GB2071696A - Magneto-optical Recording Medium - Google Patents
Magneto-optical Recording Medium Download PDFInfo
- Publication number
- GB2071696A GB2071696A GB8107897A GB8107897A GB2071696A GB 2071696 A GB2071696 A GB 2071696A GB 8107897 A GB8107897 A GB 8107897A GB 8107897 A GB8107897 A GB 8107897A GB 2071696 A GB2071696 A GB 2071696A
- Authority
- GB
- United Kingdom
- Prior art keywords
- thin film
- recording medium
- magnetic
- magneto
- amorphous
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B11/00—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor
- G11B11/10—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field
- G11B11/105—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field using a beam of light or a magnetic field for recording by change of magnetisation and a beam of light for reproducing, i.e. magneto-optical, e.g. light-induced thermomagnetic recording, spin magnetisation recording, Kerr or Faraday effect reproducing
- G11B11/10582—Record carriers characterised by the selection of the material or by the structure or form
- G11B11/10586—Record carriers characterised by the selection of the material or by the structure or form characterised by the selection of the material
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C45/00—Amorphous alloys
- C22C45/02—Amorphous alloys with iron as the major constituent
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F10/00—Thin magnetic films, e.g. of one-domain structure
- H01F10/08—Thin magnetic films, e.g. of one-domain structure characterised by magnetic layers
- H01F10/10—Thin magnetic films, e.g. of one-domain structure characterised by magnetic layers characterised by the composition
- H01F10/12—Thin magnetic films, e.g. of one-domain structure characterised by magnetic layers characterised by the composition being metals or alloys
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F10/00—Thin magnetic films, e.g. of one-domain structure
- H01F10/08—Thin magnetic films, e.g. of one-domain structure characterised by magnetic layers
- H01F10/10—Thin magnetic films, e.g. of one-domain structure characterised by magnetic layers characterised by the composition
- H01F10/12—Thin magnetic films, e.g. of one-domain structure characterised by magnetic layers characterised by the composition being metals or alloys
- H01F10/13—Amorphous metallic alloys, e.g. glassy metals
- H01F10/133—Amorphous metallic alloys, e.g. glassy metals containing rare earth metals
- H01F10/135—Amorphous metallic alloys, e.g. glassy metals containing rare earth metals containing transition metals
- H01F10/136—Amorphous metallic alloys, e.g. glassy metals containing rare earth metals containing transition metals containing iron
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Crystallography & Structural Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Thin Magnetic Films (AREA)
- Optical Recording Or Reproduction (AREA)
Abstract
A magneto-optical recording medium of an amorphous Gd-Tb-Fe ternary alloy thin film having a magnetic easy axis perpendicular to the film surface. The atomic ratio of a combination of Gd and Tb is in the range of 15 to 35 atom%. This recording medium provides both for efficient recording and optical reproduction.
Description
SPECIFICATION
Magneto-optical Recording Medium
The present invention relates to a magnetooptical recording medium for use as for example, a magneto-optical memory or a magnetic recording display element. In particular, the invention pertains to a magnetic thin film recording medium which has a magnetic easy axis perpendicular to the film surface and permits information to be recorded thereon by forming an inverted magnetic domain of a circular or arbitrary configuration and the information to be read out by utilizing a magneto-optical effect such as the magnetic Kerr effect.
In a ferromagnetrc thin film which has a magnetic easy axis in a direction perpendicular to the film surface, it is possible to provide a small inverted magnetic domain which has a reverse magnetic moment from a uniform magnetization in the film surface which is uniformly magnetized with the south ot north pole magnetic field. By representing the presence and absence of the inverted magnetic domain by "1" and "0", such a ferromagnetic thin film can be used as a highdensity magnetic recording medium.On ferromagnetic thin film having such a property, a thin film of the type which has a large coercive force at room temperature and whose Curie point or magnetic compensation temperature is relatively close to room temperature permits recording of information thereon by forming the inverted magnetic domain at a desired position with a light beam by utilization of the Curie point or the magnetic compensation temperature.
Accordingly, such a thin film is now generally used as a beam addressable file memory.
