JP2714085B2 - Information recording method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recording information on a recording medium using the interaction between light and magnetism.

2. Description of the Related Art As a memory using the above method, there is, for example, a magneto-optical disk device. Magneto-optical disk devices have attracted attention due to their large storage capacity and erasable / rewritable data. In addition, studies are being made on overwriting (overwriting) to further increase the data transfer speed and studies to increase the storage capacity.

The overwriting method includes a magnetic field modulation method in which an external magnetic field is modulated according to recording information while irradiating a constant laser power, and applied to a medium, thereby reversing the magnetization of the recording layer to form a pit, A light that modulates the binary laser power corresponding to recording and erasing according to recording information while applying a constant external magnetic field, and irradiates the medium, thereby inverting the magnetization of the recording layer to form a pit. There is a modulation method.

However, in the above-described magnetic field modulation method, it is difficult to modulate a large magnetic field at high speed and apply it to a medium because the distance between the magnetic head and the recording layer is large. Further, in principle, the formed pit has an arrowhead shape, which causes a problem of edge variation and unerased portion, which makes it difficult to record the pit length.

Even in the optical modulation method, there are problems such as unerased data and a decrease in C / N ratio, and it is also difficult to record a pit length. Also, record, erase,
The control of the semiconductor laser is complicated because three levels of power for reproduction are required.

Meanwhile, IBM Technical Disclosure Bulletin Vol.16, No.17
December 1973, pages 2365-2366, using a two-layer iron oxide disc with a different coercive force, first record the track of the conventional pattern on the storage layer with low coercivity using a conventional magnetic transducer. Then, a method has been proposed in which a narrow portion thereof is recorded by a conventional thermomagnetic transfer process using a laser light source for a main storage layer having a high coercive force. In this method, information is read out by transferring the information from the main storage layer to the storage transmission layer and using a conventional magnetic transducer.

In Japanese Patent Application Laid-Open No. 63-276731, information is recorded on a disk having a two-layer structure of a Co-Cr alloy thin film and a Tb-Fe thin film by using a magnetic head and transferring the information using an optical head. It has been proposed that information be reproduced using an optical head.

If such a method is used, unerased portions are reduced, and pit length recording becomes easy.

[Problems to be solved by the invention]

However, the method using the medium having the two-layer structure has a problem that information transfer stability is poor.

An object of the present invention is to solve such a conventional problem,
An object of the present invention is to provide an information recording method capable of stably overwriting.

[Means for solving the problem]

The object is to provide a first magnetic layer having a compensation temperature between room temperature and the Curie temperature, and a second magnetic layer having a Curie temperature lower than the compensation temperature of the first magnetic layer and a high coercive force at room temperature. Using a laminated recording medium, firstly, a modulation magnetic field is applied to the first magnetic layer by a magnetic head to record information, and then the medium is irradiated with a light beam to determine the Curie temperature of the first magnetic layer and the second magnetic layer. This is achieved by an information recording method in which information recorded on the first magnetic layer is transferred to the second magnetic layer by raising the temperature to a temperature between the Curie temperatures of the layers.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram for explaining an embodiment of the present invention. In FIG. 1, 1 is a perpendicular magnetic head, 2 is an objective lens in an optical head, 3 is a magneto-optical disk, 4 is a substrate, 5 is a protection and interference layer, 6 is a recording magnetic layer, 7 is a recording auxiliary magnetic layer. Layer 8 is a protective layer. FIG. 2 shows the characteristics of the coercive force with respect to the temperature of these magnetic layers. Curve 9 is
The characteristics of the recording assisting magnetic layer 7 are shown. That recording auxiliary magnetic layer 7 is small coercive force H _c1 at room temperature, also those with a high Kiyuri temperature T _c1. On the other hand, curve 10 shows the characteristic of the recording magnetic layer 6, large coercive force H _c2 at room temperature than the recording auxiliary layer 7, lower Curie temperature T _c2
It has. Further, T _comp of the curve 9 indicates the magnetic layer 7
Is the compensation point temperature.

It is assumed that the magneto-optical disk having such a configuration is moving in the direction of arrow A as shown in FIG. The light spot by the light head enters from the substrate side. The diameter of the light spot on the magnetic layer is about 1 μm. A servo system for scanning a desired track with the light spot can be performed by a conventionally well-known method.

On the other hand, the perpendicular magnetic head 1 is closely floating on the side opposite to the substrate side, and on a track scanned by an optical spot,
It is located slightly ahead of the light spot. The distance between these heads must be at least as large as the range affected by the heat from the optical spot and the range affected by the magnetic field from the perpendicular magnetic head do not overlap. The tracking of the perpendicular magnetic head is performed in accordance with the tracking of the optical head.

