mechanical properties, mainly referring to the shape, geometric dimensionsmechanical strength。The second is magnetic properties, mainly including: ① residualMagnetic inductionBr, refers to the residual magnetic induction strength of the material after it reaches saturation magnetization and then cancels the magnetization field strengthremanence。BrHigh, high material sensitivity, large output signal. ②CoercivityHc, which is required to eliminate the residual magnetism of materialsmagnetic field intensity，HcThe higher it is, the better it is for high frequency recording, so demagnetization is not difficult. ③Rectangle ratio, refers to the maximum residual magnetic inductionBrmAnd saturation magnetic inductionBmThe ratio ofBrm/Bm, which indicates the rectangularity of the material.High ratio is expected to obtain high-quality records.The third is electrical performance, which varies according to the application.The recorded electrical performance indicators areOptimum magnetic bias, sensitivityDistortion rate、Signal-to-noise ratio, maximum output level, copy effect, degaussing degree, etc.
classification
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Magnetic recording materials are classified into granular and continuous according to morphologyFilm materialThey are divided into metal materials andNon metallic materials。The widely used magnetic recording media are γ - Fe2O3 system materials, in addition to CrO2 system, Fe Co system and Co Cr system materials.The magnetic head materials mainly include Mn Zn system and Ni Zn systemFerrite, Fe Al system, Ni Fe Nb system and Fe Al Si system alloy materials.
Development trend
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With the development of magnetic recording materials, the recording wavelength has been shortened from the original 1000 μ m to less than 1 μ m,HcFrom 102Oe to over 103Oe, the most widely used material is oxidemagnetic powder(mainly γ - Fe2O3, CrO2 and cobalt coated magnetic powder) and alloy magnetic powder.In the past 20 years, the material properties have been improved in the following three ways to meet the requirements of high-density recording: ① seeking for improvementMagnetic anisotropyFor example, new materials such as ultrafine particles, needle shaped magnetic powder with high axial ratio, CrO2 and cobalt coated magnetic powder, and alloy magnetic powder with Hc>1000Oe are used. ②ThinningMagnetosphereAnd improve coating technology, improve Hc, and achieve high-density recording.Two methods are often used, namely, removing oxygen and omitting adhesive.The former is made of metal powder instead of oxide, and the latter is made of film.The alloy film is the result of the combination of these two methods. ③Make fundamental improvement on the recording principle and mode.At present, when the density of general longitudinal records increasesDemagnetizing fieldIt can reduce the signal and generateVertical componentAlthough this shortcoming can be overcome by improving Hc and thinning the magnetosphere, there are some limitations.ThereforeVertical recordThe demagnetizing field produced by the material tends to zero with the increase of density.In addition, high Hc and thin materials are not required for vertical recording.It effectively overcomes the fatal weakness of vertical recording in high-density recording.Vertical recording requires that the material be verticalMagnetosphereSuperficialUniaxial anisotropy。Since 1975, the Co Cr vertical film developed by Junichi Iwata of Japan and the subsequent Co Cr and Ni Fe bilayer films can adapt to vertical recordingnew materials 。In 1977, Junyi Iwata announced the achievement that the linear density reached 7.9 thousand bits per cm (20 thousand bits per inch), while the linear density of hard disk is only 5.9 thousand bits per cm (15 thousand bits per inch).Toshiba has produced 8.9cm (3.5in) vertical floppy disks, and recently developedBarium ferriteVertical magnetizationVideotape, usedmagnetic powderIt is hexagonal plate barium ferrite ultrafine particle, and its recording density is 2 times higher than that of ordinary video tape. Especially in short wavelength recording, its characteristics are better than that of metal tape.verticalmagnetic recordingAnd new vertical magnetic recording materials will have broad prospects in the future high-density recording.[2]
