JPH0540975A - Magneto-optcal recording method - Google Patents

Abstract

(57) [Summary] [Structure] While applying an external magnetic field Hex of a certain magnitude to the magneto-optical recording medium layer 2, a light beam whose intensity is modulated according to information is irradiated to produce a strong optical intensity. When, the direction of magnetization of the perpendicular magnetization film in the area irradiated with the light beam is directed toward the direction of the external magnetic field or the magnetization of the bias magnetic layer, and when the light intensity is weak, Information is rewritten by orienting the direction of magnetization of the perpendicular magnetization film in the direction of the demagnetizing field generated by the magnetization of the region around the region. [Effect] Overwriting by optical modulation recording can be realized without using an initialization magnet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of overwriting a magneto-optical memory device such as a magneto-optical disk by optical modulation recording.

[0002]

2. Description of the Related Art In recent years, a magneto-optical memory device such as a magneto-optical disk has attracted attention as a high-density and large-capacity memory device capable of rewriting information. Above all, the need for a so-called overwriting magneto-optical memory element that does not require erasing information when rewriting information is increasing year by year.

Magnetic field modulation recording and optical modulation recording using an exchange coupling film are considered as the overwriting method.

In overwrite by magnetic field modulation recording,
Information is recorded by irradiating a predetermined recording area of the magneto-optical memory device with a constant intensity of a light beam while applying a magnetic field which is reversed in accordance with the recording information from the magnetic head to the recording area. As this magnetic head, a levitation type magnetic head equipped with a slider employed in a hard disk drive or the like is used so as to generate a high-frequency strong magnetic field.

Overwrite by light modulation recording is 1
Exchange of a two-layer structure in which a memory layer made of a magnetic material and an auxiliary layer are laminated on a glass substrate, as described in 1987, Spring Meeting of the Japan Society of Applied Physics, page 721, Lecture No. 28p-ZL-3. A magneto-optical memory element composed of a coupling film is used. When overwriting is performed, first, the magnetization of the auxiliary layer is aligned in one direction by the initialization magnet. Then, while applying a magnetic field to the predetermined recording area of the memory layer in the direction opposite to the above-mentioned direction by the auxiliary magnet, by irradiating the recording area with a light beam whose light intensity changes strongly depending on the information, Is recorded.

[0006] In addition, the 13th Japan Society for Applied Magnetic Science Academic Lectures (1989), page 192, Lecture No. 28p-
The ZL-3 uses a magneto-optical memory element including an exchange coupling film having a four-layer structure in which an initialization layer made of a magnetic material, a control layer, a recording auxiliary layer, and an information recording layer are laminated on a glass substrate. .. The magnetization of the initialization layer is aligned in one direction in advance and is not reversed during operation. In the case of overwriting, while applying a magnetic field in a direction opposite to the above direction to a predetermined recording area of the information recording layer by an auxiliary magnet, the recording area is irradiated with a light beam whose light intensity changes depending on information. By doing so, the information is recorded.

[0007]

However, in the overwrite by the magnetic field modulation recording described above, when the magnetic head starts to fly, the slider equipped with the magnetic head slides on the magneto-optical memory element, and therefore, the magneto-optical memory. There are problems that the element may be scratched and the magnetic head may crash. That is, the non-contact recording / reproducing of information, which is a major feature of the magneto-optical memory device, is sacrificed.

Further, in overwriting by optical modulation recording using a magneto-optical memory element composed of a double-layered exchange coupling film, a large initialization magnet which generates a magnetic field of several kOe is required for initialization. There is a problem of doing.

In overwriting by optical modulation recording using a magneto-optical memory element consisting of an exchange coupling film having a four-layer structure, if the initialization layer is initialized in advance, thereafter,
Although it is not necessary to newly initialize it, there is a problem that it is difficult to control the coercive force and the Curie temperature of each layer to predetermined values during manufacturing.

[0010]

According to another aspect of the present invention, there is provided a magneto-optical recording method, wherein a perpendicular magnetic film for recording information is formed on a substrate, and the magneto-optical memory element is driven in a predetermined direction. While applying an external magnetic field of the magnitude of to the perpendicular magnetization film in the perpendicular direction, a light beam whose light intensity is modulated according to information is irradiated. When the light intensity is strong, the light beam is irradiated. The direction of the magnetization of the perpendicular magnetization film in the area where the light beam is irradiated is changed to the direction of the external magnetic field, and the direction of the magnetization of the perpendicular magnetization film in the area irradiated with the light beam is the area surrounding the area. The information is rewritten by directing it in the direction of the demagnetizing field opposite to the direction of the external magnetic field generated by the magnetization of.

