JPH04153934A - Magneto-optical recording and reproducing method and magneto-optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To realize a direct over-write with laser light intensity in a wide allowable range and with excellent reproduction signal quality to practical use by executing in order at least a reverse magnetic field process and an initialization process by the time when a reproducing action or a next recording action is started after the completion of the recording action. CONSTITUTION:For ensuring that the extinguishing of a magnetic domain 13 left un-extinguished due to the application of the reverse magnetic field can be compatible with the direct over-write, it is required to apply in order at least the reverse magnetic field and the initialization magnetic field to a recording area by the time just before executing the next recording or reproduction after the irradiation of recording laser light. Assuming that the sizes of two different inversed magnetic fields of a auxiliary layer 12 are H1 and H2, the reverse magnetic field HINV having a direction reversal to the initialization magnetic field in the range of 0<HINV<H1 and the initialization magnetic field larger than the H1 are applied in order after irradiating th laser light on a medium. Thus, in the magneto-optical recording system capable of over-write by means of a switched connection magnetic thin film, the direct over-write with the laser light intensity in the wide allowable range and with excellent reproduction signal quality can be realize to practical use.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to magneto-optical recording, and in particular to a magneto-optical recording and reproducing method that allows direct overwriting and a magneto-optical recording and reproducing device used therein. This paper relates to improvements in optical modulation override methods using coupled multilayer films.

[Conventional technology 1] In recent years, research has been actively conducted on magneto-optical recording, which uses a perpendicularly magnetized film as a recording layer, as one of the rewritable optical recording methods, and first-generation recording/reproducing devices and recording media have become commercially available. It has come to be However, in order to rewrite information in this first generation recording/playback device, it is necessary to go through two steps: erasing the information that has already been written, and writing new information. Direct override is not possible, and the actual transfer speed of information is considered to be inferior to fixed magnetic disk devices.

Therefore, many efforts are being made to establish technology to realize direct override, and one of them is JP-A-62-17
A so-called optical modulation override method has been proposed in which an exchange-coupled multilayer film as disclosed in No. 5948 and the like is used as a recording medium.

In this direct override method, a recording medium in which a first magnetic layer called a recording layer and a second magnetic layer called an auxiliary layer are sequentially laminated on a substrate is used. By applying an initialization magnetic field of an appropriate magnitude, the direction of magnetization of the auxiliary layer is aligned in one direction while the direction of magnetization of the recording layer remains in a state corresponding to the already recorded binary information. At the same time, a writing magnetic field of an appropriate magnitude is applied, and at the same time a laser beam is applied that gives a relatively low medium temperature (hereinafter referred to as recording), or a laser beam that gives a relatively high medium temperature is applied ( Recording is performed using H recording (hereinafter referred to as H recording). In L recording, the direction of magnetization of the auxiliary layer does not change, and the exchange coupling energy of the magnetization of the recording layer becomes lower than that of the auxiliary layer. In H recording, since a high medium temperature is achieved, the direction of magnetization of the auxiliary layer is reversed by the write magnetic field, and then the magnetization of the recording layer becomes in a state where the exchange coupling energy is lower than that of the auxiliary layer.

By applying the initialization magnetic field again, the auxiliary layer is aligned in one direction after recording, and the direction of magnetization of the recording layer shifts to a state in which it matches the direction after writing.

[Problems to be Solved by the Invention] In direct override, in order to reliably record new information, it is necessary to eliminate any unerased information from the previous one. As a result of a deep study of the conventional direct override method, it was found that unerased data in L recording poses a problem. In FIG. 3, the apparent magnetization state of each layer in the area where L recording is performed when such a magneto-optical recording medium is used is illustrated by arrows, and will be explained. The magnetic layer in this explanation is that the recording layer 31 is a rare earth transition metal alloy ferrimagnetic film rich in transition metal magnetic moments at room temperature, and the auxiliary layer 32 is a rare earth metal magnetic moment film with a compensation temperature between room temperature and the Curie temperature. It is a combination of rich rare earth transition metal alloy ferrimagnetic film.

