JPH02156450A - Magneto-optical recorder - Google Patents

Abstract

PURPOSE:To enable the stabilized recording by impressing a magnetic field having such an intensity distribution that a distant part is higher than a part irradiated with a light beam on a medium, where the former is away from the latter and its vicinity along the traveling direction of the light beam. CONSTITUTION:A permanent magnet 13 is provided behind a center protrusion part 12a in the disk moving direction D. Then, this permanent magnet 13 is formed in such a wedge shape that the farther backward the thicker in thickness. These protrusion part 12a and magnet 13 are wound with a coil 14. At the time of recording information, the coil 14 is electrified, and the magnetic field is impressed on the disk 1 by a magnetic field generating device 11. In this case, the magnetic field to be generated has the strongest intensity around the magnet 13. Consequently, magnetic field intensity on the disk 1 is distributed in such a fashion that its position P1 apart from the position P0 irradiated with the beam is higher than the latter along the scanning direction of the light beam. By the magnetic field in this position P1, a 2nd magnetic layer of the disk is initialized. Then, the dual write of information is feasible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a magneto-optical recording device, and more particularly to a magneto-optical recording device that allows information to be overwritten using a medium having a plurality of magnetic layers.

[Prior Art] In recent years, research and development of optical memory elements using laser light as high-density, large-capacity memories have been carried out at a rapid pace. Among these, magneto-optical recording media are highly anticipated as rewritable optical memory devices. Compared to magnetic recording media using conventional magnetic heads, such magneto-optical recording media have the advantage of being capable of high-density recording and non-contact recording and playback. There was a problem in that the recorded portion had to be erased once (it had to be magnetized in one direction).

On the other hand, a magneto-optical recording medium that solves the above-mentioned problems and allows overwriting and an apparatus for recording on this medium have been proposed in Japanese Patent Laid-Open Publication No. 175948/1983. An example of such a magneto-optical recording device is shown in FIG. 1I.

FIG. 11 is a schematic diagram showing the configuration of an overwritable magneto-optical recording device. In the figure, 14 indicates an overwritable magneto-optical disk. This disk 14 has a first magnetic layer on a substrate and a second magnetic layer having a higher Curie temperature and a lower coercive force than the first magnetic layer. It is constructed by laminating magnetic layers.

The disk 14 is rotated by a spindle motor 15. First, the magnetization direction of the second magnetic layer is aligned by the initialization magnetic field generating means 17. Thereafter, recording is performed by irradiating the disk 14 with a light beam whose intensity is modulated between two non-zero values according to the recording information from the light source 16 while a magnetic field is applied by the bias magnetic field generating means 18. Ru.

Here, the initialization magnetic field generation means 17 and the bias magnetic field generation means 18 may be provided at different positions, but when considering the case where these means are inserted into a cartridge containing a disk, etc., they may be installed as shown in FIG. In addition, the configuration is simpler if the light beam is provided in common at the irradiation position of the light beam. In this case, the intensity distribution of the magnetic field applied to the disk 14 is
As shown in FIG. 12, along the scanning direction of the light beam,
It forms a hill with the light beam irradiated area P as the center.

[Problem to be solved by the invention] However, in order to perform stable recording, it is desirable that the bias magnetic field is smaller than the initialization magnetic field.
Therefore, in a device in which these generation means are shared as described above, the bias magnetic field is too large, causing magnetization reversal even in the areas around the recording bit that have not yet reached the recording temperature, which disturbs the shape of the bit. However, there was a problem in that recording noise increased.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art described above and to provide a magneto-optical recording device that has a simple configuration and is capable of stably overwriting information.

[Means for Solving the Problems] The above object of the present invention is to provide a means for irradiating an overwritable magneto-optical recording medium with a light beam whose intensity is modulated between two non-zero values according to recorded information; In a magneto-optical recording device comprising means for scanning the light beam relative to a medium, and means for applying a magnetic field to a portion of the medium to which the light beam is irradiated and in the vicinity thereof, the magnetic field applying means: This is achieved by configuring the medium to apply a magnetic field having an intensity distribution such that the strength is higher at a portion away from the beam irradiation portion than at the beam irradiation portion along the scanning direction of the light beam.