A magneto-optical recording method according to the invention of claim 2
A perpendicular magnetic film for recording information on a substrate and a bias magnetic film whose magnetization is aligned in a direction perpendicular to the film surface of the perpendicular magnetic film are formed, and a magneto-optical memory device driven in a predetermined direction, A light beam whose light intensity is modulated according to information is irradiated. When the light intensity is strong, the direction of magnetization of the perpendicular magnetization film in the region irradiated with the light beam is determined by the direction of magnetization of the bias magnetic film. When the intensity of the light is weak, the direction of magnetization of the perpendicular magnetization film in the region irradiated with the light beam is determined by the direction of magnetization of the bias magnetic film generated by the magnetization of the region surrounding the region. Is characterized by rewriting information by directing it in the opposite direction of the demagnetizing field.

[0012]

According to the structure of claim 1, when the magneto-optical memory element in which the perpendicularly magnetized film is formed on the substrate is used, when the light intensity of the light beam is high, the perpendicularly magnetized film irradiated with the light beam is Since the coercive force of the region decreases with increasing temperature, the magnetization is oriented in the direction of the external magnetic field. On the other hand, when the light intensity of the light beam is weak, the magnetization of the region of the perpendicular magnetization film irradiated with the light beam increases due to the temperature decrease. The interaction with the demagnetizing field, which is opposite to the direction of the external magnetic field generated by the magnetization of, increases, and the direction of the demagnetizing field is increased. As a result, overwriting by optical modulation recording can be realized without using an initialization magnet.

According to the structure of claim 2, a magneto-optical memory element is used, in which a perpendicular magnetic film and a bias magnetic film whose magnetization is aligned in a direction perpendicular to the film surface of the perpendicular magnetic film are formed on a substrate. Therefore, since the bias magnetic film has a function similar to that of the external magnetic field according to the first aspect, overwriting by optical modulation recording can be realized without applying an external magnetic field.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following will describe one embodiment of the present invention with reference to FIGS.

As shown in FIG. 3, a magneto-optical disk as a magneto-optical memory element used in this embodiment has a structure in which a magneto-optical recording medium layer 2 is provided on a disc-shaped optically transparent substrate 1. It has become. Usually, a guide track for guiding the light beam 5 is formed on the magneto-optical recording medium layer 2 side of the substrate 1.

The magneto-optical recording medium layer 2 has, for example, a three-layer structure in which a first dielectric film, a perpendicular magnetization film made of a magnetic material, and a second dielectric film are sequentially laminated from the substrate 1 side. There is. The first and second dielectric films serve to protect the perpendicular magnetization film. Further, the first dielectric film also functions to emphasize the magnetic Kerr effect. A four-layer reflective film structure in which a reflective film is further provided on the second dielectric film may be used.

A magneto-optical disk having a magneto-optical recording medium layer 2 having a three-layer structure is concretely, for example, a substrate 1 made of polycarbonate and AlN 8 as a first dielectric film.
0 nm, Dy ₂₀ Fe ₅₆ Co ₂₄ is 100 as a perpendicular magnetization film.
nm, and AlN having a thickness of 80 nm as the second dielectric film are sequentially formed. The perpendicular magnetic film had a coercive force at room temperature of 5 kOe and a Curie temperature of 200 ° C.

Further, the magneto-optical disk having the magneto-optical recording medium layer 2 of the four-layer reflective film structure is specifically, for example, AlN as the first dielectric film having a thickness of 80 nm and perpendicular to the substrate 1 made of polycarbonate. Dy ₂₀ Fe ₅₆ C as a magnetic film
o ₂₄ is 20 nm and AlN is 25 n as the second dielectric film.
m and Al as a reflective film having a thickness of 50 nm are sequentially formed.

A magneto-optical disk device as a magneto-optical recording / reproducing apparatus used in this embodiment basically has an optical head 3 arranged on the substrate 1 side of the magneto-optical disk and a magneto-optical disk. It is composed of an electromagnet 6 arranged on the recording medium layer 2 side so as to face the optical head 3.