Next, a method for recording information will be described with reference to FIGS. 3A and 4A, FIG. 3A is a schematic sectional view of a magneto-optical disk, and FIG. 3B is a plan view. In FIG. 3A, a magnetic field is modulated in accordance with recorded information by using a perpendicular magnetic head 1. At this time, the maximum magnitude of the absolute value of the magnetic field on the magnetic layer depends on the recording auxiliary magnetic layer (hereinafter, referred to as an auxiliary layer) 7 and the recording magnetic layer (hereinafter, referred to as a recording layer) 6 at room temperature. Retention force H _c1 and H _c2
When a proper value is set between the above, the pits are formed as vertical magnetic domain arrays due to the difference between the upward and downward directions in the auxiliary layer 7 according to the modulation of the magnetic field. However, the recording layer 6
In (2), the intensity of the applied magnetic field is equal to or lower than the coercive force, so that the previous state is maintained without being affected.

The length in the direction parallel to the track of the pit by the perpendicular magnetic head can be on the order of submicron,
The linear density can be increased as compared with the conventional pit recorded by the optical head. Further, the width in the direction perpendicular to the track is set to several to several tens of tracks, so that the tracking accuracy required for the perpendicular magnetic head can be relaxed.

In FIG. 3 (b), reference numerals 11a to 11e denote tracks, respectively, each having a width of 1 to 2 μm. The pit recorded by the perpendicular magnetic head has a magnetic domain sequence shown by a solid line. Assuming that the track to be recorded is 11, the magnetic domain sequence is overwritten on the previous data over several to several tens of tracks around the center 11c.

After recording the magnetic domain sequence with the perpendicular magnetic head 1 in this manner,
As shown in FIG. 4, the spot 12 of the optical head 2 scans on a desired track 11c. The elevated temperature of the magnetic layer at this time, so that the appropriate temperature between each Kiyuri temperature T _c1 and T _c2 of the auxiliary layer 7 and the recording layer 6, and controls the light intensity according to disc rotation speed . Then light spot 12
The recording layer 6 Serra Atsu' above Kiyuri temperature T _c2
In the desired track 11c, the previously recorded information is erased by the disappearance of the magnetization. The passed light Supotsuto and Kiyuri temperature T _c2 less heat drops, magnetization appears corresponding to the magnetization of the auxiliary layer 7. That is, the auxiliary layer 7 is provided in the hatched area of the recording layer 6 in FIG.
Are transferred and information is written.

Here, as described above, the auxiliary layer 7 has a compensation point at room temperature or higher, and has a large coercive force at the temperature during transfer, so that stable transfer is performed.

The final pit shape recorded in this way is approximately square. The length of the pit in the direction parallel to the track has a submicron size determined by the perpendicular magnetic head, and the width in the direction perpendicular to the track is about 1 μm determined by the light spot of the light head.

On the other hand, reproduction of information by light Supotsuto optical head to scan the desired track, as the temperature of the magnetic layer is lower than the Kiyuri point temperature T _c2 of the second layer, the perpendicular magnetization of a desired track of the recording layer Is detected as the difference in the polarization state of the reflected light by the magneto-optical effect such as the Kerr effect, the Faraday effect, and the circular dichroism effect.

Also shown in Figure 2, the temperature of the intersection point of the curve 9 and 10 T _w0
Then, the temperature of the magnetic layer at the time of recording is set between T _w0 and T _c1 ,
The temperature of the magnetic layer during reproduction may be set to _Tw0 or less.

The power of the semiconductor laser for recording / reproducing in this method may be binary.

Further, the recording on the auxiliary layer by the magnetic head may be performed by overwriting as described above, or in order to remove the unerased data, the image is transferred by an optical spot, and then the same magnetic head or the second magnetic head is used. You may delete it.

5 and 6 show other examples of the configuration of the magneto-optical disk used in the present invention, respectively, and FIG. 7 shows the characteristics of the coercive force of each layer with respect to the temperature in these disks.

FIG. 5 shows an arrangement in which an exchange force adjusting layer 34 is arranged between the auxiliary layer 7 and the main recording layer 6 of the configuration of the magneto-optical disk shown in FIG. The coercive force H _c3 at room temperature and the Curie temperature T _c3 of this layer are
The characteristics are as shown by a curve 36 in FIG. This layer
At room temperature, it is magnetized in the in-plane direction, and when the temperature rises by the power of the optical spot at the time of recording, the auxiliary layer 7 has the same perpendicular magnetization as the direction of magnetization or disappears. Then, it functions to weaken the exchange coupling force between the auxiliary layer 7 and the main recording layer 6 at room temperature. Therefore, the strength of the magnetic field during recording can be further reduced to _Hc1 .

