GB2077065A - Magnetooptic memory medium - Google Patents
Magnetooptic memory medium Download PDFInfo
- Publication number
- GB2077065A GB2077065A GB8105358A GB8105358A GB2077065A GB 2077065 A GB2077065 A GB 2077065A GB 8105358 A GB8105358 A GB 8105358A GB 8105358 A GB8105358 A GB 8105358A GB 2077065 A GB2077065 A GB 2077065A
- Authority
- GB
- United Kingdom
- Prior art keywords
- crystallization
- layer
- amorphous material
- writing
- meduim
- 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
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
- G03G5/16—Layers for recording by changing the magnetic properties, e.g. for Curie-point-writing
-
- 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
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
- G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
- G11B7/0938—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following servo format, e.g. guide tracks, pilot signals
-
- 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
Abstract
Disclosed is a new magnetic storage medium including a layer of amorphous material typically GdDyFe whose Curie recording point is lower than its crystallization point (e.g., 120 DEG C for 350 DEG C) to enable crystallization to cause variations in its optical properties such as transmittance or reflectivity for thermomagnetic writing. Reversible recordings are set up on the amorphous material layer by thermomagnetic writing technique for example the Curie point writing, while unchangeable or permanent recordings are set up on the amorphous material layer through laser-activated crystallization of the amorphous material layer.
Description
SPECIFICATION
Magnetooptic memory medium
BACKGROUND OF THE INVENTION
This invention relates to a magnetooptic data storage medium of amorphous magnetic material and more particularly to a magnetooptic data storage meduim including changeable and readable memory locations and unchan
geable memory locations.
In recent years, the use of thin films of amorphous magnetic materials for thermo
magnetic writing, erasing and magnetooptical
reading has received particularly intensive study. This sort of optical memory system can
be classified into the following categories, depending on data storage properties:
(1) it is readable only;
(2) it can hold additional recordings and
readable immediately after writing; and
(3) it is writable, readable and erasable.
Of these three different categories the last is
most suitable for computer applications and typically comprises amorphous magnetic films
as a storage medium.
Furthermore, the methods of writing for the
magnetooptic storage meduim developed to
data are as follows. (a) Curie point writing technique by which the temperature of a
memory bit location is elevated above the
Curie point where magnetizations are de
stroyed. (b) Compensation temperature tech
nique which takes advantage of the coercivity falling when the memory bit location about at the compensation temperature is further
heated. (c) Temperature dependent coercivity technique relying upon the phenomemon where the coercivity varies greatly with a temperature rise. Recording is achieved by
applying a laser beam onto the memory bit
location in the order of 1 umz and thus vary
ing magnetizations in light-activated domains
due to temperature increases.Erasing record
ings demands energy for restoring the original
magnetizations, using the same optical system
as for writing. This sort of amorphous mag
netic material is well known as a changeable optical memory meduim. Reversibility of the
medium, however, results in erasing record
ings upon malfunction or erroneous operation
of a recording system and making data unsta
ble due to fluctuations in the ambient temperature.
OBJECTS AND SUMMARY OF THE INVEN
TION
Accordingly, it is an object of the present
invention to provide a magnetooptic recording
meduim which has a writable and erasable
memory location for thermomagnetic writing, erasing and recording and magnetoptical read
ing and an unchangeable memory location for
only magnetooptical recording.
BRIEF DESCRIPTION OF THE DRAWINGS
For a more complete understanding of the present invention and for further objects and advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings, in which:
Figure 1 is a graph plotting transmittance of a GdDyFe film in the amorphous state and crystallized state overcovered with a SiO2 layer as a function of wavelength;
Figure 2 is a graph showing the relation between coercivity and Curie point;
Figure 3 is a schematic diagram of an optical data storage device using Faraday effect.
Figure 4 is a storage meduim with guide tracks according to the present invention; and
Figure 5 is an enlarged view of the guide tracks in Fig. 4.
DETAILED DESCRIPTION OF THE INVEN
TION
A film of amorphous magnetic material including rare earth metals and transition metals manifests an increase in transmittance and a decrease in reflectivity by crystallization, as is clear from Fig. 1 where the curve A shows the amorphous state of the film and the curve B shows the crystallized state. Of particular interest is GdDyFe which exhibits a remarkable trend to vary its transmittance or reflectivity depending whether it is in the amorphous state or the crystallized state. This leads to the possibility that crystallizing desired ones of bit locations can provide brightness-varying signals in reading out the locations via a light detector and an optical reproduction system (using Faraday effect or the like) can be utilized as it is.It is obvious from Fig. 2 that the Curie point of the amorphous magnetic material GdDyFe is approximately 1 20' and the transmission point from the amorphous to the crystallized state is 350 . There is therefore a difference of temperature sufficient to enable both the Curie point writing (as a changeable memory) and Crystallization writing (as an unchangeable or permanent memory) on a same meduim through the step of varying the intensity of a light source for recording.