The optical head 3 has a light source such as a semiconductor laser, and is provided with an objective lens 4 for converging light emitted from the light source and irradiating the magneto-optical recording medium layer 2 with a light beam 5.

The electromagnet 6 is composed of a cylindrical magnetic core 7 and a coil 8 wound around the magnetic core 7, and has a certain size on the magneto-optical recording medium layer 2 irradiated with the light beam 5. The external magnetic field Hex can be applied in the direction perpendicular to the magneto-optical recording medium layer 2.

In the above structure, when overwriting, that is, rewriting information by overwriting, the electromagnet 6 is attached to the magneto-optical disk which is rotationally driven in a predetermined direction.
A more constant external magnetic field Hex is applied to the magneto-optical recording medium layer 2
While being applied in the vertical direction (downward), a light beam 5 whose intensity is modulated according to information is emitted.

The overwrite operation when the light intensity of the light beam 5 is changed as shown in FIG. 1A will be described. Here, the vertical axis represents the light intensity and the horizontal axis represents time.

The state of magnetization of the perpendicular magnetization film in the magneto-optical recording medium layer 2 when the light intensity of the light beam 5 is changed as shown in (a) is shown in (b) of the same figure. The direction of magnetization is indicated by an upward or downward arrow. Further, the position of the magneto-optical recording medium layer 2 in the track direction and the light intensity of the light beam 5 with which the position is irradiated correspond to each other.

The light intensity of the light beam 5 is the erasing power level P.
When it is at _E (high level), the magnetization direction of the perpendicular magnetization film is the direction of the external magnetic field Hex, that is, the downward direction. On the other hand, when the light intensity of the light beam 5 is set to zero (low level), the direction of the magnetization becomes the direction of the demagnetizing field generated by the downward magnetization (shown by the broken line), that is, the upward direction. ..

FIG. 2 shows the above overwrite operation.
Based on, it will be described in more detail as follows.

Consider a case where the light intensity of the light beam 5 is changed as shown in FIG. The light intensity of the light beam 5 is initially
At erase power level P _E (high level), time t ₂
It is assumed that the recording power level P _L (low level) is dropped to and the erasing power level P _E is returned to at the time t ₃ . In addition,
The erasing power level P _E is the laser power that can raise the perpendicular magnetization film to the Curie temperature or higher, and the recording power level P _L is the laser power that cannot raise the perpendicular magnetization film to the Curie temperature, which is usually zero. ..

The states of magnetization of the perpendicularly magnetized film in the magneto-optical recording medium layer 2 when the light intensity of the light beam 5 is thus changed are shown in (b) to (f) of FIG. The direction of magnetization is indicated by an upward or downward arrow, and the position of the magneto-optical recording medium layer 2 in the track direction corresponds to the light intensity of the light beam 5 irradiated at that position. Is illustrated in.

At time t ₁ , since the light intensity of the light beam 5 is at the erasing power level P _E , the region 11 of the perpendicularly magnetized film irradiated with the light beam 5 is heated to the Curie temperature or higher (hatched line). Indicates that the temperature is above the Curie temperature). Therefore, the magnetization of the region 11 has disappeared. The regions 12 and 12 on both sides of the region 11 have magnetization because they are lower than the Curie temperature, but their sizes are small because they are high temperature. The direction of magnetization of the region 12 is the direction of the demagnetizing field (indicated by the broken line) generated by the magnetization of the region 13 outside the region 12 (direction of the external magnetic field Hex, that is, downward), that is, the external magnetic field. It is facing up, which is opposite to the direction of Hex.

Since the light intensity of the light beam 5 is at the erasing power level P _E until the time t ₂ , the region 1 heated to the Curie temperature or higher as the magneto-optical disk rotates.
1 moves to the right as in (c), and the region 13 having downward magnetization also spreads to the right with this movement. This is because when the light intensity of the light beam 5 is at the erasing power level P _E , the direction of magnetization is aligned with the direction of the external magnetic field Hex.

When the light intensity of the light beam 5 is lowered to the recording power level P _L at the time t ₂ , the temperature of the regions 11 and 12 drops sharply. As a result, the magnetization of the region 12 is increased, so that the interaction with the demagnetizing field generated by the magnetization of the region 13 is increased. For this reason, the region 12 having the upward magnetization increases, and as shown in FIG.
12a is formed. In addition, the region 1 having downward magnetization due to the demagnetizing field generated by the upward magnetization of the region 12a.
4 is formed.