Known ferromagnetic thin films which have a magnetic easy axis perpendicular to the film surface and can be used as beam addressable files include polycrystalline metal films represented by a Mn-Bi thin film, amorphous metal films as of Gd-Co, Gd-Fe, Tb-Fe, Dy
Fe and so forth and compound single crystal thin films represented by GdlG. These ferromagnetic thin films respectively have such merits and demerits as referred to below.
The polycrystalline metal thin films in which information is written by making use of the Curie point, represented by the Mn-Bi thin film, are excellent as magnetic recording media in that they have as large a coercive force as several Kilo
Oerstreds at room temperature, but they are defective in that to write in information calls for a large energy because of high Curie point (in case of the Mn8Bi thin film, Tc=3600C). Further, since they are polycrystalline, it is necessary to make a thin film of a stoichiometrical composition and the fabrication of such a thin film is technically difficult.The amorphous metal thin films of Gd
Co and Gd-Fe in which information is written through utilization of the magnetic compensation point have advantages in that since they are amorphous, they can be formed on an arbitrary substrate and that the magnetic compensation temperature can be freely controlled to some
extent by adding a small amount of impurity. But these amorphous metal thin films are defective in that the coercive force at room temperature is small (300 to 500 Oe), and that recorded information is unstable. In addition, even for the formation of thin films of such a small coercive force, it is necessary to control their composition to within about 1 atom %; accordingly, these films are also not favourable in terms of manufacture.
The compound single crystal thin films represented by GdlG have a serious defect in that they are very costly as compared with the other thin films. An amorphous Tb-Fe or Dy-Fe alloy thin film containing 15 to 30 atom % of Tb or Dy, which has been proposed as a new magnetic thin film recording medium free from the above said defects, has the following merits:
(1) Since this amorphous alloy thin film has a magnetic easy axis perpendicular to the film surface and as large a coercive force as several
Kilo-Oestreds at room temperature, high-density recording of information is possible and the recorded information is very stable.
(2) The amorphous alloy thin film has a large coercive force and permits writing therein a magnetic domain of a desired configuration.
(3) The amorphous alloy thin film has a large coercive force over a wide composition range, and the composition range which provides excellent properties for a magnetic medium is also wide.
Accordingly, no severe limitations are imposed on the thin film composition and the thin film is very easy to manufacture and good in terms of yield.
(4) Since the Curie point is as low as 1 200C in a case of the Tb-Fe thin film and 600C in a case of the Dy-Fe thin film, thermal write in utilizing the Curie point can be achieved with a small amount of energy.
However, the amorphous Tb-Fe and Dy-Fe alloy thin films have the following shortcomings.
With low Curie point, the energy for writing information may be small but the S/N ratio of the information read out by light is low.
An object of the present invention is to provide a magnetic thin film recording medium which is free from the defects of the prior art magnetic thin film magneto-optical recording media having a magnetic easy axis perpendicular to the film surface and from which a light reproduced output can be obtained efficiently.
In accordance with the present invention, there is provided a magneto-optical recording medium of an amorphous Gd-Tb-Fe ternary alloy thin film having a magnetic easy axis perpendicular to the film surface, characterized in that the atomic ratio of a combination of Gd and Tb is in the range of 1 5 to 35 atoms%.
Embodiments of the present invention will hereinafter be described by way of example and by comparison with the prior arts with reference to the accompanying drawings, in which:
Fig. 1 shows the light reproducing characteristics of known amorphous alloy thin films;
Fig. 2 shows light reproducing characteristics of a magnetic recording medium of the present invention and the known amorphous alloy thin films; and
Fig. 3 shows waveforms of reproduced outputs of a prior art amorphous Gd-Fe thin film and a Gd-Te-Fe thin film of the present invention.
In Fig. 1 S (signal) and the S/N ratio for read out of an amorphous alloy thin film by light are shown as functions of the power of a laser used for irradiating the thin film. It appears from Fig. 1 that in terms of optical reproduction the Tb-Fe and
Dy-Fe thin films which have good properties as recording media are inferior to the Gd-Fe thin film which is not an excellent recording medium.
This is a serious defect when the recording medium is used as a magneto-optical memory.
The magneto-optical recording medium of the present invention is an amorphous Gd-Tb-Fe alloy thin film which has a magnetic easy axis perpendicular to the film surface and a Curie point in the range of 120 to 2000C.