[Example] Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic diagram showing one embodiment of a magneto-optical recording device of the present invention. In this embodiment, a configuration is shown in which both recording and reproduction of recorded information are possible. In the figure, I is a disk-shaped magneto-optical recording medium (magneto-optical disk), 2 is a spindle motor that rotates the disk l, and 3 is an optical head that irradiates the disk l with a light beam 19. The optical head 3 includes a laser light source 4 consisting of a semiconductor laser or the like. Collimator lens 5. Beam splitter 6, objective lens 7, sensor lens 9. It contains an analyzer 8 and a photodetector IO, and is moved in the radial direction of the disk indicated by an arrow R by a mechanism not shown. The objective lens 7 also moves in the optical axis direction and in the direction perpendicular to the optical axis in accordance with a control signal detected by a photodetector using a well-known method, and performs so-called auto-tracking (AT) and auto-focusing (AF). Laser light source 4
is driven by a laser drive circuit (not shown), and emits a light beam 19 whose intensity is modulated between two non-zero values according to recorded information.

At a position facing the optical head 3 with the disk l in between, there is an R
A magnetic field generating means 11 having a length equivalent to the recording area of the disk in the direction is provided, and applies a magnetic field to the portion of the disk 1 that is irradiated with the light beam 19 and its vicinity.

FIG. 2 is a cross-sectional view of the magnetic field generating means 11 taken along the light beam scanning direction. In FIG.
The central protrusion 12a is arranged so as to face the light beam irradiation position of the disk l. A permanent magnet 13 is provided behind the central protrusion 12a in the disk movement direction. Moreover, the further this permanent magnet 13 goes toward the rear, the more
It is shaped like a thick wedge. A coil 14 is wound around the central protrusion 12a and the permanent magnet 13.

When recording information, a current is passed through the coil 14, and the magnetic field generating means 11 applies a magnetic field to the disk l. On this occasion,
The generated magnetic field is strongest around the permanent magnet 13. Therefore, as shown in FIG. 3, the magnetic field strength distribution on the disk 1 is higher at a position P+, which is farther away from the beam irradiation position P0, than at the beam irradiation position P0 along the light beam scanning direction. The magnetic field at position P initializes the second magnetic field of the disk, as will be described later.

In FIG. 3, the horizontal axis represents the position on the disk along the light beam scanning direction, and the vertical axis represents the magnetic flux density.

Here, the intensity of the initialization magnetic field HE at position P1 needs to be greater than the sum of the coercive force of the second magnetic layer and the exchange coupling force that the second magnetic layer receives from the first magnetic layer, which will be described later. For this reason, it is desirable to set Oe to 1 to 2.
On the other hand, the strength of the bias magnetic field Ha at position P0 is 0
．． It is preferable to set it in the range of 1 to 0.6 KOs, because if the magnetic field strength is less than 0.1KOe, the formation of recording bits will be insufficient, and if it is more than 0.6KOs, as mentioned above, This is because recording noise increases.

In the following, information recording by the apparatus of the present invention will be explained.

FIG. 4 is a schematic cross-sectional view showing an example of the configuration of a magneto-optical recording medium used in the present invention. The magneto-optical disk 1 has 5 disks on a transparent substrate 20 made of glass, plastic, etc.
It is constructed by sequentially laminating a lower bow layer 21, a first magnetic layer 22, and a second magnetic layer 23 made of a dielectric material such as isN4. Further, a protective layer 24 made of a dielectric material such as 5iJn is further formed on the second magnetic M23, and is bonded to a protective plate 26 via an adhesive layer 25.

The first magnetic layer 22 has a low Curie temperature (TL) and high coercive force (HH) at room temperature, and the second magnetic layer 23 has a high Curie temperature (TH) and low coercive force (HL) at room temperature.
). Further, the second magnetic layer 23 has a compensation temperature (TcoMP) between T and TH. here,"
"High" and "low" represent a relative relationship when comparing both magnetic layers.

These relationships are illustrated in FIG. 5.

In FIG. 5, C1 and C2 indicate the characteristics of the first and second magnetic layers, respectively. Further, these magnetic layers are exchange coupled.

Usually, the TL of the first magnetic layer 22 is 70 to 180°C, the HH is 3 to 15 Oe, and the second magnetic layer 22 is 100
~400°C, and Hl is preferably within a range of about 0.3 to 2 KOe.