When the light intensity of the light beam 5 is again raised to the erasing power level P _E at time t ₃ , the region 11 irradiated with the light beam 5 is heated to the Curie temperature or higher as shown in (e). The magnetization of this region 11 disappears. Also,
Along with this, the area 14 also decreases to become the area 14b.

At time t ₄ , the region 11 heated to the Curie temperature or higher moves to the right as shown in (f), and with this movement, the region 14b having downward magnetization spreads to the right and extends to the region 14a. become. This is because, as described above, when the light intensity of the light beam 5 is at the erasing power level P _E , the direction of magnetization is aligned with the direction of the external magnetic field Hex.

As described above, the recording power level P _L
By irradiating the light beam 5 with, the region 12a having upward magnetization in the direction opposite to the external magnetic field Hex can be formed in the perpendicular magnetization film of the magneto-optical recording medium layer 2.

An overwrite test was actually conducted using the two types of magneto-optical disks shown in the above specific examples. As test conditions, the rotation speed of the magneto-optical disk was 900 rpm, the erasing power level P _E was 7 mW, the recording power level P _L was 0 mW, and the external magnetic field Hex was 150 Oe.
The recording site was set at a position with a radius of 30 mm on the magneto-optical disk.

Under this condition, first, when the light beam 5 having the erasing power level P _E was irradiated for a period of 200 ns at a cycle of 1000 ns, the magneto-optical disk was about 2.8.
It was possible to form a recording bit having a length of 0.5 μm at intervals of μm.

Thereafter, 200 ns at a cycle of 1500 ns
When the light beam 5 having the erasing power level P _E is irradiated for the period of, the recording bits are erased, and recording bits having a length of 0.5 μm are newly formed on the magneto-optical disk at intervals of about 4.2 μm. We were able to.

Another embodiment of the present invention will be described below. For convenience of explanation, members having the same functions as those of the members shown in the drawings of the above-described embodiments are designated by the same reference numerals, and the description thereof will be omitted.

The magneto-optical disk as the magneto-optical memory element used in this embodiment has the above-mentioned embodiment in that an exchange coupling magnetic film having a two-layer structure is used for the magneto-optical recording medium layer 2 (FIG. 3). It differs from the example.

That is, the magneto-optical recording medium layer 2 of this embodiment
Has a structure in which, for example, an exchange coupling magnetic film including a first dielectric film, a perpendicular magnetization film and a bias magnetic film, and a second dielectric film are sequentially laminated from the substrate 1 side. The magnetization of the bias magnetic film is preliminarily aligned in the direction perpendicular to the perpendicular magnetic film, and the magnetization does not disappear even when the Curie temperature of the perpendicular magnetic film is reached. Therefore, the magnetization of the bias magnetic film has almost the same function as that of the electromagnet 6 of the above-described embodiment with respect to the perpendicular magnetization film. Therefore, the magneto-optical disk device of this embodiment has a configuration in which the electromagnet 6 of the above embodiment is omitted.

The magneto-optical disk having the magneto-optical recording medium layer 2 including the exchange coupling magnetic film is specifically, for example,
On the substrate 1 made of polycarbonate, AlN is 80 nm as the first dielectric film and Dy ₂₄ Fe is the perpendicular magnetization film.
₇₁ Co ₅ 50 nm, Gd ₁₂ Tb as bias magnetic film
It is obtained by sequentially forming ₁₂ Co ₇₆ of 100 nm and AlN of 100 nm as the second dielectric film. The perpendicular magnetic film had a coercive force at room temperature of 15 kOe or higher and a Curie temperature of 190 ° C., and the bias magnetic film had a coercive force at room temperature of 1.7 kOe and a Curie temperature of 300 ° C. or higher.

When an overwrite test was actually performed using the magneto-optical disk shown in the above specific example,
The same recording bit length as in the above example was obtained. The test conditions are the same as in the above embodiment. However, it is not necessary to apply the external magnetic field Hex by the electromagnet 6 as described above.

In the above embodiment, the period during which the light intensity of the light beam 5 is at the recording power level P _L is 0.1 to 1.
It is preferable to correspond to a period in which a recording bit length of 0 μm is obtained.