For providing sufficient magnetic anisotropy to orient magnetization in a direction perpendicular to the film surface, it is necessary to make the thin film amorphous and this condition is achieved by forming the thin film, by sputtering or vacuum evaporation, on a substrate held at a temperature below room temperature.Further, in order that the magnetization may be stably oriented in the direction perpendicular to the film surface, it is necessary that the film thickness be 1 00A or more and, in order to provide the Curie point in the range of 120 to 2000C as mentioned above, it is necessary that the Gd-Tb-Fe composition is (GdxTb,~x) Fe and restricted in the following range:
0.1 5 < YS0.35 0.001X11.00 The magneto-optical recording medium in this composition range is able to have a magnetic easy axis perpendicular to the film surface and permits very high-density recording.
Although the magneto-optical recording medium of the present invention has a relatively low Curie temperature of 120 to 2000C, it is characterized in that its light reproduced output utilizing the magnetic Kerr effect is larger than the light reproduced outputs obtainable with recording media of the Tb-Fe and Gd-Fe alloys which have substantially the same Curie temperature as the recording medium of the present invention.As seen from Fig. 2, however, the light reproduced output of the Gd-Tb-Fe recording medium, shown in comparison with the
reproduction outputs of the Tb-Fe and Gd-Fe recording media, does not simply lie between the outputs of the Tb-Fe and Gd-Fe recording media but is far larger than either of them. In
contrast, its magnetic properties, for example, its coercive force Hc and Curie temperature Tc are both imtermediate between those of the Gd-Fe and Tb-Fe recording media, as shown in Table 1 below.For instance, an amorphous alloy thin film of Gd.13 Tb.13Fe.74 has a coercive force Hc of 2
KOe and a Curie temperature Tc of 1 800C and permits the writing of information therein with substantially the same energy for heat recording on the Gd-Fe and TtHFe recording media and has the coercive force Hc of 2 KOe for retaining the recorded information, which is equal to the coercive forces of the TbFe and DyFe recording media
Table 1
Composition Tc/ C HclOe Gd.2sFe.7s 1 90 70 Gd.17Tb.14Fe.7 1 90 400 Gd.10Tb.17Fe.73 183 780 Gd.13Tb.13Fe.74 1 80 2000
Tb.23Fe.77 120 2200
As has been described above, the magnetooptical recording medium of the present invention
retains such features of the well-known amorphous Tb-Fe, Gd-Fe and Dy-Fe alloy thin films that it has a magnetic easy axis
perpendicular to the film surface, a large coercive force at room temperature and a Curie point ciose to room temperature and is also easy to
manufacture, and in addition, the magneto-optical
recording medium of the present invention has
the advantage that only its light reproduced
output is larger than the output of any of the prior
art recording media. Accordingly, by employing
the magneto-optical recording medium of the
present invention as a storage medium of a
magneto-optical memory in which information is
written by a light beam and from which the
information is read out by making use of the Kerr
effect, such as, for example, one which is called a
beam addressable file memory, it is possible to
realize an excellent memory device of high
recording density and a good S/N ratio. The write
means is not limited specifically to a light beam
but may also be any means for supplying the
energy necessary for producing an inverted
magnetic domain, such as for example, a needle
type magnetic head, a heat pen or an electronic
beam.
Fig. 3 illustrates examples in which information
was recorded by a magnetized needle on an
amorphous Gd-Fe thin film and a Gd-Tb-Fe thin film of the invention and the information was
read out therefrom utilizing the magnetic K-rr effect. The conditions for reading out the thin
films were exactly the same, but the light
reproduced output of the Gd-Tb-Fe thin film
was very large as compared with the output of the Gd-Fe thin film. This indicates that the thin film
of the present invention is excellent magneto
optical recording medium.
The foregoing description has been given of
the Gd-Tb-Fe ternary alloy film, but it is also
effective to add a small amount of an impurity (for
example, La, Y, Dy, Ho, Er, Bi, Cr, or Mo) for the purpose of further reducing the energy for recording.