If the recording is completed completely in the L recording, Fig. 3 (
As shown in Figure 3 (a), the magnetization of the recording layer is oriented in a direction where there is no interfacial domain wall with respect to the auxiliary layer, but in reality it is reversed in the recording layer as shown in Figure 3 (b) or Figure 3 (c). Magnetic domain regions 33 are often observed. It turned out that this was acting as an eraser.

Due to fluctuations in the magnetic properties of the recording medium, focus servo residuals, etc., transfer due to the magnetization of the auxiliary layer may not take place in a certain part, forming a minute magnetic domain, or an uninverted region may remain in the auxiliary layer during the initialization process. is the cause of this unerased image. In conventional techniques, in order to eliminate this unerased area, the intensity of the laser beam for L recording is increased or the initialization magnetic field is increased. Although these methods provide a certain degree of improvement, the former has the disadvantage that the permissible range of laser light intensity suitable for L recording becomes narrow. In addition, in the latter method, it is difficult to generate a large initializing magnetic field due to the design of the magneto-optical recording device.
It's not a practical method.

Furthermore, there is a demand for the use of a magnetic film with a high Curie temperature in the recording layer in order to improve the reproduction signal quality, but this poses a problem in that the laser power required for L recording increases.

The present invention has been made to solve these problems, and its purpose is to provide magneto-optical recording and reproducing that achieves direct override with a wide permissible range of laser light intensity and good reproduction signal quality. An object of the present invention is to provide a method and a magneto-optical recording/reproducing device.

[Means to solve the problem] The above objects can be achieved by the following invention.

That is, the magneto-optical recording and reproducing method of the present invention comprises a first magnetic layer having a relatively large coercive force and a low Curie point at room temperature, which are exchange-coupled with each other at room temperature, and a first magnetic layer having a relatively small coercive force and a high Curie point at room temperature. A laminated film of a second magnetic layer having a dot is used as a magneto-optical recording layer, and the absolute values of the two reversal magnetic fields of the minor loop in the magnetization curve of the second magnetic layer are H.

H, (H,>H2), and by applying an initialization magnetic field larger than Hl in the direction perpendicular to the film surface, a disk-shaped magneto-optical structure is created in which only the direction of magnetization of the second magnetic layer is aligned in one direction. Using a recording medium, (a) applying a recording magnetic field perpendicular to the film surface of the magneto-optical recording medium and simultaneously irradiating a laser beam to achieve a first heating state, thereby causing magnetization reversal in a second magnetic layer; Either a first recording state in which only the heated region of the first magnetic layer is magnetized in a stable direction with respect to the second magnetic layer without causing the magnetization to occur, or a second heating state in which a laser beam is irradiated at the same time as the recording magnetic field is applied. By realizing this, first the magnetization of the heated region of the second magnetic layer is reversed, and then the first magnetic layer is magnetized in a stable direction relative to the second magnetic layer. Recording operation performed accordingly (b) Irradiating the area where the recording operation was performed with a laser beam,
In a magneto-optical recording and reproducing method comprising a reproducing operation of detecting the direction of magnetization formed in a first magnetic layer and reproducing information, (c) applying the initializing magnetic field to the area where the recording operation has been performed; (d) When defining a reverse magnetic field process in which a static magnetic field smaller than Hl is applied in the opposite direction to the initialization magnetic field to the area where the recording operation has been performed, after the recording operation is completed, the reproducing operation, or It is characterized in that at least a reverse magnetic field process and an initialization process are performed in order immediately before starting the next recording operation. Here, the effect may be further enhanced by adding an initialization process before the reverse magnetic field process.

Furthermore, the magneto-optical recording and reproducing method of the present invention includes a means for rotating a magneto-optical recording medium, an optical head, a means for generating the initializing magnetic field at a position different from the optical head, and a magnetic layer on a magnetic layer of the magneto-optical recording medium. A conventional optical modulation override system comprising: laser modulation means for realizing the first and second heating states according to recording information; and means for applying the recording magnetic field to the magneto-optical recording medium when recording information. This can be concretely realized by adding the above-mentioned static magnetic field generating means to a magneto-optical recording/reproducing device used for.