As an example of the magneto-optical memory element,
Although a magneto-optical disk has been described as an example, it can be applied to a magneto-optical card, a magneto-optical tape, and the like.

[0045]

As described above, in the magneto-optical recording method according to the invention of claim 1, the perpendicular magnetic film for recording information is formed on the substrate, and the magneto-optical memory element is driven in a predetermined direction, While applying an external magnetic field of a certain magnitude to the perpendicular magnetization film in the perpendicular direction, a light beam whose light intensity is modulated according to information is irradiated, and when the light intensity is strong, the light beam is irradiated. The direction of the magnetization of the perpendicular magnetization film in the region being irradiated is directed toward the direction of the external magnetic field, and when the light intensity is weak, the direction of the magnetization of the perpendicular magnetization film in the region irradiated with the light beam is Information is rewritten by directing the diamagnetic field in the direction opposite to the direction of the external magnetic field generated by the magnetization of the region.

As a result, there is an effect that overwriting by optical modulation recording can be realized only by applying an external magnetic field without using an initialization magnet.

A magneto-optical recording method according to the invention of claim 2
As described above, the perpendicular magnetic film for recording information on the substrate and the bias magnetic film whose magnetization is aligned in the direction perpendicular to the film surface of the perpendicular magnetic film are formed, and the light is driven in the predetermined direction. A magnetic memory element is irradiated with a light beam whose light intensity is modulated depending on information, and when the light intensity is strong, the direction of magnetization of the perpendicular magnetization film in the region irradiated with the light beam is changed to that of the bias magnetic film. When the light intensity is weak, the direction of magnetization of the perpendicular magnetic film in the region irradiated by the light beam is changed from the magnetization of the region surrounding the region when the light intensity is weak. The information is rewritten by directing it in the direction of the demagnetizing field opposite to the direction determined by the direction.

As a result, it is possible to realize the overwrite by the optical modulation recording without using the initialization magnet and without applying the external magnetic field.

[Brief description of drawings]

FIG. 1 is an explanatory view showing the basics of a magneto-optical recording method of the present invention, (a) shows a time change of light intensity of a light beam, and (b) shows a state of magnetization of a perpendicular magnetization film. ing.

FIG. 2 is an explanatory diagram showing details of a magneto-optical recording method,
(A) shows the time change of the light intensity of the light beam,
(B) to (f) show the state of magnetization of the perpendicularly magnetized film over time.

FIG. 3 is a schematic configuration diagram of a magneto-optical disk device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 substrate 2 magneto-optical recording medium layer 5 light beam 6 electromagnet 11 area 12 area 12a area 13 area 14 area 14a area 14b area

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenji Ota 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation

Claims (2)

[Claims] 1. A perpendicular magnetic film for recording information is formed on a substrate, and an external magnetic field of a constant magnitude is applied in a direction perpendicular to the perpendicular magnetic film to a magneto-optical memory device driven in a predetermined direction. While applying, a light beam whose intensity is modulated according to the information is irradiated, and when the light intensity is strong, the direction of magnetization of the perpendicular magnetization film in the region irradiated with the light beam is changed to the direction of the external magnetic field. When the light intensity is weak, the direction of the demagnetizing field which is opposite to the direction of the external magnetic field generated by the magnetization of the region around the region where the light beam is irradiated is the direction of the magnetization of the perpendicular magnetization film. A magneto-optical recording method characterized in that rewriting of information is carried out by making it suitable for recording. 2. A light which is driven in a predetermined direction, on which a perpendicular magnetic film for recording information and a bias magnetic film whose magnetization is aligned in a direction perpendicular to a film surface of the perpendicular magnetic film are formed on a substrate. A magnetic memory element is irradiated with a light beam whose light intensity is modulated depending on information, and when the light intensity is strong, the direction of magnetization of the perpendicular magnetization film in the region irradiated with the light beam is changed to that of the bias magnetic film. Orient it in the direction determined by the direction of magnetization,
When the light intensity is weak, the direction of magnetization of the perpendicular magnetization film in the region irradiated with the light beam is opposite to the direction determined by the direction of magnetization of the bias magnetic film generated by the magnetization of the region surrounding the region. A magneto-optical recording method characterized by rewriting information by directing it in the direction of a magnetic field.