Claims (5)
1. A magneto-optical recording medium of an amorphous Gd-Tb-Fe ternary alloy thin film
having a magnetic easy axis perpendicular to the film surface, characterized in that the atomic ratio of a combination of Gd and Tb is in the range of 15 to 35 atom %.
2. A medium as claimed in Claim 1 wherein the amorphous Gd-Tb-Fe ternary alloy has a composition-(GdxTb1~x)yFe1-y in which 0.15 < Y < 0.35 and 0.001X11.00.
3. A medium as claimed in Claim 1 or 2 wherein the amorphous Gd-Tb-Fe ternary thin film contains a small amount of an impurity so as to reduce the energy required for recording.
4. A medium as claimed in Claim 3 wherein said impurity is selected from the group consisting of La, Y, Dy, Ho, Er, Bi, Cr and Mo.
5. A medium as claimed in any preceding claim wherein the thin film thickness is at least 1 0or.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3025180A JPS6032331B2 (en) | 1980-03-12 | 1980-03-12 | magneto-optical recording medium |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2071696A true GB2071696A (en) | 1981-09-23 |
| GB2071696B GB2071696B (en) | 1983-11-16 |
Family
ID=12298485
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8107897A Expired GB2071696B (en) | 1980-03-12 | 1981-03-12 | Magneto-optical recording medium |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPS6032331B2 (en) |
| GB (1) | GB2071696B (en) |
| NL (1) | NL8101143A (en) |
Cited By (24)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2913601A1 (en) * | 1978-04-03 | 1979-10-04 | Goodyear Tire & Rubber | METHOD OF DETERMINING THE DEPTH OF A SEPARATION POINT IN A TIRE |
| DE3309483A1 (en) * | 1982-03-17 | 1983-09-29 | Canon K.K., Tokyo | Magneto-optical recording material |
| FR2543725A1 (en) * | 1983-03-29 | 1984-10-05 | Kokusai Denshin Denwa Co Ltd | MAGNETO-OPTICAL RECORDING MEDIUM |
| EP0125536A2 (en) * | 1983-05-11 | 1984-11-21 | MOVID Information Technology, Inc. | Thermo-magnetic recording materials supporting small stable domains |
| US4489139A (en) * | 1981-01-14 | 1984-12-18 | Sharp Kabushiki Kaisha | Magneto-optic memory medium |
| US4569881A (en) * | 1983-05-17 | 1986-02-11 | Minnesota Mining And Manufacturing Company | Multi-layer amorphous magneto optical recording medium |
| DE3604642A1 (en) * | 1985-03-20 | 1986-10-02 | Hitachi, Ltd., Tokio/Tokyo | Magneto-optical recording medium |
| US4615944A (en) * | 1983-05-17 | 1986-10-07 | Minnesota Mining And Manufacturing Company | Amorphous magneto optical recording medium |
| US4683176A (en) * | 1983-08-15 | 1987-07-28 | Nihonshinku Gijutsu Kabushiki Kaisha | Optical magnetic recording member |
| US4693943A (en) * | 1982-05-10 | 1987-09-15 | Canon Kabushiki Kaisha | Magnetooptical recording medium |
| US4721658A (en) * | 1984-04-12 | 1988-01-26 | Minnesota Mining And Manufacturing Company | Amorphous magneto optical recording medium |
| US4734334A (en) * | 1983-11-05 | 1988-03-29 | Canon Kabushiki Kaisha | Magneto-optical recording medium |
| US4799114A (en) * | 1980-11-01 | 1989-01-17 | Daidotokushuko Kabushiki Kaisha | Thermomagnetic recording carrier and a method for thermomagnetic recording |
| US4822675A (en) * | 1987-01-14 | 1989-04-18 | Minnesota Mining And Manufacturing Company | Stable magneto optic recording medium |
| US4833043A (en) * | 1983-05-17 | 1989-05-23 | Minnesota Mining And Manufacturing Company | Amorphous magneto optical recording medium |