[Function] The magneto-optical recording and reproducing method of the present invention comprises a recording layer having a relatively large coercive force and a low Curie point at room temperature, and an auxiliary layer having a relatively small coercive force and a high Curie point at room temperature, The magnetic properties at room temperature are as follows: σ is the interfacial domain wall energy density between both layers, and M is the saturation magnetization of the auxiliary layer.
,, When the thickness of the auxiliary layer is h2, the coercive force of the recording layer is Hcl, and the coercive force of the auxiliary layer is Hc2, JP-A-62-175
A magneto-optical recording medium that satisfies the requirements is used, similar to those disclosed in No. 948 and Japanese Patent Application Laid-Open No. 63-153752.

As shown in the problem to be solved by the invention, the unerased area in the L recording is as shown in FIG. 3(b) or FIG. 3(c).
It is in a state like this.

First, as shown in FIG. 1(a), a third
A case will be considered in which a static magnetic field H10, which is in the opposite direction to the initialization magnetic field (hereinafter, this magnetic field will be referred to as a reverse magnetic field), is applied to the eraser residue 13 of the type shown in FIG. 2B. Now, if the domain wall energy density of the cylindrical domain wall of the recording layer is σ8, the saturation magnetization of the recording layer is M51, the film thickness of the recording layer is R, and the radius of the unerasable magnetic domain is R, then 0 <Hl-< H1+□ ・ ・ (
1) 2M, h.

When , a simple consideration based on the bubble domain theory that ignores the demagnetizing field term for a cylindrical domain assuming a perfect circle shows that when , the residual domain disappears and a normal state as shown in Figure 1 (b) is obtained. It can be seen that the image settles into an erased state. Also, 0<H,,+-<H,,<H,+--(3)2M,h,
2M,,h.

Also when satisfying the following, the auxiliary layer 22 is uniformly magnetized.
It can be seen that after passing through the state shown in FIG. 1(c) and reaching the magnetization state shown in FIG. 1(d), the application of the initialization magnetic field HZai settles into the normal erased state shown in FIG. 1(b).

On the other hand, in the case of the type of unerased material shown in Figure 3(c), H14
, satisfies equation (1), the unerasable magnetic domain does not immediately disappear simply by passing through the reverse magnetic field, but once it passes through the initializing magnetic field, the auxiliary layer becomes uniformly magnetized, as shown in Figure 3(b). Therefore, by applying a second reverse magnetic field as the magneto-optical recording medium rotates, it follows the same path as in the above case and the remaining part disappears according to equation (2). Also,
When Hl, , v satisfy equation (3), the unerased portion disappears according to equation (4) following the same path as in FIG. 3(b) considered earlier.

The states of the inverted magnetic domain formed by H recording immediately after and immediately before passing through the initialization magnetic field are shown in FIG. 3(b) and FIG. 3(b), respectively.
The remaining magnetic domain shown in FIG. 3(c) has a similar shape except for the magnetic domain diameter. Therefore, this recording magnetic domain also behaves according to the above-mentioned magnetic domain theory, so the diameter of the recording magnetic domain is large (
If the equations 2) and (4) are not satisfied, the remaining magnetic domains will not disappear. Therefore, in equations (2) and (4), by applying a reverse magnetic field H1 of an appropriate magnitude so that the unerasable magnetic domain disappears and the recorded magnetic domain does not disappear, a large magnetic domain corresponding to the recorded information is created. It is possible to erase only the remaining magnetic domains without destroying them.

By the way, the annihilation of unerasable magnetic domains by a reverse magnetic field occurs when the magnitude of the reverse magnetic field H1,... is within the range of equation (1) and (3
), but as can be seen from equations (2) and (4), the annihilation of the remaining parts is achieved with a much smaller reverse magnetic field when equation (1) is satisfied. can do. Therefore, it can be seen that it is practically preferable to satisfy formula (1).