In other words, as seen from Fig. 3, a thin film of amorphous GdDyFe (e.g., Gd : Tb : Fe ratio = 0.24: 0.18 :1) and thickness = 500 - 800 ) whose Curie point recording is possible at a temperature significantly lower than that of the crystallization or transition temperature is deposited on a substate 1 of glass or transparent plastic. An example of the substrate 1 used is glass, acryl or polycarbonate. The GdDyFe thin film 1 is overcovered with a protective film 3 of SiO2 (e.g., thickness = 5400 A), thus completing a magnetooptic recording meduim. Then, the memory medium is shaped into a disk which is driven at an appropriate rate by a rotating driving system 4 such as a motor.
To record and fetch data on and from the above-mentioned storage meduim, there is provided an optical memory system which relies upon the Curie point writing using the magnetooptical Faraday effect of the thin film.
In this drawing, a laser 5 typically of He-Ne is provided which releases a laser beam via a light modulator 6 and a polarizer 7 toward an optical system 8 including a mirror for changing the direction of its optical path and a recording lens. The optical system 8 is located vis-a-vis with memory bit locations of the storage meduim to apply the laser beam thereto so that data may be written as the changeable recording or the unchangeable recording, based on the output level of the laser beam. Furthermore, the data fetched from the storage meduim 1 is led to a detector 10 via an optical system 9 including a mirror for changing the optical path and a condensor lens and then to a light detector 11. This results in reading the data from the changeable memory locations and the unchangeable memory locations.
Although the foregoing has set forth the use of the GdDyFe film as a typical example of the amorphous magnetic material, other materials whose recording temperatures are lower than its crystallization points to enable crystallization to cause a difference in transmittance or reflectivity are available for the purpose of the present invention, for example, GdTbFe,
DyFe, TbFe, etc. The other methods of writing and reading other than the above mentioned
Curie point writing and Faraday effect reading are also useful as long as the present invention is concerned.
As noted earlier, the present invention utilizes the temperature dependency of the magnetization properties and crystallization properties of the amorphous magnetic material, thus making it possible to set up both the reversible recordings and unchangeable recordings on the same storage meduim with different conditions of erasing information. More particularly, the permanent recordings are made with no possible destruction of information. In addition, writing and reading require no particular expenditure.
Generally speaking, a high packing density storage meduim has recording tracks each of a width in the order of 1 um. For writing and
reading by the laser beam to be practical, it is essential that the laser beam be spotted on
only a track sought to be written or read and not the other tracks. To this end a precision optical system or a servo system with the help of guide tracks are necessary.
In another preferred aspect of the present
invention, the unchangeable recordings are
effectively utilized as guide tracks for the
laser-addressing technique. Figs 4 and 5 illus
trate a magnetooptic data storage meduim
with crystallized guide tracks. The guide tracks are formed to be flush with recording (reversible) tracks 13 upon laser beam application. In order to form the guide tracks 12 as minute as possible, the laser beam of a short wavelength is employed, for example, Ar laser beam of about 4880 A. Especially, both sides of a respective one of the recording tracks 13 are heated to above the crystallization temperature (typically, 350 C) for the setup of the guide tracks 12.
In the case where the guide tracks 12 are set up along the recording tracks in this manner, the recording tracks 13 are never crystallized to ensure that the recordings are stable even during exposure of the laser beam for the setup of record bits 14 at a temperature near the Curie point (about 1 0O'C). Furthermore, the other recording tracks 13 are not affected by exposure of the laser beam because of the recording tracks being sandwiched between the guide tracks 12.
The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications are intended to be included within the scope of the following claims.
Claims (14)
1. A magnetooptical storage medium comprising a layer of GdDyFe as amorphous magnetic material for thermomagnetic writing.
2. A magnetic storage meduim comprising a layer of amorphous material whose recording temperature is lower than its crystallization point to enable crystallization to cause variations in its optical property for thermomagnetic writing.