| US4838962A (en) * | 1985-07-12 | 1989-06-13 | Hitachi, Ltd. | Magneto-optical recording medium |
| US4950556A (en) * | 1987-10-26 | 1990-08-21 | Minnesota Mining And Manufacturing Company | Magneto-optic recording medium |
| US5019462A (en) * | 1988-02-02 | 1991-05-28 | Basf Aktiengesellschaft | Sheet-like, multilayer magneto-optical recording material |
| DE3348423C2 (en) * | 1982-05-10 | 1994-11-17 | Canon Kk | Use of an amorphous magnetic quaternary GdTbFeCo alloy for the production of a magneto-optical recording layer |
| DE3348424C2 (en) * | 1982-03-17 | 1996-06-27 | Canon Kk | Terbium:iron:cobalt alloy used as magneto:optic recording material |
| US5595805A (en) * | 1991-07-08 | 1997-01-21 | Sharp Kabushiki Kaisha | Magneto-optical recording medium |
| US6001467A (en) * | 1987-11-26 | 1999-12-14 | Sharp Kabushiki Kaisha | Magneto-optic memory medium |
| US6042954A (en) * | 1996-04-22 | 2000-03-28 | Sharp Kabushiki Kaisha | Magneto-optical recording medium |
| US6139949A (en) * | 1989-02-10 | 2000-10-31 | Mitsubishi Denki Kabushiki Kaisha | Magneto optical recording medium |
Families Citing this family (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS56146207A (en) * | 1980-04-16 | 1981-11-13 | Fuji Photo Film Co Ltd | Magnetic thin-film recording medium |
| JPS5873030A (en) * | 1981-10-27 | 1983-05-02 | Kokusai Denshin Denwa Co Ltd <Kdd> | Optical magnetic recording medium |
| JPS58125251A (en) * | 1982-01-21 | 1983-07-26 | Nippon Hoso Kyokai <Nhk> | Optical and magnetic recording medium |
| JPS58196639A (en) * | 1982-05-10 | 1983-11-16 | Canon Inc | Photothermic and magnetic recording medium |
| JPS58199456A (en) * | 1982-05-17 | 1983-11-19 | Canon Inc | Optical thermomagnetic recording medium |
| JPS5917222A (en) * | 1982-07-21 | 1984-01-28 | Hitachi Ltd | Manufacture of multilayer magnetic thin-film |
| JPS5984358A (en) * | 1982-11-04 | 1984-05-16 | Seiko Instr & Electronics Ltd | Photomagnetic recording medium |
| JPS59178628A (en) * | 1983-03-30 | 1984-10-09 | Canon Inc | Information recording method |
| DE3773531D1 (en) * | 1986-05-14 | 1991-11-14 | Teijin Ltd | MAGNETO-OPTICAL RECORD CARRIER. |
| JP2680586B2 (en) * | 1987-11-26 | 1997-11-19 | シャープ株式会社 | Magneto-optical storage medium |
| CA1333820C (en) * | 1988-09-13 | 1995-01-03 | Masahiko Sekiya | Magneto-optical recording medium |
| CA2017284C (en) * | 1989-07-04 | 1995-10-03 | Kazutomi Suzuki | Optical recording medium |
| JPH0746445B2 (en) * | 1993-10-12 | 1995-05-17 | ダイセル化学工業株式会社 | Magneto-optical recording disk and manufacturing method thereof |
| US7076983B2 (en) | 2001-03-16 | 2006-07-18 | Nakayama Steel Works, Ltd. | Apparatus and method for hot rolling |
-
1980
- 1980-03-12 JP JP3025180A patent/JPS6032331B2/en not_active Expired
-
1981
- 1981-03-10 NL NL8101143A patent/NL8101143A/en not_active Application Discontinuation
- 1981-03-12 GB GB8107897A patent/GB2071696B/en not_active Expired
Cited By (28)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2913601A1 (en) * | 1978-04-03 | 1979-10-04 | Goodyear Tire & Rubber | METHOD OF DETERMINING THE DEPTH OF A SEPARATION POINT IN A TIRE |
| US4799114A (en) * | 1980-11-01 | 1989-01-17 | Daidotokushuko Kabushiki Kaisha | Thermomagnetic recording carrier and a method for thermomagnetic recording |
| US4489139A (en) * | 1981-01-14 | 1984-12-18 | Sharp Kabushiki Kaisha | Magneto-optic memory medium |