Now, an important point in the optical modulation override method using this exchange-coupled multilayer film is that the auxiliary layer must be uniformly magnetized prior to irradiation with the recording laser beam. Therefore, immediately before starting the next recording operation, it is necessary to achieve at least the state immediately after application of the initializing magnetic field. In other words, in order to achieve both annihilation of unerasable magnetic domains and direct override by applying a reverse magnetic field that satisfies the above-mentioned formula (1), it is necessary to at least add at least It is necessary to apply a reverse magnetic field and an initializing magnetic field in this order.

As mentioned above, in a magneto-optical recording medium that uses an exchange-coupled multilayer film and is capable of optical modulation override, the magnitudes of two switching magnetic fields of different auxiliary layers, Hl and H2, are defined as shown in Figure 2. , after irradiating the medium with recording laser light,
By sequentially applying a reverse magnetic field H17, which is in the opposite direction to the initializing magnetic field, and an initializing magnetic field larger than Hl in the range O<Hl, , <Hl, it is possible to realize a good direct override that suppresses unerasing. can. Furthermore, depending on the type of unerased material, it may be more effective to apply an initializing magnetic field before applying the reverse magnetic field. Note that the lower limit of the reverse magnetic field strength to obtain a practical effect varies depending on the magneto-optical recording medium used, but
- In terms of number, it is about 500 to 10,000e.

This type of magneto-optical recording and reproducing method uses an optical head that can modulate the intensity of laser light according to recorded information and a mechanism that generates a recording magnetic field at the recording light irradiation position when using a disc-shaped magneto-optical recording medium. , to be realized by a magneto-optical recording/reproducing device in which a mechanism for generating an initializing magnetic field at a different position, a mechanism for generating a reverse magnetic field in the opposite direction to the initializing magnetic field, and a mechanism for rotating the substrate are appropriately arranged. I can do it. That is, the same
When a recording magnetic field generation mechanism, a reverse magnetic field generation mechanism, and an initialization magnetic field generation mechanism are arranged on a radius in order in the rotational direction of the magneto-optical recording medium, at least one rotation after irradiation with the recording laser beam, and in some cases two rotations. During this time, all the operations required for recording are completed, and the recording magnetic field generating mechanism, initializing magnetic field generating mechanism, reverse magnetic field generating mechanism, and initializing magnetic field generating mechanism are arranged in order in the rotation direction of the magneto-optical recording medium on the same radius. In this case, all operations required for recording are completed during one rotation after irradiation with the recording laser beam.

In the magneto-optical recording medium used in the explanation, the recording layer is a rare earth transition metal alloy ferrimagnetic film rich in transition metal magnetic moment at room temperature, and the auxiliary layer is a rare earth metal magnetic moment film with a compensation temperature between room temperature and the Curie temperature. Although the exchange-coupled film consists of two magnetic layers of a rich rare-earth transition metal alloy fabricated magnetic film, other types of exchange-coupled films and intermediate layers that are effective in suppressing the domain wall energy between the two layers have been developed. The same explanation can be given using the introduced magneto-optical recording medium.

[Example] The present invention will be described in detail below based on Examples.

Embodiment 1: FIG. 4 is a block diagram of a magneto-optical recording/reproducing apparatus according to the present invention. A reverse magnetic field generator 46 is installed on the circumference of a disk-shaped magneto-optical recording medium 41 that is rotated in the direction of the arrow by a motor 42.
, an initialization magnetic field generator 44, and an optical head 43 with laser modulation means are arranged in this order. Further, the recording magnetic field generating device 45 is arranged to face the optical head with the magneto-optical recording medium in between. With this configuration, the signal recording area on the medium repeatedly passes through the reverse magnetic field generating device, the initializing magnetic field generating device, and the optical head (recording magnetic field generating device) in this order as the disk rotates. Note that the laser light wavelength for recording and reproduction is 780 nm, and the laser light is incident from the substrate side of the magneto-optical recording medium.