Materials that exhibit perpendicular magnetic anisotropy and magneto-optical effects can be used as the material for each magnetic layer, but GoCo, Gd
Fe, TbFe, DyFe, GdTbFe, T
bDyFe.

Amorphous magnetic alloys of rare earth elements and transition metal elements, such as TbFeCo, GdTbCo, and GdTbFeCo, are preferred.

FIG. 6 shows the state of recording using the above-mentioned medium. In the figure, 22 indicates a first magnetic layer, and 23 indicates a second magnetic layer. Each of 44a to 44g indicates the state of magnetization of both magnetic layers.During the recording process, the coercive force is sufficient to magnetize the second magnetic layer in one direction at a position away from the beam irradiation part. An initialization magnetic field H7 of a magnitude that does not reverse the direction of magnetization of the first m-type layer of the HH is applied downward;
Furthermore, a bias magnetic field H, which assists recording in the second magnetic layer, is applied downward in the beam irradiation section.

Before explaining the recording process according to the process, an overview of the states represented by 44a to 44g and the state of the transition process between each state will first be explained to aid in understanding.

44a and 44g show a binary recording state at room temperature, and by heating with laser light, 44b, 4
The temperature increases at 4c and 44d. 44b and 44f,
44c and 44e show different states at approximately the same temperature. In the figure, → indicates a magnetization process that is reversible with respect to temperature;
- or - indicates an irreversible magnetization process. Also, 44b and 4
A second magnetic compensation temperature exists between 4c or 44e and 44f. The example in FIG. 6 shows a case where the first magnetic layer has dominant rare earth lattice magnetization and the second magnetic layer also has dominant rare earth lattice magnetization. In this case, 44g where the magnetization of both layers is parallel due to exchange interaction between the two layers is a stable state, and 44a where the magnetization is antiparallel is an unstable state,
In this unstable state 44a, an interfacial domain wall exists. However, it is necessary to adjust the coercive force of the second ifl layer so that an unstable state can be maintained even when the magnetic field is zero.

At room temperature (44a, 44g), the second
The magnetization of the magnetic layer is always directed downward in the figure due to the external magnetic field HE.

Next, the recording process will be explained according to the process.

When the temperature is increased from the state 44a, the coercive force of the first magnetic layer decreases and the coercive force of the second magnetic layer increases, as shown in FIG. Then, because the magnetization of both layers tends to become parallel due to exchange interaction, the magnetization of the first magnetic layer is reversed and 4
If you look down like 4b and lower the temperature from this state,
It cools down without changing its magnetization state and shifts to a state of 44 g.

After increasing the temperature from the 44g state and reaching the 44b state, even if the temperature is lowered, it still returns to the 44g state. That is, 4
By applying a laser power corresponding to the temperature of 4b,
Both the state of 44a and the state of 44g shift to the state of 44g.

Next, when the temperature is further increased from the state 44b and reaches the state 44c beyond the compensation temperature Tcovp of the second ffl calendar, the magnetization of the second magnetic layer is reversibly reversed. When the temperature is further increased, the coercive force of the second magnetic layer becomes smaller and is reversed as shown in 44d by the bias magnetic field H. When the temperature is lowered from this state, the magnetization state remains unchanged and TCOIIF
When the temperature is exceeded, the magnetization of the second Mi layer is reversibly reversed. Before and after that, the magnetization of the first magnetic layer is generated upward due to exchange interaction, cooled to room temperature, and the second m-type layer again has a small coercive force, which is reversed by the external magnetic field HE. However, at this time, since the coercive force of the first IIII layer is large, the recording state is maintained without being reversed by the external magnetic field Ht. That is, by applying laser power corresponding to the temperature of 44d, both the state of 44a and the state of 44g become 4.
Move to state 4a.

Therefore, different magnetization states can be obtained by applying different laser powers, which means that overwriting has been realized.

The example in FIG. 7 shows a case where the 11th itl polarity has dominant transition metal sublattice magnetization and the second magnetic layer has dominant rare earth sublattice magnetization. In this case, due to the exchange interaction between both layers, 45a, where the magnetizations of both layers are antiparallel, is a stable state, and 45g, where the magnetizations are parallel, is an unstable state, and in this unstable state 45g, an interface wall exists. do. As in the case of Figure 6, 4
By applying a laser power corresponding to the temperature of 5b,
Both the state 45a and the state 45g shift to the state 45a, and by applying the laser power corresponding to the temperature of 45d, both the state 45a and the state 45g shift to the state 45g. Therefore, different magnetization states can be obtained by applying different laser powers. In other words, this means that overwriting has been realized.