3. A magnetic storage meduim compris
ing:
a layer of amorphous material whose recording temperature is lower than its crystallization point to enable crystallization to cause variations in its optical property for thermo
magnetic writing;
reversible recordings set up on said amor
phous material layer; and
unchangeable recordings set up on said
amorphous material layer through crystallization of said amorphous material layer.
4. A magnetooptical storage meduim as
set forth in claim 3 wherein said reversible
recordings are set up by the Curie point writing technique.
5. A magnetic storage meduim compris
ing:
a layer of amorphous material whose rec
ording temperature is lower than its crystalli
zation point to enable crystallization to cause
variations in its optical property for thermo
magnetic writing;
reversible recording tracks set up on said
amorphous material layer; and
unerasable guide tracks set up on said amorphous material layer through crystallization of said amorphous material layer.
6. A magnetooptical storage medium as set forth in claim 5 wherein said recording tracks are flanked with said guide trackes.
7. A magnetooptic storage meduim as set forth in claim 5 wherein said guide tracks are set up by heating said amorphous material layer to above the crystallization point.
8. A magnetooptical storage meduim as set forth in claim 1 wherein said crystallization point is about 350 C where said GdDyFe layer changes from the amorphous state to the crystallized state.
9. A magnetooptical storage meduim as set forth in claim 8 wherein said GdDyFe has a Curie point of about 1 20to.
10. A magnetic storage meduim comprising a layer of GdTbFe whose recording temperature is lower than its crystallization point to enable crystallization to cause variations in its optical property for thermomagnetic writing.
11. A magnetic storage meduim comprising a layer of DyFe whose recording temperature is lower than its crystallization point to enable crystallization to cause variations in its optical property for thermomagnetic writing.
12. A magnetic storage meduim comprising a layer of TbFe whose recording temperature is lower than its crystallization point to enable crystallization to cause variations in its optical property for thermomagnetic writing.
13. A magnetooptical storage medium whose optical properties can be selectively varied to store information in an alterable form and, by selective crystallisation of the medium, in a permanent form.
14. A storage medium substantially as herein described with reference to the accompanying drawings.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2191080A JPS56119951A (en) | 1980-02-23 | 1980-02-23 | Magneto-optical recorder and its production |
JP2598080A JPS56119991A (en) | 1980-02-27 | 1980-02-27 | Optical memory device |
Publications (2)
Publication Number | Publication Date |
---|---|
GB2077065A true GB2077065A (en) | 1981-12-09 |
GB2077065B GB2077065B (en) | 1985-01-09 |
Family
ID=26359048
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB8105358A Expired GB2077065B (en) | 1980-02-23 | 1981-02-20 | Magnetooptic memory medium |
GB08401050A Expired GB2140635B (en) | 1980-02-23 | 1984-01-16 | Magnetooptic memory medium |
Family Applications After (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB08401050A Expired GB2140635B (en) | 1980-02-23 | 1984-01-16 | Magnetooptic memory medium |
Country Status (3)
Country | Link |
---|---|
DE (1) | DE3106653C2 (en) |
FR (1) | FR2476892B1 (en) |
GB (2) | GB2077065B (en) |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3335689A1 (en) * | 1982-09-30 | 1984-04-05 | Ricoh Co., Ltd., Tokyo | Magnetooptical recording material |
GB2157876A (en) * | 1984-04-09 | 1985-10-30 | Victor Company Of Japan | High resolution reproduction of signals from phase transformable discs |
US4737947A (en) * | 1983-06-14 | 1988-04-12 | Canon Kabushiki Kaisha | Recording medium having optomagnetic recording layer and optical recording layer with guide tracks of specific reflectance |
US4751142A (en) * | 1985-09-18 | 1988-06-14 | Kyocera Corporation | Magneto-optical recording element |
US4799114A (en) * | 1980-11-01 | 1989-01-17 | Daidotokushuko Kabushiki Kaisha | Thermomagnetic recording carrier and a method for thermomagnetic recording |