Next, the magneto-optical recording medium used in this example will be explained. That is, as shown in FIG. 5, a protective layer 5 is formed on a resin substrate 51.
2 is 80 nm, the recording layer 53 is 50 nm, and the auxiliary layer 54 is 1
A magneto-optical recording medium was constructed by laminating a protective layer 55 with a thickness of 100 nm and a protective layer 55 with a thickness of 80 nm in this order. Here, the recording layer is made of NdDyTbFe in which transition metal sublattice magnetization is dominant (7M rich) at room temperature.
In Co, sublattice magnetization of rare earth metal is dominant in the auxiliary layer (R
Two levels of samples (Sample 1, Sample 2) with different magnetic properties were used.
) was prepared. Table 1 shows the apparent coercive force and Hl of the recording layer and auxiliary layer of these samples. The apparent coercive force here refers to the amount shifted from the coercive force of a single layer film as a result of exchange coupling between the recording layer and the auxiliary layer. However, for the auxiliary layer, in the reversal magnetic field of the minor loop of the magnetization curve, the one with the larger absolute value (i.e. Hl in Figure 2)
is the value of

Table 1 As described above, these samples used in this example had a recording layer having a composition rich in 7M and an auxiliary layer having a composition rich in RE.

In the magneto-optical recording/reproducing apparatus shown in FIG. 4, the initializing magnetic field is applied in the same direction as the recording magnetic field, and the reverse magnetic field is applied in the opposite direction to the recording magnetic field.

To evaluate the permissible range of the L recording laser power, that is, the power margin, when a 2 MHz signal is overridden in the area of a magneto-optical recording medium where a 7 MHz signal has been recorded, the unerased intensity of the signal before override is measured using a spectrum analyzer. This was done by doing. The relative moving speed of the recording medium during recording and reproduction was 15 m/sec, and the laser power for H recording was 15 mW.

Figures 6(a) and (b) are plots of the signal intensity levels of unerased signals after override for Sample 1 and Sample 2, respectively, against the laser power of L recording, and the power at which the unerased signals disappear is calculated. PL. Here, the initialization magnetic field is 4.0
There are two levels of kOe and reverse magnetic field, 2.0 kOe and 4.0 kOe, and for comparison, a conventional magneto-optical recording and reproducing method in which no reverse magnetic field is applied is also shown. Figure 6(a)
It can be seen from (b) that PL can be lowered by applying a reverse magnetic field.

In other words, it can be seen that the power margin for L recording is expanded. In particular, when the reverse magnetic field strength is 2.0 kOe for both samples 1 and 2, the PL decreases by about 1.5 mW, which is clearly effective in expanding the power margin of L recording.

Next, for sample 1 and sample 2, the reverse magnetic field was set to 0. 7 from OOe
．． Figures 7(a) and 7(b) show the changes in P when changing it every 0.5 kOe up to 0 kOe. Here, the initialization magnetic field is 4.0 kOe. As is clear from FIG. 7 and Table 1, P is the value P when the reverse magnetic field is 0.00e. PL continues to decrease from to just below the apparent coercive force (Hl) of the auxiliary layer, and when Hl is exceeded, PL changes discontinuously again to around PL0, and then gradually decreases from there. Therefore, it can be seen that the reverse magnetic field greatly contributes to a decrease in PL, that is, an increase in the power margin of L recording, especially in the region below H1.

Embodiment 2: FIG. 8 is a block diagram of a magneto-optical recording and reproducing apparatus according to the present invention. On the circumference of a disk-shaped magneto-optical recording medium 81 rotated in the direction of the arrow by a motor 82, there are an initializing magnetic field generator 84, a reverse magnetic field generator 86, another initializing magnetic field generator 84', and a laser modulation means. The optical heads 83 are arranged one after another. Further, the recording magnetic field generating device 85 is arranged to face the optical head across the magneto-optical recording medium. By adopting such a configuration, the signal recording area on the medium is divided into the initializing magnetic field generating device 84, reverse magnetic field generating device, initializing magnetic field generating device 84', and optical head (recording magnetic field generating device) as the disk rotates. (Hereinafter, the magnetic field generated by the initialization magnetic field generator 84° will be referred to as the first initialization magnetic field, and the magnetic field generated by the initialization magnetic field generator 84 will be referred to as the second initialization magnetic field.) Note that the laser light wavelength for recording and reproduction is 780 nm, and the laser light is incident from the substrate side of the magneto-optical recording medium.