| DE3348424C2 (en) * | 1982-03-17 | 1996-06-27 | Canon Kk | Terbium:iron:cobalt alloy used as magneto:optic recording material |
| DE3309483C3 (en) * | 1982-03-17 | 2003-02-27 | Canon Kk | Magneto-optical recording material and its use |
| DE3309483A1 (en) * | 1982-03-17 | 1983-09-29 | Canon K.K., Tokyo | Magneto-optical recording material |
| US4693943A (en) * | 1982-05-10 | 1987-09-15 | Canon Kabushiki Kaisha | Magnetooptical recording medium |
| US5738950A (en) * | 1982-05-10 | 1998-04-14 | Canon Kabushiki Kaisha | Magnetooptical recording medium |
| DE3348423C2 (en) * | 1982-05-10 | 1994-11-17 | Canon Kk | Use of an amorphous magnetic quaternary GdTbFeCo alloy for the production of a magneto-optical recording layer |
| US4612068A (en) * | 1983-03-29 | 1986-09-16 | Kokusai Denshin Denwa Co., Ltd. | Magneto-optical recording medium |
| FR2543725A1 (en) * | 1983-03-29 | 1984-10-05 | Kokusai Denshin Denwa Co Ltd | MAGNETO-OPTICAL RECORDING MEDIUM |
| EP0125536A3 (en) * | 1983-05-11 | 1986-06-25 | MOVID Information Technology, Inc. | Thermo-magnetic recording materials supporting small stable domains |
| EP0125536A2 (en) * | 1983-05-11 | 1984-11-21 | MOVID Information Technology, Inc. | Thermo-magnetic recording materials supporting small stable domains |
| US4833043A (en) * | 1983-05-17 | 1989-05-23 | Minnesota Mining And Manufacturing Company | Amorphous magneto optical recording medium |
| US4569881A (en) * | 1983-05-17 | 1986-02-11 | Minnesota Mining And Manufacturing Company | Multi-layer amorphous magneto optical recording medium |
| US4615944A (en) * | 1983-05-17 | 1986-10-07 | Minnesota Mining And Manufacturing Company | Amorphous magneto optical recording medium |
| US4683176A (en) * | 1983-08-15 | 1987-07-28 | Nihonshinku Gijutsu Kabushiki Kaisha | Optical magnetic recording member |
| US4734334A (en) * | 1983-11-05 | 1988-03-29 | Canon Kabushiki Kaisha | Magneto-optical recording medium |
| US4721658A (en) * | 1984-04-12 | 1988-01-26 | Minnesota Mining And Manufacturing Company | Amorphous magneto optical recording medium |
| DE3604642A1 (en) * | 1985-03-20 | 1986-10-02 | Hitachi, Ltd., Tokio/Tokyo | Magneto-optical recording medium |
| US4838962A (en) * | 1985-07-12 | 1989-06-13 | Hitachi, Ltd. | Magneto-optical recording medium |
| US4822675A (en) * | 1987-01-14 | 1989-04-18 | Minnesota Mining And Manufacturing Company | Stable magneto optic recording medium |
| US4950556A (en) * | 1987-10-26 | 1990-08-21 | Minnesota Mining And Manufacturing Company | Magneto-optic recording medium |
| US6001467A (en) * | 1987-11-26 | 1999-12-14 | Sharp Kabushiki Kaisha | Magneto-optic memory medium |
| US5019462A (en) * | 1988-02-02 | 1991-05-28 | Basf Aktiengesellschaft | Sheet-like, multilayer magneto-optical recording material |
| US6139949A (en) * | 1989-02-10 | 2000-10-31 | Mitsubishi Denki Kabushiki Kaisha | Magneto optical recording medium |
| US5595805A (en) * | 1991-07-08 | 1997-01-21 | Sharp Kabushiki Kaisha | Magneto-optical recording medium |
| US6042954A (en) * | 1996-04-22 | 2000-03-28 | Sharp Kabushiki Kaisha | Magneto-optical recording medium |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2071696B (en) | 1983-11-16 |
| NL8101143A (en) | 1981-10-01 |
| JPS6032331B2 (en) | 1985-07-27 |
| JPS56126907A (en) | 1981-10-05 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PE20 | Patent expired after termination of 20 years |
Effective date: 20010311 |