JPH0562269A - Magneto-optical recording system - Google Patents

Abstract

PURPOSE:To provide a magneto-optical recording system capable of overwriting at high speed by a simple device constitution by using a magneto-optical recording medium using the single layer of a vertical magnetized film as a recording layer. CONSTITUTION:By impressing plural pieces of a laser pulse at the time of forming a magnetic domain and erasing the magnetic domain respectively, the required length of the magnetic domain is formed or erased. On a method for impressing the laser pulse, one kind of the laser pulse is impressed at the time of forming the magnetic domain and erasing the magnetic domain respectively, or combined two kinds of the laser pulse is impressed. At this time, the intensity and the pulse width of the impressed laser pulse are made so as to be satisfied with a prescribed relation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording system which uses a magneto-optical recording medium having a single-layered perpendicularly magnetized film as a recording layer and performs high-speed overwriting by utilizing a demagnetizing field.

[0002]

2. Description of the Related Art In recent years, as a rewritable optical recording medium, a magneto-optical recording medium utilizing a magneto-optical effect has been vigorously researched and developed, and has been partially put into practical use. This magneto-optical recording medium has the advantages of large-capacity and high-density recording, non-contact recording / playback, ease of access, etc., and can be used for document information files, video / still image files, computer memory, etc. Are seen as promising. In order to make a magneto-optical recording medium a recording medium having a performance equal to or higher than that of a magnetic disk, there are some technical problems, and one of the main ones is an overwrite technique.

In the magneto-optical recording medium currently on the market, it is necessary to erase the original information in advance to rewrite the information and then write new information.
This erasing operation is a time loss. Overwriting technology eliminates this drawback. The overwrite technology proposed so far is roughly classified into a magnetic field modulation method and an optical modulation method (multi-beam method, two-layer film method, etc.) depending on the recording method.

The magnetic field modulation system is a system in which the intensity of light is kept constant and the polarity of the applied magnetic field is reversed according to the recorded information for recording. In this method, in order to perform the reversal of the magnetic field at a high speed, measures such as using a flying type magnetic head have been studied, but there is a problem that medium replacement becomes difficult. Only the surface can be used,
There is a problem that the memory capacity is halved.

On the other hand, the optical modulation system is a system in which the applied magnetic field is kept constant and the irradiation laser beam is turned on / off or intensity modulated according to the recording information to perform recording. Among the optical modulation methods, the multi-beam method is a pseudo-overwrite method that uses 2-3 laser beams and reverses the direction of the magnetic field each time the magneto-optical recording medium makes one revolution, to perform recording / erasing. It has drawbacks such as a complicated device configuration and increased cost. The two-layer film system is a system in which the recording layer of the magneto-optical recording medium is a two-layer film to achieve overwriting, and is disclosed in, for example, Japanese Patent Laid-Open No. 62-175948. The method described in the publication is, for example, T
A magneto-optical recording medium having a recording layer made of bFe and an auxiliary layer made of TbFeCo is used, and after initialization, an attempt is made to realize overwriting by applying an external magnetic field and irradiating a laser beam having a different power. It is a thing.
That is, in this method, prior to recording, the magnetization of the auxiliary layer is aligned in one direction with an initializing magnetic field of about 4 KOe.
Irradiate a high power laser beam to change the medium temperature T to T> Tc
₂ (Tc ₂ is the Curie temperature of the auxiliary layer), a recording magnetic field (in the direction opposite to the initialization magnetic field) is applied to reverse the magnetization of the auxiliary layer, and when the medium is cooled, Recording is performed by transferring the magnetization to the memory layer, and the medium temperature is changed to Tc ₁ by irradiating a low power laser beam.
Erasure is performed by increasing the temperature to <T <Tc ₂ (Tc ₁ is the Curie temperature of the recording layer) and transferring the magnetization direction of the auxiliary layer to the memory layer. However, although this method is advantageous in terms of high speed, it has a problem that the laser power during writing is high and that a very large magnetic field must be applied in the initialization process performed before overwriting. ..