Next, the magneto-optical recording medium used in this example will be explained. In FIG. 5, the recording layer 53 is made of NdDyTbFeC.
DyFeC with o as 5 Onms auxiliary layer 54.

Two levels of samples (sample 3.4) with different magnetic properties were prepared using Al5iN with a thickness of 80 nm and a protective layer of 52.55% with a thickness of 100 nm. Table 2 shows the apparent coercive forces H, . . . Hl defined in Example 1 of the recording layer and auxiliary layer of these samples.

In all the samples in Table 2, the recording layer is 7M rich and the auxiliary layer is RE rich. Therefore, in the magneto-optical recording/reproducing apparatus shown in FIG. 8, the two initializing magnetic fields are applied in the same direction as the recording magnetic field, and the reverse magnetic field is applied in the opposite direction to the recording magnetic field.

Figures 9(a) and 9(b) show the remaining data when a 2 MHz signal is overridden on a 7 MHz signal at a recording/reproducing linear velocity of 17 m/sec and an H recording laser power of 15 mW for Samples 3 and 4, respectively. The signal intensity level is plotted against the laser power for L recording. Here, both the first initialization magnetic field and the second initialization magnetic field are 4.0k.
Oe, and the reverse magnetic field was 2.0 kOe. For comparison, a conventional magneto-optical recording and reproducing method in which no reverse magnetic field was applied is also shown. According to FIGS. 9(a) and 9(b), it can be seen that by applying a reverse magnetic field, P can be reduced by 1.5 mW or more.

By the way, in this evaluation, one track jump is performed immediately after the recording operation is completed, and during the transition from the recording operation to the reproduction operation, the second initialization magnetic field, reverse magnetic field, and first initialization magnetic field are sequentially changed to 1.
Reproduction was performed after applying the voltage to the recording area only once. Therefore, as described in the operation section of the present application, as shown in FIG.
) type of unerased areas as well, it can be expected that the above-mentioned results include the effect of eliminating unerased areas. In order to confirm this, sample 3 was prepared in the magneto-optical recording/reproducing apparatus shown in Fig. 8 for both the case (a) without the second initializing magnetic field and the case (b) without the second initializing magnetic field and reverse magnetic field. When the dependence of the unerased signal on the L recording laser power was measured using this method, the results shown in FIG. 10 were obtained.

Note that FIG. 10 also shows the results for the case (c) when there is a second initialization magnetic field and a reverse magnetic field. According to this,
It can be seen that in comparison with (b), in (a), the unerased area is minimized, the recording power is lowered, and the power margin for L recording is expanded, similar to that shown in Example 1 of the specification of the present application.

However, when comparing (a) with (c), it is found that although there is no difference in the L recording power at which the unerased area is minimized, there is a difference of approximately 5 dB in the carrier level of the unerased area. That is, in the magneto-optical recording medium used in this example, there is a residual magnetic domain of the type shown in FIG. However, by introducing a reverse magnetic field and a second initialization magnetic field, it is possible to eliminate this type of unerased data.