US4923765A (en) * | 1984-10-11 | 1990-05-08 | Hitachi, Ltd. | Magneto-optical recording medium |
US5738950A (en) * | 1982-05-10 | 1998-04-14 | Canon Kabushiki Kaisha | Magnetooptical recording medium |
US5756202A (en) * | 1993-08-04 | 1998-05-26 | U.S. Philips Corporation | Magnetic-optical recording medium |
Families Citing this family (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4414650A (en) * | 1980-06-23 | 1983-11-08 | Sharp Kabushiki Kaisha | Magneto-optic memory element |
CA1190321A (en) * | 1981-10-29 | 1985-07-09 | Toshihisa Deguchi | Magneto-optical head assembly |
DE3309483C3 (en) * | 1982-03-17 | 2003-02-27 | Canon Kk | Magneto-optical recording material and its use |
JPS59178641A (en) * | 1983-03-29 | 1984-10-09 | Kokusai Denshin Denwa Co Ltd <Kdd> | Photomagnetic recording medium |
US4586161A (en) * | 1983-05-11 | 1986-04-29 | General Electric Company | Permanent thermo-magnetic recording of binary digital information |
EP0125536A3 (en) * | 1983-05-11 | 1986-06-25 | MOVID Information Technology, Inc. | Thermo-magnetic recording materials supporting small stable domains |
NL8901345A (en) * | 1989-05-29 | 1990-12-17 | Philips Nv | METHOD AND APPARATUS FOR RECORDING SIGNALS ON A RECORD CARRIER, A METERING METHOD AND MEASURING DEVICE FOR USE IN THE RECORDING METHOD AND RECORD DEVICE, AND A RECORD CARRIER |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE1277344B (en) * | 1964-07-06 | 1968-09-12 | Siemens Ag | Procedure for information storage and memory storage for carrying out the procedure |
BE793138A (en) * | 1971-12-21 | 1973-04-16 | Siemens Ag | MAGNETO-OPTICAL MEMORY LAYER |
NL174591C (en) * | 1973-02-09 | 1984-07-02 | Philips Nv | DISC REGISTRATION CARRIER BODY. |
US3816237A (en) * | 1973-02-26 | 1974-06-11 | Ibm | Optically inactive magneto-optic substrate |
US4126494A (en) * | 1975-10-20 | 1978-11-21 | Kokusai Denshin Denwa Kabushiki Kaisha | Magnetic transfer record film |
JPS52109193A (en) * | 1976-03-11 | 1977-09-13 | Kokusai Denshin Denwa Co Ltd | Magnetoooptic memory medium |
NL7713503A (en) * | 1977-12-07 | 1979-06-11 | Philips Nv | Thermomagnetic information recorder e.g. for laser beams - has active layer of gadolinium, iron and holmium, dysprosium or terbium |
US4412264A (en) * | 1979-10-22 | 1983-10-25 | Kokusai Denshin Denwa Co., Ltd. | Magneto-optic recording medium |
-
1981
- 1981-02-20 GB GB8105358A patent/GB2077065B/en not_active Expired
- 1981-02-23 DE DE19813106653 patent/DE3106653C2/en not_active Expired
- 1981-02-23 FR FR8103542A patent/FR2476892B1/en not_active Expired
-
1984
- 1984-01-16 GB GB08401050A patent/GB2140635B/en not_active Expired
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4799114A (en) * | 1980-11-01 | 1989-01-17 | Daidotokushuko Kabushiki Kaisha | Thermomagnetic recording carrier and a method for thermomagnetic recording |
US5738950A (en) * | 1982-05-10 | 1998-04-14 | Canon Kabushiki Kaisha | Magnetooptical recording medium |
DE3335689A1 (en) * | 1982-09-30 | 1984-04-05 | Ricoh Co., Ltd., Tokyo | Magnetooptical recording material |
US4737947A (en) * | 1983-06-14 | 1988-04-12 | Canon Kabushiki Kaisha | Recording medium having optomagnetic recording layer and optical recording layer with guide tracks of specific reflectance |
GB2157876A (en) * | 1984-04-09 | 1985-10-30 | Victor Company Of Japan | High resolution reproduction of signals from phase transformable discs |
US4923765A (en) * | 1984-10-11 | 1990-05-08 | Hitachi, Ltd. | Magneto-optical recording medium |
US4751142A (en) * | 1985-09-18 | 1988-06-14 | Kyocera Corporation | Magneto-optical recording element |
US5756202A (en) * | 1993-08-04 | 1998-05-26 | U.S. Philips Corporation | Magnetic-optical recording medium |
Also Published As
Publication number | Publication date |
---|---|
GB2140635A (en) | 1984-11-28 |
DE3106653C2 (en) | 1988-05-05 |
DE3106653A1 (en) | 1982-01-21 |
FR2476892B1 (en) | 1987-11-27 |
FR2476892A1 (en) | 1981-08-28 |
GB8401050D0 (en) | 1984-02-15 |
GB2077065B (en) | 1985-01-09 |
GB2140635B (en) | 1985-06-19 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
PE20 | Patent expired after termination of 20 years |
Effective date: 20010219 |