8 to 10 are schematic cross-sectional views showing modified examples of the magnetic field generating means applied to the apparatus of the present invention, respectively. In the example of FIG. 8, the distance between the magnet 27 and the disk l is
By moving the beam closer and farther away from the beam irradiation section along the scanning direction 9, a magnetic field having an intensity distribution as shown in FIG. 3 is obtained.

On the other hand, in the example shown in FIG. 9, the shape of the magnet 28 is wedge-shaped,
The wedge becomes thicker as it moves away from the portion to be irradiated by the beam in the beam scanning direction. In addition, as shown in Figure 10, magnets 29 and 30 made of different materials are bonded together with adhesive and lined up in the beam scanning direction, and a stronger magnetic field is applied to the disk at a position away from the beam irradiation part than from the beam irradiation part. In the example of FIG. 1O, these magnets are placed on the optical head side, and the relatively weak magnet 29 has a
A hole is made through which the light beam 19 passes. Also, in the above explanation, the initialization magnetic field Hz and the bias magnetic field Ha are in the same direction, but if these directions are opposite (
If the second magnetic layer does not have a compensation temperature between Tt and To, the magnetic poles of the magnets 29 and 30 may be oriented in opposite directions as shown in FIG. 1O.

In addition to the embodiments described above, the present invention can be applied in various ways. For example, in the embodiments, the initialization of the medium was performed behind the light beam irradiation position, but it can be performed in front of the light beam irradiation position. It may be configured to generate a magnetic field with an intensity distribution that is higher in front of the beam irradiation part than in the scanning direction. Also, the shape of the medium is not limited to a disk shape, but may be a tape shape or a card shape. It can also be applied to devices that handle media.

[Effects of the Invention] As described above, the present invention provides a magneto-optical recording device that allows overwriting, in which a portion of a medium that is irradiated with a light beam and the vicinity thereof is exposed to a light beam from a beam irradiation unit along the traveling direction of the light beam. However, stable recording is possible by providing a means for applying a magnetic field having an intensity distribution such that the intensity is higher in areas farther away. Furthermore, since the optical head can be moved closer to or away from the medium at a position close to the optical head, the device configuration is simple and is particularly suitable for devices that handle media contained in cartridges.

[Brief explanation of the drawing]

1 is a schematic diagram showing an embodiment of the magneto-optical recording device of the present invention, FIG. 2 is a schematic cross-sectional view showing the configuration of the magnetic field generating means in the device of FIG. 1, and FIG. 3 is the device of FIG. 1. FIG. 4 is a schematic cross-sectional view showing an example of the configuration of a magneto-optical recording medium used in the present invention; FIG. 5 is a diagram showing changes in coercive force due to temperature of the magnetic layer in FIG. 4; 6 and 7 are diagrams for explaining the recording process using the device of the present invention, respectively, and FIGS. 8 to 10 respectively show modified examples of the magnetic field generating means applied to the device of the present invention. Schematic cross-sectional view, 1st! The figure is a schematic diagram showing the configuration of a conventional magneto-optical recording device, and FIG. 12 is a diagram showing the magnetic field strength distribution in the device of FIG. 11. DESCRIPTION OF SYMBOLS 1... Magneto-optical disk, 2... Spindle motor, 3... Optical head, 11... Magnetic field generating means, 12
...Yoke, 13...Permanent magnet, 14...
・Coil, 19...Light beam. Figure 1 Figure 3! IA2 figure 4 figure 5 figure 2 & m6 figure 11 figure 12 figure 9 beam kjhi town direction yA8 figure procedural amendment (voluntary) September 29, 1997

Claims (1)

[Claims] (1) A means for irradiating an overwritable magneto-optical recording medium with a light beam whose intensity is modulated between two non-zero values according to recorded information, and scanning the light beam relative to the medium. and means for applying a magnetic field to a portion of the medium that is irradiated with the light beam and in the vicinity thereof, wherein the magnetic field applying means applies the beam to the medium along the scanning direction of the light beam. A magneto-optical recording device characterized in that a magnetic field is applied with an intensity distribution such that the intensity distribution is higher in a portion remote from an irradiation portion than in an irradiation portion.