Example 3: This example demonstrates that the present invention can increase the Curie temperature of the recording layer and increase the Kerr rotation angle of the medium without deteriorating the power margin of L recording and the L recording sensitivity. The magneto-optical recording and reproducing apparatus used here is the same as that shown in FIG. 4 in Example 1 of the present specification. Further, in the magneto-optical recording medium used in this example, the recording layer 53 is made of NdDyTbFe in FIG.
50 nm of Co, 11 nm of DyFeCo as the auxiliary layer 54
00n, Al5iN as protective layer 52.55, respectively 80
Two levels of samples with different magnetic properties (
Samples 5 and 6) were prepared. In each sample, the recording layer is TM-rich, and the auxiliary layer is RE-rich. Further, the auxiliary layer is the same for samples 5 and 6. The Curie temperature Tc of the recording layer of these samples and the apparent coercivity H, n, H of the recording layer and auxiliary layer defined in Example 1.

are shown in Table 3.

Table 3 Samples 5 and 6 both have a recording layer that is TM rich and an auxiliary layer that is R.
Since it has an E-rich composition, the initializing magnetic field is applied in the same direction as the recording magnetic field, and the reverse magnetic field is applied in the opposite direction to the recording magnetic field, as shown in FIG. The relative moving speed of the recording medium surface during recording and reproduction is 17 m/sec, and a 2 MHz signal is overridden on a 7 MHz signal. The laser power for H recording was fixed at 15mW, and the initialization magnetic field was 4.0k.
Oe.

The reverse magnetic field strength was 2.0 kOe, and for comparison, a reverse magnetic field of 0.0 kOe, which corresponds to the conventional magneto-optical recording and reproducing method, was also investigated.

Table 4 shows that the unerased signal measured by the above method disappears, the recording laser power PL and the carrier-to-noise ratio (c/ N ratio).

Table 4 First, from Table 4, it can be seen that the medium (Sample 6) whose recording layer has a higher Curie temperature has a higher C/N ratio.

On the other hand, the medium with a higher Curie temperature of the recording layer has a higher PL.
It turns out that it is necessary. However, even in sample 6, which has a high Curie temperature, when the inverse magnetic field of the present invention is introduced,
It can be seen that it is possible to lower P to a level equivalent to that when the sample 5 is recorded by the conventional magneto-optical recording and reproducing method without a reverse magnetic field, and that high sensitivity can be achieved with respect to the laser power of L recording. On the other hand, by using the reverse magnetic field according to the present invention, the Kerr rotation angle can be increased by increasing the Curie temperature of the recording layer without deteriorating the power margin for L recording and the recording sensitivity.
This shows that it is possible to increase the C/N ratio of the medium.

Note that in these examples, each magnetic layer is made of TbFeCo.
, TbFeCoCr, DyTbFeCo, NdD
yFeC.

, SmDyFeCo, PrDyFeCo, etc., results similar to those described above were obtained.

[Effects of the Invention] According to the present invention, in an overridable magneto-optical recording method using an exchange-coupled magnetic thin film, it is possible to realize gray left overwriting with a wide permissible range of laser light intensity and good reproduction signal quality. A magneto-optical recording and reproducing method and a magneto-optical recording and reproducing apparatus can be provided. Furthermore, it is also possible to effectively eliminate unerased areas caused by incomplete initialization, which could not be eliminated using conventional methods.

[Brief explanation of drawings]