In FIG. 6, a reproducing layer 35 is further provided between the recording layer 6 and the protection / interference layer 5 having the structure shown in FIG. As described above, the Kerr rotation angle due to the Kerr effect at the time of reproduction is larger in the magnetic layer having a higher Curie temperature. Therefore, the coercive force H _c4 and Kiyuri temperature T _c4 of the reproducing layer 35 has a characteristic such as curve 37 of Figure 7. This reproduction layer 35
At a temperature increased by the power of the optical spot during reproduction, a perpendicular magnetization corresponding to the magnetization of the pit of the recording layer 6 appears due to the exchange coupling force with the recording layer 6. Since the reflection of light at the time of reproduction is almost influenced by the reproduction layer 35, the Kerr rotation angle is larger than that at the time of reflection at the recording layer 6.

Up to here, as shown in FIG. 2, the characteristics of the auxiliary layer 7 and the recording layer 6 have a compensation point at room temperature or higher (curve 9), and the recording layer 6 has no compensation point (curve 10). Although the case has been described, the configuration shown in FIG. 5 or FIG. 6 may have the characteristics shown in FIG. 8 to FIG. Here, FIGS. 8, 9 and 10 show the auxiliary layer 7 respectively.
(Curve 9 ') and the main recording layer 6 (Curve 10) have no compensation point, while the auxiliary layer 7 (Curve 9') has no compensation point.
The recording layer 6 (curve 10 ') has a compensation point, and the auxiliary layer 7 (curve 9) and the recording layer 6 (curve 10') also have compensation points.

As a specific material for each layer of the magnetic layer group, an amorphous alloy made of a combination of at least one of a transition metal and a rare earth metal can be used. For example, as a transition metal,
Mainly Fe, Co, Ni, and rare earth metals are mainly Gd, Tb, Dy, Ho, N
There are d and Sm. Typical combinations are TbFeCo, GdTbF
e, GdFeCo, GdTbFeCo, GdDyFeCo and the like.

The material of the auxiliary layer is Co-Cr, Ba-Ferrite, MnBi.
System, iron oxide system, Co-doped iron oxide system, CrO ₂ system, Ni-Co system, Fe-N
A magnetic material such as an i-Co system or a Heusler alloy such as PtMnSb may be used. The auxiliary layer 7 may be a magnetic layer having in-plane magnetization as shown in FIG. In this case, an in-plane magnetic head is used for recording.

The substrate 4 is a plastic material such as a glass material, polycarbonate (PC), or polymethyl methacrylate (PMMA), and may be thick and hard, or may be thin and flexible.

The present invention can be applied to various applications in addition to the embodiments described above. For example, although a magneto-optical disk has been described in the embodiments, a card-shaped or tape-shaped medium may be used.

Further, the magnetic head and the optical head are not limited to the configuration arranged on the opposite side as described in the embodiment. For example, in FIG. 1, the optical head is provided with respect to the magnetic head and the record carrier. May be on the same side. In such an arrangement, the arrangement of the recording layer 6 and the auxiliary layer 7 may be the same as in FIG. 1, or the two layers may be upside down.

〔The invention's effect〕

As described above, the information recording method of the present invention enables more stable overwriting.

[Brief description of the drawings]

FIG. 1 is a schematic view for explaining an embodiment of the present invention, FIG. 2 is a view showing characteristics of a magneto-optical disk used in the present invention, and FIGS. 3 and 4 are recording and transfer processes according to the present invention, respectively. FIGS. 5 and 6 are schematic cross-sectional views showing another example of the configuration of a magneto-optical disc used in the present invention, and FIGS. 7 to 10 are magneto-optical discs used in the present invention, respectively. FIG. 11 is a schematic diagram showing the state of magnetization when an in-plane magnetic film is used for the auxiliary layer. DESCRIPTION OF SYMBOLS 1 ... Magnetic head, 2 ... Optical head, 3 ... Magneto-optical disk, 4 ... Substrate, 5 ... Protection and interference layer, 6 ... Recording layer, 7 ... Auxiliary layer, 8 ... Protective layer.

Continuation of the front page (72) Inventor Yutaka Ogasawara 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Makoto Hiramatsu 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-63-276731 (JP, A) JP-A-63-155449 (JP, A)

Claims (1)

(57) [Claims] 1. A first magnetic layer having a compensation temperature between room temperature and the Curie temperature, and a second magnetic layer having a Curie temperature lower than the compensation temperature of the first magnetic layer and a high coercive force at room temperature.
Using a recording medium formed by laminating magnetic layers, firstly, a modulation magnetic field is applied to the first magnetic layer by a magnetic head to record information, and then the medium is irradiated with a light beam to determine the Curie temperature of the first magnetic layer and the first temperature. An information recording method in which information recorded in the first magnetic layer is transferred to the second magnetic layer by raising the temperature to a temperature between the Curie temperatures of the second magnetic layer.