As described above, several methods have been proposed as an overwrite method for magneto-optical recording, but each of them has not only advantages but also disadvantages. It is said that breakthroughs must be repeated.

On the other hand, an overwrite method using a demagnetizing field has been proposed (Han-Ping; Ap).
pl. Phys. Lett., 49, p8 (1986)). This method uses a magneto-optical recording medium having a recording layer having a compensation temperature several tens of degrees higher than room temperature, and overwrites without using an external magnetic field. The principle will be briefly described. Recording is performed by irradiating a position on the recording layer to be recorded with a first laser beam. By this laser beam irradiation, the irradiated portion is heated to a temperature higher than the compensation temperature Tcomp, and the magnetization of that portion is reversed, and at the same time, a demagnetizing field is generated in the opposite direction. Is formed. Then, a recording magnetic domain is formed in the cooling process after the irradiation is completed. Further, erasing is performed by irradiating a second laser beam directly above the recording magnetic domain. By this laser beam irradiation, the irradiated portion is heated to a temperature higher than the compensation temperature Tcomp, the magnetization in the recording magnetic domain is reversed, and at the same time, a demagnetizing field is generated in the opposite direction. The demagnetizing field inverts the magnetization of the central portion of the recording magnetic domain again to form the second domain wall, which disappears due to the domain wall movement. Then, the recording magnetic domains are erased in the cooling process after the irradiation. Although this method is a kind of optical modulation method, the recording medium used has a single-layer structure, and there is a high possibility that writing can be performed with lower power than a double-layer film recording medium, and a magnetic field for initialization is prepared. It is attracting attention because it is not necessary.

In this system, however, the previously recorded signal is detected prior to overwriting, and the signal is compared with a newly written signal to determine whether or not the laser beam irradiation is performed. Beam recording,
Even if two pieces are prepared for detection, or one laser beam also serves as recording detection, it is necessary to rotate twice per track. Furthermore, when laser beam irradiation is performed, it is necessary to strictly align with the previously written magnetic domain. Therefore, the function to read the signal previously written before the overwrite, the function to compare the signal with the signal to be newly written and determine whether or not to perform the laser beam irradiation, and the time before the laser beam irradiation is performed. The position adjustment function for irradiating the laser beam directly above the signal written in the device must be added to the device, which causes a problem that the device configuration becomes complicated. Further, this method has a drawback that it cannot be applied to the mark length modulation method.

Further, in Japanese Patent Laid-Open No. 1-119941, a single laser pulse is irradiated at the time of forming a magnetic domain, and a plurality of laser pulses having a width narrower than that at the time of recording is irradiated at the time of erasing the magnetic domain to overwrite. A method of doing so has been proposed. However, in this method, if an attempt is made to form the magnetic domain shown in FIG. 8B by the laser irradiation shown in FIG. 8A, the edge portion at the rear end of the magnetic domain is not fixed and the edge shown in FIG. As shown in the figure, a phenomenon that a cylindrical magnetic domain moves following a laser beam or a phenomenon that the magnetic domain shape of an edge portion is deformed as shown in FIG. It is very difficult to control by laser irradiation of a single pulse. Therefore, there is a problem that it is unsuitable for signal mark length modulation or mark edge recording.

An object of the present invention is to solve these problems in the prior art, and to provide a magneto-optical recording system capable of performing overwriting with a simple device configuration at high speed and with high reliability. And Further, the present invention is
An object of the present invention is to provide a magneto-optical recording method suitable for the mark length modulation method.

[0011]

In order to achieve the above object, according to the present invention, a magneto-optical recording medium having a single-layered perpendicular magnetization film as a recording layer is irradiated with a laser beam to form and erase magnetic domains. Is a magneto-optical recording method for controlling overwriting to perform overwritable magneto-optical recording, and forms or erases a magnetic domain to a desired length by applying a plurality of laser pulses each at the time of domain formation and domain erase. A magneto-optical recording method is provided.

In the above, a plurality of laser pulses of one kind each are irradiated at the time of forming the magnetic domain and at the time of erasing the magnetic domain, or
It is preferable to irradiate a plurality of combinations of two types of laser pulses each at the time of forming the magnetic domain and at the time of erasing the magnetic domain.

When a plurality of laser pulses of one kind are irradiated at the time of forming the magnetic domain and at the time of erasing the magnetic domain, the intensity of the laser pulse irradiated at the time of forming the magnetic domain is Pw and the pulse width is τw.
, Pe is the intensity of the laser pulse to be emitted when erasing the magnetic domain,
When the pulse width is τe, τw ≧ τe and Pw · τw
It is desirable to satisfy the relation of> Pe · τe.

Two kinds each when forming a magnetic domain and when forming a magnetic domain
When combining multiple laser pulses and irradiating multiple
Irradiate first during both magnetic domain formation and magnetic domain erasure
Laser pulse and laser pulse to be emitted after the second
It is desirable to have different types of laser pulses in
Of the laser pulse that is irradiated first when the magnetic domains are formed.
Strength is Pw₁, Pulse width τw₁, Irradiation after the second
Laser pulse intensity is Pw₂, Pulse width τw₂, Magnetic domain erase
P is the intensity of the first laser pulse emitted when leaving
e₁, Pulse width τe₁, The laser to be irradiated after the second
The intensity of the pulse is Pe₂, Pulse width τe₂And then Pw₁<Pe₁  Pw₁・ Τw₁＞ Pe₁・ Τe₁  Pw₂= Pe₂  τw₂= Τe₂  It is more desirable to satisfy the following relational expression at the same time.

[0015]

In the present invention, since a plurality of laser pulses are applied at the time of forming the magnetic domains, the cylindrical magnetic domains are formed by the first laser pulse irradiation, and the irradiation center is at a predetermined distance in the second laser pulse irradiation. Irradiation is performed at a position moved by a distance, and heat transfer due to the irradiation hardly contributes to the domain wall on the side far from the irradiation center of the cylindrical magnetic domain, and the domain wall in this portion is pinned. The same applies to the irradiation of the third and subsequent laser pulses, the magnetic domain edge portion is reliably fixed, and a magnetic domain of a desired length is easily formed. Further, by irradiating a plurality of laser pulses having a shape different from that at the time of magnetic domain formation at the time of magnetic domain erasing, the sum of the demagnetizing field energy, the domain wall energy and the Zeeman energy applied to the domain wall becomes lower than that at the time of domain contraction, so that Magnetic domains are erased over the length without erasing. Therefore, it becomes possible to write a new signal irrespective of the previously written signal, and moreover, high-speed and highly reliable overwrite can be realized with a simple device configuration.

[0016]

The method of the present invention will be described in detail below. According to the method of the present invention, a plurality of laser pulses are applied to a magneto-optical recording medium having a single layer of perpendicularly magnetized film as a recording layer, so that a magnetic domain having a desired length is irrespective of a previously written signal. And a plurality of laser pulses are similarly applied to erase magnetic domains over a desired length. A constant external magnetic field of several tens to several hundreds Oe is applied to the laser beam irradiation portion of the magneto-optical recording medium at the time of signal recording and erasing, but the external magnetic field may not be applied depending on the characteristics of the medium used.

The method of the present invention is roughly classified into the following two types according to the method of applying the laser pulse. (i) A method of irradiating a plurality of laser pulses of one kind each at the time of forming the magnetic domain and at the time of erasing the magnetic domain. (ii) A method of irradiating a plurality of laser pulses by combining two or more kinds of laser pulses each at the time of magnetic domain formation and at the time of magnetic domain erasure. Each method will be described in detail below.

First, the method (i) will be described. In carrying out this method, as a magneto-optical recording device, when applying a constant external magnetic field during signal recording (magnetic domain formation) and erasing (magnetic domain erasure), it is necessary to provide a magnetic field generation mechanism, which is conventionally required. It suffices to use the used permanent magnets, electromagnets, etc., and no initialization magnetic field or AC magnetic field is required. Regarding the laser output, as described above, a laser pulse having an intensity of Pw and Pe for irradiating the magneto-optical recording medium during signal recording and erasing, and a DC laser having an intensity Pr for irradiating the magneto-optical recording medium during signal reproduction are prepared. (However, Pr <Pw, Pr <Pe). In addition, there is no particular mechanism to be added to implement this method, and the magneto-optical recording device which has been conventionally used can be used only by making a simple improvement.

Next, the magneto-optical recording medium used in this system will be described. The magneto-optical recording medium used in this method uses a single-layered perpendicularly magnetized film as a recording layer, and its magnetic characteristics are such that a compensation temperature Tcomp is higher than room temperature Tr, that is, a so-called rare earth metal-rich composition. A rare earth metal-transition metal (RE-TM) amorphous magnetic film is preferably used. The layer structure of the magneto-optical recording medium is basically as shown in FIG.
As shown in FIG. 3, the RE-TM system amorphous magnetic film 2 having the above-mentioned magnetic characteristics is formed on the substrate 1 made of glass or plastic by the sputtering method or the like, and the magnetic film 2 is prevented from being degraded. Then, the protective film 3 is formed. Further, a base film may be sandwiched between the substrate 1 and the magnetic film 2 in order to improve the uniformity of the magnetic film and the characteristics of the reproduction signal. Further, in order to increase the storage capacity, it is possible to bond the media shown in FIG. 2 so as to record on both sides.

In this system, overwriting is achieved by using the device and medium having the extremely simple structure as described above, but particularly good overwriting is realized under the following conditions. That is, as shown in FIG. 1, at the time of forming a magnetic domain, that is, at the time of recording a signal, a laser pulse having an intensity Pw and a time τw is continuously irradiated several times until a magnetic domain having a desired length is obtained. A laser pulse having an intensity Pe and a pulse width τe is continuously irradiated several times until the erase magnetic domain has a desired length. However, Pw,
It is assumed that Pe and τw and τe satisfy the relations τe ≧ τw and Pw · τw> Pe · τe. In this method, by applying a plurality of laser pulses at the time of forming the magnetic domain, the magnetic domain edge portion is surely fixed and the magnetic domain having a desired length can be easily formed. The mechanism is explained as follows (FIG. 4). That is, a cylindrical magnetic domain (radius R) S is formed at the time of irradiating the first laser pulse of the laser pulses applied at the time of magnetic domain formation (however, if the magnetic domain already exists in the irradiation part before irradiation, The magnetic domain remains unchanged). After this irradiation, the second irradiation is performed with a certain time interval, and at that time, the irradiation center moves to a position displaced by a distance D from the center of the cylindrical magnetic domain. The heat transfer due to the irradiation is less likely to contribute to the domain wall w of the cylindrical magnetic domain farther from the irradiation center. Therefore, the domain wall w of this portion does not move by the second irradiation and is pinned in the initial state. After this, this state does not change even by the third and subsequent irradiations. That is, by performing pulsed laser irradiation, the magnetic domain edge portion is reliably fixed, and the magnetic domain edge portion having a desired length is easily formed. Further, by irradiating a plurality of laser pulses having a shape different from that at the time of domain formation at the time of domain erase, the sum of the demagnetizing field energy, domain wall energy, and Zeeman energy applied to the domain wall becomes lower when the domain contracts. Since it is possible to adjust the temperature in the recording layer, the irradiation causes the magnetic domains to contract and eventually disappear. Therefore, the magnetic domain is erased without being erased over the desired length.

In proposing this method, the present inventors manufactured several magneto-optical recording media by changing the composition, film thickness, etc., and conducted an overwrite experiment by the following method. First, the strength P of the magneto-optical recording medium in the stationary state is
A laser pulse having w and a pulse width τw was irradiated under a constant magnetic field Hex applied in a direction perpendicular to the film surface to obtain a range in which magnetic domains were formed (hereinafter, the irradiation condition at this time was A Call the condition). Next, under the condition A, the magneto-optical recording medium is finely moved with respect to the laser beam and continuously oscillates a laser pulse to irradiate the magneto-optical recording medium to obtain stripe magnetic domains. The magnetic domain was irradiated with a laser beam again to obtain a condition for cutting the magnetic domain (hereinafter, the irradiation condition at this time is referred to as A ′ condition).
Next, overwriting was actually carried out based on these conditions. Here, as the magnetic film, a TbFeCo-based amorphous magnetic film having a temperature characteristic shown in FIG.
The results of evaluation using a magneto-optical recording medium having Å) as the recording layer are shown. In this sample, glass was used for the substrate and SiN film was used for the protective film. FIG. 5 shows the above A, in the state where an external magnetic field of 100 Oe is applied in a direction advantageous to magnetic domain writing (a direction opposite to the sublattice moment of the transition metal atom).
This shows the A'condition. Among the conditions A and A'shown in FIG. 5, the condition A is fixed at 10 mW and 1000 nsec, and the intensity and irradiation time to be the condition A'are variously changed, and the condition A is fixed at 15 mW and 200 nsec. Overwrite experiments were conducted under various combinations of irradiation conditions, with various changes in the intensity and irradiation time to be the A conditions. The irradiation positions of the laser pulse on the film surface were set at 0.8 μm intervals. As a result,
As shown in FIG. 5, magnetic domains were formed in the region corresponding to the condition A, and no magnetic domains were formed in the region corresponding to the condition A ′, or the magnetic domains were completely erased if they existed before. This does not depend on the magnetic domain information previously written and is determined only by the binary condition of A and A '. Table 1 shows an example of the combination of the A condition and the A ′ condition and the possibility of overwriting.

[0022]

[Table 1]

From the above, τe ≧ τw, Pw · τw> Pe
・ It was found that particularly good overwrite is possible in the case of τe.

Next, the method (ii) will be described. The device configuration of the magneto-optical recording device used in this system can be as simple as that of the system (i).
As the magneto-optical recording medium to be used, the same medium as in (i) can be used.

In proposing this method, the present inventors conducted the following experiments. That is, a magneto-optical recording medium (TbF) similar to that used in the above-mentioned overwrite experiment.
An eCo film was used as a sample, and the sample was irradiated with a laser beam to perform recording and erasing as follows. During recording, the sample was fixed, the sample was irradiated with laser pulses at various intensities and pulse widths, and the magnetic domain radius formed thereby was measured. For erasing, laser beam irradiation was also performed directly above a cylindrical magnetic domain having a radius of 0.5 μm under various conditions, and the change was examined. The device used has a magnetic shield for the optical pickup in order to reduce the leakage magnetic field of the optical pickup, and the external magnetic field at the recording position on the sample is in a direction advantageous for magnetic domain writing (opposite to the sublattice moment of the transition metal atom). Direction) 10
It was in a state where 0 Oe was applied. An example of the result is shown in FIG.

FIG. 6 shows the results of measuring the magnetic domain radius while changing the pulse width under a pulse intensity of 15 mW. The thick solid line in the figure is the domain radius calculation (BG
HUTH; IBM J.RES.DEV., March 1974), and the thin solid line is the range of the domain radius where the magnetic domain contracts or disappears by laser beam irradiation. The arrow indicates the change in the radius of the magnetic domain when the laser beam is irradiated on the magnetic domain. ◯ indicates the measured value of the write magnetic domain radius, and the broken line arrow indicates the result of actual measurement of the change in the magnetic domain radius when the laser beam irradiation is performed on the cylindrical magnetic domain (the magnetic domain radius is indicated by Δ). From this result, according to the laser beam irradiation conditions, this sample
It was confirmed that the magnetic domain radius can be controlled. In addition, the same experiment as above was carried out for samples in which the magnetic film had magnetic properties of Tcomp <Tr, or samples in which the magnetic film did not have Tcomp. However, in these samples, the phenomenon that the magnetic domains contracted or disappeared was observed. I couldn't do it.

Further, the inventor of the present invention considers the above experimental results.
The sample having the magnetic film having the characteristics shown in FIG.
The sample with various shapes (intensity, pulse width).
Good overwriting by irradiating laser beam pulse
I sought the condition that can be done. As a result, as shown in Fig. 7 (a).
Such a condition (A, B, A ', B'condition), that is, Pw₁<Pe₁  Pw₁・ Τw₁＞ Pe₁・ Τe₁  Pw₂= Pe₂  τw₂= Τe₂  (However, Pw₁, Τw₁Are the first when forming magnetic domains
Intensity and pulse width of laser pulse to irradiate Pw₂,
τw₂Are the lasers that are irradiated after the second one when the magnetic domains are formed.
Intensity and pulse width of laser pulse, Pe₁, Τe₁Is that
Strength of the laser pulse irradiated first when erasing the magnetic domain
Degree and pulse width, Pe₂, Τe₂Are the first
The intensity and pulse of the laser pulse to be emitted after the second
Width. ), Good overwrite can be performed.
I was able to confirm that. Where A, A ', B, B'conditions
The role will be described below.・ A condition is until immediately before
A state without magnetic domains was formed by the condition B'to be described later.
After that, it was carried by B'condition as the subsequent irradiation.
Received the cylindrical magnetic domain, and the edge of the rear end of the magnetic domain
Fix it. Therefore, the ring where the residual heat exists after the B ′ condition irradiation
It is necessary to form a sufficiently sharp edge even in the precincts.
In the experiment, a pulse of 5 mW and 500 nsec was used.・
As for condition B, the condition A irradiation is performed immediately before that, as described above.
After the cylindrical domain is stabilized, the far side of this cylindrical domain
It is used to stretch the magnetic domain while fixing it.
This condition is 15 mW and 200 nsec in FIG.
The laser pulse was good. At this time, the magnetic domain width is 1.
It was around 0 μm. In addition, the B condition and the A condition are
In case of matching, that is, as condition B, condition A above 5 m
Even when W and 500 nsec are used, the magnetic domain is not formed.
It is possible. In this case, reduce the burden on the laser drive unit.
It is advantageous in that the disk rotation speed,
In order to improve the recording frequency etc., the B condition is set independently.
It is advantageous to save it.・ The A'condition is the irradiation performed after the B condition.
To cut the magnetic domain that has been stretched by the B condition.
At the same time, the recorded magnetic domains before overwriting remain in the irradiation area.
If so, it works to erase it. This time
In the example, the 15 mW, 100 nsec laser in FIG.
The pulse was used.・ The B'condition is that after the magnetic domain is erased by the A'condition,
The function of continuing this state without magnetic domains up to the next magnetic domain forming part
To do. As an example, a 15 mW, 200 nsec
Laser pulse was used. Here, B '= B
I will describe the points. When extending a magnetic domain (condition B)
When extending the state without magnetic domains (condition B '),
However, in the case of condition B
Forms a cylindrical magnetic domain in the irradiated area, which
At the time of B'condition irradiation (irradiation to the part with the interval D)
It is pulled up to the irradiation part there (apparent irradiation
It seems that the magnetic domains are moving from the part to the irradiation part).
At that time, if the previously written magnetic domain exists
Was also absorbed by this cylindrical magnetic domain and was irradiated with B'condition.
After that, no magnetic domains will remain. And B'condition check
After firing several times, move to the last B'condition irradiation section.
The moved cylindrical magnetic domain was irradiated by A condition irradiation followed by B condition irradiation.
It will be fixed and become a new recording magnetic domain. Condition B
In the case of irradiation, the magnetic domain fixed by A condition irradiation is cylindrical
Since it can not be drawn as it is,
The domain wall on the far side of the formed cylindrical magnetic domain remains fixed
It will be stretched in a striped pattern. Figure 7 (a)
When irradiated with such a laser pulse, the magnetic domains are shown in Fig. 7 (b).
Is formed like M. In addition, A, B, A ', B'
Table 2 shows an example of the combination of cases.

[0028]

[Table 2]

On the other hand, when the laser beam pulse was irradiated under the conditions shown in FIGS. 1 (c) and 1 (d), good overwriting could not be performed with any combination of pulse intensities.

[0030]

As described above in detail, according to the present invention, since the above-mentioned structure is adopted, high-speed overwriting is possible with a simple device structure and the reliability is excellent. In addition, low power recording is possible, and it is suitable for mark length modulation of signals or mark edge recording.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of laser beam irradiation conditions at the time of recording and erasing in the first method of the present invention.

FIG. 2 is a characteristic explanatory diagram of a magnetic film of a magneto-optical recording medium used in the present invention.

FIG. 3 is a cross-sectional view showing a layer configuration example of a magneto-optical recording medium used in the present invention.

FIG. 4 is an explanatory diagram of a mechanism of forming magnetic domains according to the method of the present invention.

FIG. 5 is an explanatory diagram of a range of recording conditions and erasing conditions of the first method of the present invention.

FIG. 6 is a diagram showing a result of measuring a magnetic domain radius when a pulse width of an irradiation laser beam is changed.

FIG. 7 is an explanatory diagram of laser beam irradiation conditions at the time of recording and erasing in the second method of the present invention.

FIG. 8 is an explanatory diagram of problems in the conventional method.

[Explanation of symbols]

 1 substrate 2 magnetic film 3 protective film

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Ms. Kurosawa 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (6)

[Claims] 1. A magneto-optical recording method for performing overwritable magneto-optical recording by irradiating a magneto-optical recording medium having a single-layered perpendicular magnetization film as a recording layer with a laser beam to control formation and erasure of magnetic domains. A magneto-optical recording method characterized in that a magnetic domain is formed or erased to a desired length by applying a plurality of laser pulses at the time of forming the magnetic domain and at the time of erasing the magnetic domain. 2. The magneto-optical recording method according to claim 1, wherein a plurality of laser pulses of one type are respectively irradiated at the time of forming the magnetic domain and at the time of erasing the magnetic domain. 3. When the intensity of the laser pulse irradiated at the time of forming the magnetic domain is Pw, the pulse width is τw, the intensity of the laser pulse irradiated at the time of erasing the magnetic domain is Pe, and the pulse width is τe,
3. The magneto-optical recording method according to claim 2, wherein the relations .tau.w.gtoreq..tau.e and Pw.multidot..tau.w> Pe.tau.e are satisfied. 4. The magneto-optical recording method according to claim 1, wherein two kinds of laser pulses are combined and a plurality of laser pulses are irradiated at the time of forming the magnetic domain and at the time of forming the magnetic domain. 5. The first method is used both when forming and erasing magnetic domains.
The magneto-optical recording method according to claim 4, wherein different kinds of laser pulses are used for the laser pulse for the second irradiation and the laser pulse for the second and subsequent irradiations. 6. A laser which is irradiated first when forming a magnetic domain.
-Pulse intensity is Pw₁, Pulse width τw₁, The second and later
The intensity of the laser pulse to irradiate Pw₂, Pulse width τ
w₂, Of the laser pulse that is irradiated first when erasing magnetic domains
Strength is Pe₁, Pulse width τe₁, Irradiation after the second
The intensity of the laser pulse is Pe₂, Pulse width τe₂And
Come, Pw₁<Pe₁  Pw₁・ Τw₁＞ Pe₁・ Τe₁  Pw₂= Pe₂  τw₂= Τe₂  6. The relational expression
The magneto-optical recording method described in.