FIGS. 1(a), (b), (c), and (d) are diagrams used to explain the present invention, showing the state of magnetization of a recording medium. 11: Recording layer 12: Auxiliary layer 13: Remaining magnetic domain FIG. 2 is a diagram showing a minor loop of the magnetization curve of the auxiliary layer. Figure 3 (a) shows the apparent magnetization state of the recording layer and auxiliary layer when L recording is completed, and Figures 3 (b) and (c) show the apparent magnetization state of the recording layer and auxiliary layer when there is some unerased area in the L recording area. Diagram indicated by arrow. 31: Recording layer 32: Auxiliary layer 33: Remaining magnetic domain FIG. 4 is a block diagram of a magneto-optical recording and reproducing apparatus in Example 1 according to the present invention. 41: Magneto-optical recording medium 42: Motor 43: Optical head 44: Initialization magnetic field generator 45: Recording magnetic field generator 46: Reverse magnetic field generator FIG. 5 is a side sectional view of the recording medium used in this example. 51: Resin substrate 52: Protective layer 53: Recording layer 54: Auxiliary layer 55: Protective layer
FIG. 4 is a diagram showing the relationship between the L recording laser power and the unerased level for sample 2. FIGS. 7(a) and 7(b) show sample 1 in Example 1, respectively.
A diagram showing the relationship between the reverse magnetic field and PL of sample 2. FIG. 8 is a diagram showing the positional relationship of each magnetic field generating device in the recording/reproducing apparatus in Example 2. 81: Magneto-optical recording medium 82: Motor 83: Optical head 84.84゛: Initialization magnetic field generator 85: Recording magnetic field generator 86: Reverse magnetic field generator , each sample 3
3 is a diagram showing the relationship between the recording laser power and the unerased level using the magneto-optical recording and reproducing method and the magneto-optical recording and reproducing apparatus of the present invention for Sample 4 and Sample 4. FIG. FIG. 10 is a diagram showing the relationship between recording laser power and unerased level of sample 3 in Example 2. Applicant Seiko Epson Corporation Representative Patent Attorney Kizobe Suzuki (1 other person) (a) Figure 1 (c) Figure 3 Figure 5 4.0 5.0 6. OL recording laser power (mW) (a) 4.0 5.0 6. OL recording laser power (mW) (b) Fig. 6 Reverse magnetic field (koe) (a) Reverse magnetic field (koe) (b) Fig. 7 4.0 5.0 6. OL recording laser power (mW) (a) 7.0 4.0 5.0 6. OL recording laser power (mW) (b) Figure 9 7.0

Claims (3)

[Claims] (1) A first magnetic layer having a relatively large coercive force and a low Curie point at room temperature and a second magnetic layer having a relatively small coercive force and a high Curie point at room temperature, which are exchange coupled to each other at room temperature. The laminated film of is used as a magneto-optical recording layer, and the absolute values of the two reversal magnetic fields of the minor loop in the magnetization curve of the second magnetic layer are H_1 and H_2 (H_1>H_
2), using a disk-shaped magneto-optical recording medium in which only the direction of magnetization of the second magnetic layer is aligned in one direction by applying an initializing magnetic field larger than H_1 in the direction perpendicular to the film surface. a) By applying a recording magnetic field perpendicular to the film surface of the magneto-optical recording medium and simultaneously irradiating laser light to achieve the first heating state, the first heating state is achieved without causing magnetization reversal in the second magnetic layer. Either the first recording is performed by magnetizing only the heated region of the magnetic layer in a stable direction relative to the second magnetic layer, or the second heating state is achieved by applying a recording magnetic field and irradiating laser light at the same time. First, the magnetization of the heated region of the second magnetic layer is reversed, and then the first magnetic layer is magnetized in a stable direction with respect to the second magnetic layer. b) irradiating the area where the recording operation has been performed with a laser beam;
In a magneto-optical recording and reproducing method comprising a reproducing operation of detecting the direction of magnetization formed in a first magnetic layer and reproducing information, (c) applying the initializing magnetic field to the area where the recording operation has been performed; (d) When defining a reverse magnetic field process in which a static magnetic field smaller than H_1 is applied to the area where the recording operation has been performed in the opposite direction to the initialization magnetic field, after the recording operation is completed, the reproducing operation, or A magneto-optical recording and reproducing method characterized in that at least a reverse magnetic field process and an initialization process are sequentially performed immediately before starting the next recording operation. (2) The magneto-optical recording and reproducing method according to claim 1, characterized in that an initialization process is performed before the reverse magnetic field process. (3) means for rotating the magneto-optical recording medium; an optical head; means for generating the initializing magnetic field at a position different from the optical head; In a magneto-optical recording and reproducing apparatus, the magneto-optical recording and reproducing apparatus includes a laser modulation means for realizing the first and second heating states, and a means for applying the recording magnetic field to the magneto-optical recording medium during recording of information, the magneto-optical recording and reproducing apparatus comprising: A magneto-optical recording and reproducing device comprising: