JP3077848B2 - Magneto-optical recording medium, magneto-optical recording method, and magneto-optical reproducing method - Google Patents

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 medium for magneto-optically recording information and a magneto-optical recording method using the same.
The present invention relates to a magneto-optical reproducing method .

[0002]

2. Description of the Related Art In recent years, a magneto-optical recording / reproducing apparatus using a magneto-optical disk as a recording medium has been greatly expected because of its portability, large storage capacity, and erasable / rewritable data. I have. In order to further improve the performance, research on overwriting to increase the data transfer speed, research on direct verification, and research on increasing the storage capacity have been actively conducted. FIG. 13 is a configuration diagram showing an optical system of the general magneto-optical recording / reproducing apparatus. In FIG. 13, reference numeral 41 denotes a semiconductor laser provided as a light source, and divergent light from the laser is collimated by a collimator lens 42, and is incident on an objective lens 45 via a beam shaping prism 43 and a polarizing beam splitter 44. . Then, the light is condensed to form a light spot on the magnetic layer of the magneto-optical recording medium 46. On the other hand, the magnetic head 47 applies an external magnetic field to the light spot irradiation site. The reflected light from the magneto-optical recording medium 46 is
Again through the objective lens 45, the polarization beam splitter 44
, Where a part of the reflected light is separated and brought to the control optical system. In the control optical system, the separated light beam is further separated by a separately prepared polarizing beam splitter 48, and one of the separated light beams is supplied to a reproducing optical system 49 to obtain an information signal. The other is supplied to a photodetector 57 via a condenser lens 55 and a half prism 56, and further to a photodetector 59 via a half prism 56 and a knife edge 58. Is generated. The reproduction optical system 49 sets the polarization direction of the light beam to four.
A half-wave plate 50 for rotating by 5 degrees, a condenser lens 51 for condensing the light beam, a polarization beam splitter 52 for separating the light beam, and a light for detecting each of the light beams separated by the polarization beam splitter 52 It comprises detectors 53 and 54. The reproduction data is generated using a signal obtained by differentially detecting the signals from the photodetectors 53 and 54.

FIG. 14 is a diagram for explaining how a magneto-optical signal as the reproduction signal is obtained. The magneto-optical recording medium 46 records information based on the difference in the direction of magnetization. When linearly polarized light is applied to the medium, when the direction of polarization of the linearly polarized light is clockwise or counterclockwise due to the difference in the direction of magnetization. Rotate. For example, the polarization direction of the linearly polarized light incident on the magneto-optical recording medium is set to the coordinate axis P direction shown in FIG. 14, the reflected light for the downward magnetization is R ₊ rotated by + θ _k, and the reflected light for the upward magnetization is R ₋ rotated by −θ _k. And Therefore, when placing the analyzer in a direction as shown in Figure 14, A light whereas R ₊ coming through the analyzer, R _- to B, and the difference in light intensity which upon detection by the light detector Information can be obtained. In the apparatus shown in FIG. 13, the polarizing beam splitter 52 serves as an analyzer. One of the separated light beams is +45 degrees from the P axis, and the other light beam is
It becomes an analyzer in the direction of -45 degrees from the P axis. That is, since the signal components obtained by the photodetectors 31 and 32 have opposite phases,
By differentially detecting individual signals, a reproduced signal with reduced noise can be obtained.

By the way, as an overwriting method,
An optical modulation method and a magnetic field modulation method are known. In the light modulation method, as shown in FIG. 15, an objective lens 62 of an optical head and a bias magnet 61 are arranged opposite to each other with a magneto-optical recording medium 63 interposed therebetween. This is a method of irradiating a light spot whose intensity is modulated according to a recording signal. The initialization magnet 60 is a magnet for initializing the recording auxiliary layer 65 of the magneto-optical recording medium 63. As the magneto-optical medium 63 used for the light modulation system, the protection and interference layer 6 on the transparent substrate 68 is used.
7, a recording layer 66, a recording auxiliary layer 65, and a protective layer 64 are formed, and those having characteristics as shown in FIG. 16 are used. FIG.
Reference numeral 6 denotes a characteristic of the coercive force with respect to the temperature of the recording auxiliary layer 65 and the recording layer 66, 69 denotes a characteristic curve of the recording auxiliary layer 65, and 70 denotes a characteristic curve of the recording layer 66. As is clear from FIG. 16, the recording auxiliary layer 65 has a coercive force H _C69 at room temperature.
Small, has a high Curie temperature T _C69, also increased coercivity H _C70 at room temperature than the recording auxiliary layer 65 as the recording layer 66 has a lower Curie temperature T _C70. In FIG. 16, T _comp is the compensation point temperature of the recording auxiliary layer 65, H _ini is the magnitude of the initial magnetic field, H _w is the magnitude of the bias magnetic field, T _R is the temperature during reproduction, and T _WL and T _WH are It shows the low level and high level temperatures during light modulation during overwriting.

FIG. 17 shows a timing chart of a recording operation by the light modulation method. In this recording, it is assumed that the magneto-optical recording medium 63 in FIG. 15 is moving in the direction of arrow B. In the light modulation method, first, the recording auxiliary layer 65 is magnetized in one direction at room temperature by the magnetic field H _ini of the initialization magnet 60. Then, when the information recording point of the magneto-optical recording medium 63 passes through the bias magnet 61, by applying a bias magnetic field H _W as shown in FIG. 17, for irradiating a light spot from the optical head at the same time. The light intensity of the light spot is modulated in accordance with a recording signal to the low level power P _L and the high level P _H, the temperature of the information recording points is T _WL, T _WH. In this case, when the optical power is at the high level P _H , the temperature T _WH of the recording auxiliary layer 65 exceeds the Curie temperature T _C69 , so that the recording auxiliary layer 65
Is reversed to the direction of the bias magnetic field. Also,
When the optical power is at the low level P _L , the original magnetization direction is maintained. In this manner, magnetic domains are formed in the recording auxiliary layer 65 as shown in FIG. 17, and the magnetic domains are transferred to the recording layer 66 when the magnetic layer is cooled. The shape of the magnetic domain is a circle or an ellipse, and the length W _O is determined by the magnitude of the light intensity, the time for irradiating high-level light, the speed of the medium, and the like. When the irradiation time is very short, it is almost determined by the magnitude of the light intensity. FIG. 18 is a view showing this state. When a light spot 72 having a temperature distribution of 71 is irradiated in a pulse shape and the temperature shown by a dotted line is the Curie temperature of the recording layer, the pit 73 actually recorded is , Smaller than the size of the light spot 72.

On the other hand, in the magnetic field modulation system, as shown in FIG. 19, a magnetic head 74 and an objective lens 75 of the optical head are arranged opposite to each other with a magneto-optical recording medium 76 interposed therebetween, and the magnetic head 74 is irradiated with a light beam of a predetermined intensity. This is a method in which a magnetic field modulated according to a recording signal is applied from the head 74. The magneto-optical recording medium 76 used for the magnetic field modulation system includes a protective and interference layer 80, a reproducing layer 79, a recording layer 78, and a protective layer 7 on a transparent substrate 81.
Reference numeral 7 denotes a laminated structure. FIG. 20 shows the coercive force characteristics of the recording layer 78 and the reproducing layer 79 with respect to the temperature.
2 is a characteristic curve of the recording layer 78, and 83 is a characteristic curve of the reproducing layer 79. As is clear from FIG. 20, the recording layer 78 has a large coercive force H _C82 at room temperature and a low Curie temperature T _C82.
The reproducing layer 79 has a smaller coercive force H _C83 at room temperature than the recording layer 78 and has a higher Curie temperature T _C83 . In FIG. 20, T _comp 'indicates the compensation point temperature of the recording layer 78, H _w ' indicates the magnitude of the modulation magnetic field, T _R 'indicates the temperature at the time of reproduction, and T _W ' indicates the temperature at the time of overwriting.

Next, the recording operation by the magnetic field modulation method will be described with reference to FIG.
This will be described with reference to FIG. It is assumed that the magneto-optical recording medium 76 in FIG. 19 is moving in the direction of arrow C. In the magnetic field modulation method, the light intensity of the light beam is irradiated at a constant power P _W , and the temperatures on the magnetic layer of the magneto-optical recording medium 76 are T _W 'and T
_Heated during _C82 . With the temperature raised, a magnetic field modulated to ± H _W ′ is applied from the magnetic head 74 to the light beam irradiation site in accordance with the recording signal. This allows
The direction of magnetization of the recording layer 78 is oriented in the direction of the modulation magnetic field, and overwriting can be performed. In this case, since the coercive force of the reproducing layer 79 is small, the magnetic domain corresponding to the magnetization of the recording layer 25
Is formed. As shown in FIG. 21, the shape of the magnetic domain is an arrow blade shape, and the length W _m is determined by the length W _m ′ of the modulation magnetic field. In other words, by switching the modulation magnetic field at high speed,
Magnetic domains of a length smaller than the light spot can be recorded.

By the way, as a method for reproducing a magnetic domain smaller than the light spot recorded as described above, a method shown in FIG. 22 (Optical Data Storage) is used.
Topical Meeting 1991.2.25
27, TuB3, TuB4) or the method shown in FIG. 23 (Nikkei Electronics 1991.3.4,
P92). In each of these methods, a part of the light spot is masked to reduce the reproducible area.
Hereinafter, the reproduction method will be described. First, the former reproduction method is used. In FIG. 22, (a) is a diagram showing a part of the magneto-optical recording medium viewed from the surface, and (b) is a diagram showing a magnetization state of each layer of the recording medium. The magnetic layer of the magneto-optical recording medium is composed of three layers, and 88 is a reproducing layer having a Curie temperature higher than 300 ° C. and a coercive force at room temperature of 100 (O
_e ) degree. Reference numeral 89 denotes a switching layer having a Curie temperature of about 120 ° C., and 90 denotes a recording layer having a Curie temperature of about 250 ° C. All of these have a coercive force at room temperature of greater than 10 ⁴ (O _e ). Here, the track 84
As shown in the figure, a reproducing light spot 85 (85 ') is irradiated as shown in the figure. At this time, assuming that the magneto-optical recording medium is moving in the direction B in the figure, the magnetic layer is first heated by the heat of the light spot 85. Heated. In this case, a region indicated by 86 (86 ') is a region where the temperature of the switching layer becomes higher than the temperature at which the magnetization of the switching layer disappears, and becomes a mask region for masking a part of the light spot. In the mask region 86 (86 '), the exchange coupling force between the reproducing layer and the recording layer is cut off, so that the magnet 9
When an external magnetic field is applied in the same direction of magnetization as the recording magnetic domain according to 1, the magnetization of the reproducing layer 88 in the mask region 86 (86 ') is always upward. Therefore, the light spot 85 (85 ')
Since the portion excluding the substantial mask area 92 becomes a reproducible area, the recording magnetic domain arrays 87-1 to 87-6 smaller than the original size of the light spot 85 (85 ') can be reproduced.

Next, the latter reproduction method will be described with reference to FIG. 23A is a diagram viewed from the surface of the magneto-optical recording medium, and FIG. 23B is a diagram illustrating the magnetization state of each layer. Here, the magnetic layer of the magneto-optical recording medium is composed of two layers, 96 is a reproducing layer, and 97 is a recording layer. Recording layer 97
Has a large coercive force and the same Curie temperature as a normal magneto-optical recording medium, but the reproducing layer 96 has characteristics in which both the coercive force and the Curie temperature are lower than those of the recording layer 97. Here, the track 84 is irradiated with a reproducing light spot 93 as shown in the figure. At this time, assuming that the magneto-optical recording medium is moving in the direction C in FIG. 98
, Only the reproducing layer 96 having a small coercive force is forcibly magnetized downward, and masks the recording pits 95-2 to 95-4 of the recording layer 97 which has been magnetized upward. At this time, the temperature rises in the irradiated portion of the light spot 93 (93 '), and the temperature of the region exposed to light for a long time becomes high. Therefore, the recording pits 95-5 to 95-6 of the recording layer 97 are reproduced by the exchange coupling force. Area 94 transferable to layer 96
(94 ') can be formed. Reference numeral 99 denotes an auxiliary magnet for assisting transfer. Therefore, a region indicated as 100 in the light spot 93 is a reproducible region. As described above, in any of the methods, the apparently effective light spot diameter can be reduced.

[0010]

However, in the conventional reproducing method shown in FIGS. 22 and 23, since the masked area is only the front side or the rear side of the light spot, the non-masked side of the light spot is used. As a result, there is a problem that the quality of the reproduced signal is deteriorated due to the influence of the above. In particular, in the reproducing method of FIG. 22, the recording pits 87-3 and 87-
There was a problem of being affected around 6. Further, in the reproducing method shown in FIG. 23, since an initialization magnet is required, there is a problem that the structure of the apparatus is complicated and large.

The present invention has been made in order to solve such a problem, and an object of the present invention is to reproduce a magnetic domain smaller than an optical spot with high quality and to perform direct verification simultaneously with recording. It is an object of the present invention to provide a magneto-optical recording medium, a magneto-optical recording method , and a magneto-optical reproducing method that are enabled.

[0012]

An object of the present invention is to provide a transparent substrate.
Plate, a regeneration layer, and exchange-coupled to the regeneration layer,
It has a lower Curie temperature and higher coercive force than the raw layer.
Curie temperature lower than the recording layer between the recording layer and
A temperature that exhibits in-plane magnetization at temperature and perpendicular magnetization at or above a predetermined temperature
Control layer is a reproduction layer, a control layer, a recording layer on the substrate in the order of
This is achieved by a magneto-optical recording medium characterized by being laminated .

It is another object of the present invention to provide a transparent substrate,
Layer and exchange-coupled to the regeneration layer and
Between low Curie temperature and recording layer with high coercive force
The Curie temperature is lower than that of the recording layer, and the
An adjustment layer that exhibits magnetization and becomes perpendicular magnetization at a predetermined temperature or higher,
The reproduction layer, the adjustment layer, and the recording layer were stacked in this order on the substrate.
Magneto-optical recording method for recording information on magneto-optical recording medium
The Curie temperature of the reproduction layer or less, and the adjustment layer
The medium is heated to a temperature above the Curie temperature of
The recording layer is irradiated with a recording light beam to
In addition to blocking the exchange coupling force,
Record information on the recording layer by applying an external magnetic field modulated by
And the magnetization of the reproducing layer is oriented in the direction of the external magnetic field,
This is achieved by a magneto-optical recording method , wherein verifying recorded information is performed using reflected light from the reproducing layer of the recording medium.

Further, an object of the present invention is to provide a transparent substrate,
Layer and exchange-coupled to the regeneration layer and
Between low Curie temperature and recording layer with high coercive force
The Curie temperature is lower than that of the recording layer, and the
An adjustment layer that exhibits magnetization and becomes perpendicular magnetization at a predetermined temperature or higher,
The reproduction layer, the adjustment layer, and the recording layer were stacked in this order on the substrate.
A magneto-optical reproducing method for reproducing information from a magneto-optical recording medium is described.
Irradiating the medium with a light beam for reproduction to record information on the recording layer.
Area where the information is transferred to the reproduction layer, and the transferable area
Exchange coupling force between the reproducing layer and the recording layer outside the region is weakened.
Forming a non-transferable area and applying the light beam
A magnetic field in a certain direction is applied to the vicinity of the transfer area to
To orient the magnetization in the predetermined direction by detecting the magnetized state of the transcription region from the reflected light of the light beam is achieved by the magneto-optical reproducing method characterized by reproducing the recorded information.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram showing one embodiment of the magneto-optical recording medium of the present invention. In FIG. 1, reference numeral 1 denotes a transparent substrate made of a light transmissive material such as glass or plastic. On this transparent substrate 1, a protective layer 2, a reproducing layer 3 (first magnetic layer), an adjusting layer 4 (third magnetic layer), a recording layer 5 (second magnetic layer), a protective layer 6, and a reflective layer 7
Are sequentially laminated. The reproducing layer 3 and the recording layer 5 are exchange-coupled, and the adjustment layer 4 provided therebetween functions to control the exchange coupling force by the temperature of the light beam. Reference numeral 8 denotes an objective lens for condensing a light beam necessary for actually recording and reproducing data on and from a magneto-optical recording medium, and 9 denotes a magnetic head arranged to face the same.

FIG. 2 is a characteristic diagram showing the relationship between the temperature and the coercive force of each of the above magnetic layers. 10 is a characteristic curve of the reproducing layer 3, 11 is a characteristic curve of the adjusting layer 4, and 12 is a characteristic curve of the recording layer 5. It is. The vertical axis in FIG. 2 indicates both the perpendicular magnetization state and the in-plane magnetization state.
Coercive force in the state of
The coercive force of the perpendicular magnetization and the coercive force of the in-plane magnetization for the adjustment layer
Show. As is apparent from FIG. 2, the reproducing layer 3 has a small coercive force H _C10 at room temperature and has a high Curie temperature T _C10 , and the recording layer 5 has a large coercive force H _C12 at room temperature and a low Curie temperature T _C12. Having. The coercive force H _C11 at room temperature and the Curie temperature T _C11 of the adjustment layer 4 are both smaller than the others. In the drawing, T _R denotes the temperature range of the magnetic layer in the vicinity of the optical spot for reproduction, above room temperature, the Curie temperature is less than the adjustment layer 4. Further, T _W is the temperature range of the magnetic layer near the light spot at the time of recording. In the vicinity of the Curie temperature T _C12 of the recording layer 5, it is higher than the Curie temperature T _C11 of the adjustment layer 4, and the Curie temperature T _{C10 of the} reproducing layer 3. It is smaller. here
The adjustment layer 4 is controlled from room temperature to the regeneration temperature as described later.
In-plane magnetization state to the degree T _R, the vertical at the regeneration temperature T _R or
Indicates the magnetization state. That is, the in-plane magnetization at regeneration temperature T _R or
Coercive force disappears. Table 1 shows the specific composition, film thickness, and other characteristics of the magneto-optical recording medium of this example.

[0017]

[Table 1] As shown in Table 1, the reproducing layer 3 has a composition of, for example, TM-rich, and Ms (saturation magnetization) is 200 emu / c.
c or less. The adjustment layer 4 has a composition of, for example, RE-rich, and Ms is about 300 to 400 emu / cc. The recording layer 5 is, for example, a TM-
rich, but Ms is 200 emu / cc
Or less, or -200 emu / cc or more.

Next, the exchange coupling force between the reproducing layer 3 and the recording layer 5 and the function of the adjusting layer 4 will be described. First, below the temperature range T _R during reproduction, Ms of the adjustment layer 4 is large and the value of 2πMs ² is larger than the anisotropy constant, so that the adjustment layer 4 has in-plane magnetization instead of perpendicular magnetization. . Therefore, the exchange coupling force between the reproducing layer 3 and the recording layer 5 is weakened. That is, the external magnetic field H larger than the coercive force of the reproducing layer 3
_{When ex} is applied, the magnetization of the reproducing layer 3 is directed to the direction of the external magnetic field. When the temperature of the magnetic layer to a temperature range T _R at the time of reproduction is increased, anisotropy constant adjustment layer 4 is 2πMs at that temperature
^Since the value is larger than ² , the adjustment layer 4 has perpendicular magnetization. As a result, the exchange coupling force between the reproducing layer 3 and the recording layer 5 is increased, and the magnetization direction recorded on the recording layer 5 can be transferred to the reproducing layer 3. Furthermore, when the temperature of the magnetic layer rises to the temperature range T _W at the time of recording, the temperature of the adjustment layer 4 becomes _{equal to} or higher than the Curie temperature T _C11 , so that the magnetization disappears.
Therefore, the exchange coupling force between the reproduction layer 3 and the recording layer 5 is cut off, and when an external modulation magnetic field ± H _ex that is larger than the coercive force of the reproduction layer 3 is applied, the magnetization of the reproduction layer 3 becomes smaller than the external modulation magnetic field. Orientation.

Here, a method for recording and reproducing information on the magneto-optical recording medium will be described in detail with reference to FIGS. First, as an optical head and a magnetic head necessary for recording information, those equivalent to those shown in FIG. 13 will be used. FIG. 3A is a diagram showing a part of the magneto-optical recording medium viewed from the surface, and FIG. 3B is a diagram showing a state of magnetization of each magnetic layer. In FIG. 1, reference numeral 13 denotes a track on the magneto-optical recording medium on which information is recorded. It is assumed that the magneto-optical recording medium is moving in the direction A in the figure. 14
(14 ') indicates a recording light spot irradiated on the track 13, that is, an area irradiated with the light spot during recording. This light spot is obtained by irradiating a light beam of a light source such as a semiconductor laser with the objective lens 8 shown in FIG. 1 and irradiating the light beam. The light spot 14 raises the temperature of the magnetic layer. Reference numeral 16 (16 ') denotes an exchange coupling force blocking region in the temperature range of _TW shown in FIG. In the exchange coupling force blocking region 16, the magnetization of the adjustment layer 4 disappears, and the exchange coupling force between the reproducing layer 3 and the recording layer 5 is blocked. 15 (1
5 ') is a region on the high temperature side of the temperature range of T _W , which is a recordable region in which the magnetization of the recording layer 5 can be reversed by the external modulation magnetic field ± H _ex applied from the magnetic head 9 shown in FIG. It is.

When recording information, by irradiating the light spot 14 with a constant power while scanning as described above, a recordable area 15 and an exchange coupling force blocking area 16 including these light spot 14 and the recordable area 15 are recorded. To form Then, by the magnetic head 9 follow the I information to be recorded in this state by modulating the external magnetic field + H _ex or -H _ex, and applies the magnetic field in a region generally including the exchange coupling force shielding region 16. As a result, a magnetic domain is recorded in the recordable area 15 of the recording layer 5, and the magnetic domain to be overwritten has the same shape as the conventional magnetic field modulation overwrite method.
That is, as shown in FIG. 3, since the new information is overwritten from above the magnetic domain 17-1 of the previous information, the shape of the magnetic domain 17-2 of the new information has an arc shape at the leading and trailing ends of the magnetic domain. It becomes an arrow feather shape. In this case, by increasing the modulation frequency of the external magnetic field, the length of the magnetic domain to be recorded in the direction A can be made approximately equal to the radius of the light spot 14. On the other hand, the direction of the magnetization of the reproducing layer 3 in the exchange coupling force blocking region 16 changes in accordance with the modulation of the external magnetic field. That is, the recording layer 5
Orientation is performed in the same direction as the direction of the magnetic domain that overwrites the magnetic domain. Thereby, by detecting the polarization state of the reflected light from the magneto-optical recording medium with the reproducing optical system of the optical head,
The direction of the magnetization of the reproducing layer 3 can be detected. That is,
It is possible to check whether or not the magnetic domain has been damaged due to a defect of the magnetic layer or the like, and it is possible to perform direct verification at the same time as recording with one light spot.

Next, a method of reproducing information recorded on the magneto-optical recording medium will be described. FIG. 4A is a diagram showing a part of the magneto-optical recording medium viewed from the surface, and FIG. 4B is a diagram showing the state of magnetization of each magnetic layer. In FIG. 1, reference numeral 13 denotes a track on the magneto-optical recording medium on which information is recorded.
It is assumed that the magneto-optical recording medium is moving in the direction A. 1
Reference numeral 8 (18 ') denotes an area irradiated with a reproduction light spot having a lower power than the recording light beam. The light spot 18 raises the temperature of the magnetic layer. 19 (19 ') is a transcription region on the temperature range of T _R shown in FIG. In the transferable area 19, the adjustment layer 4 has perpendicular magnetization, and the exchange coupling force between the reproduction layer 3 and the recording layer 5 is strengthened. Therefore, the adjustment layer 4 is not affected by the external magnetic field applied by the magnetic head 9, and The direction of the magnetization is transferred as the direction of the reproducing layer 3. Reference numeral 20 (20 ') denotes a non-transferable area outside the transferable area 19 and including the light spot 18. Temperature of the magnetic layer of the transfer-prohibited areas 20 is equal to or less than the temperature range of T _R. In this region 20, the adjustment layer 4 has in-plane magnetization, the exchange coupling force between the reproduction layer 3 and the recording layer 5 is weakened, and the magnetization direction of the reproduction layer 3 is independent of the magnetization direction of the recording layer 5, It follows the direction of the external magnetic field from the magnetic head 9.
At this time, the magnetic head 9 applies an external magnetic field in a predetermined fixed direction.

As described above, at the time of reproduction, the light spot 18 having a constant power lower than the power at the time of recording is irradiated while scanning, thereby forming a transferable area 19 and a non-transferable area 20. In this state, the magnetic head 9 applies an external magnetic field in a certain direction to an area including the non-transferable area 20. The direction of the external magnetic field may be the same as the direction of the magnetization of the recording layer 5 at the time of initialization, or vice versa. As a result, of the magnetic domains 21 on the track 13, 21-2, 21-4 and 21- which have entered the non-transferable area 20.
3 are masked, and only the solid line portions of the magnetic domains 21-3 appearing in the transferable area 19 contribute to the change in the polarization state of the reproduction reflected light. Therefore, the reflected light is used to reproduce the optical system 49 of the optical head as shown in FIG.
By detecting, by detecting its polarization state,
The direction of the magnetic domain in the transferable area 20 of the reproducing layer 3 can be detected, and the magnetic domain having a length equal to or less than the diameter of the light spot 18 can be reproduced. In this embodiment, since the area to be masked surrounds the area (transferable area 19) contributing to the change in the polarization state of the reproduction reflected light, FIG. 22 and FIG.
As compared with the conventional mask method shown in (1), the influence of surrounding magnetic domains is less, and a reproduced signal having a high C / N can be obtained. Although it is possible to reproduce a magnetic domain having a smaller length by making the transferable area 19 smaller, the transferable area 1 is considered in consideration of the C / N of the reproduced signal.
The size of 9 is preferably about half the size of the reproduction light spot 18.

Further, description of the reproducing method will be continued. Here, it is assumed that half of the light spot 18 is masked for the sake of simplicity. In this state, the transferable area 1
How the phase distribution and the intensity distribution of the reflected light change when the magnetization direction in 9 is different from the magnetization direction in the masked region will be described with reference to FIGS.
FIG. 5 shows the reproducing layer 3 and the objective lens 45 in the optical head. The hatched portion of the reproducing layer 3 (the portion where the left half of the light spot is affected) is a mask region, which is fixed here as downward magnetization. The other part of the reproducing layer 3 (the part where the right half of the light spot is affected) is a transferable area, (a) when the magnetization in the same direction as the mask area is transferred, and (b) in a different direction. The case where the magnetization is transferred is shown. FIG. 6 shows the amplitude and intensity distribution of the reflected light of both. Here, similarly to FIG. 14, incident light is linearly polarized light polarized in the P-axis direction, reflected light for downward magnetization is R ₊ rotated + θ _k , and reflected light for upward magnetization is R ₋ rotated -θ _k. . Therefore,
The P-axis component and the S-axis component are (P ₊ , S ₊ ),
(P _+, S _-) to become.

First, considering the P-axis component, FIG.
In both (a) and (b), P ₊ is almost unchanged.
Therefore, the distribution of the amplitude of the reflected light (ignoring the size and seeing only the shape) is as shown in FIG. 6A, and the distribution of the light intensity (ignoring the size and seeing only the shape) ) Is FIG. 6 (b)
As shown in FIG. Next, as for the S-axis component, since the distribution of S ₊ is uniform in the light spot in FIG. 5A, the distribution of the amplitude of the reflected light (ignoring the size and seeing only the shape) And the distribution of light intensity (ignoring the size and seeing only the shape) is similar to the P-axis component in FIG.
(A) and (b). However, since FIG. 5 (b) the magnetic domain boundaries is within the light spot, S ₊ and S _- 2
There are two components. S ₊ and S _- are components having the same magnitude and a phase shift of π. At this time, the distribution of the amplitude of the reflected light (ignoring the size and looking at the shape only) and the distribution of the light intensity (ignoring the size and looking at the shape only) are shown in FIG. It becomes like d).

Next, the S-axis component light will be described in more detail with reference to FIGS. FIG. 7 shows the distribution of light intensity on the magneto-optical recording medium surface and the photodetector surface in the parallel light beam when all the magneto-optical recording media as shown in FIG. ing. However, the stereoscopic views shown here are standardized by the maximum value in each case, and do not correspond to the size. The same applies to the following description. Light emitted from the semiconductor laser of the optical head passes through a collimator lens, a beam shaping prism, and the like, and becomes a parallel light beam having a Gaussian distribution. The diameter of the parallel light beam is about 6 mm, and the diameter of the opening of the optical head is 4 mm.
Then, the intensity distribution of the incident parallel light beam is the distribution shown in 22 stereoscopic views. When this parallel light beam is condensed by the objective lens 26 and irradiated on the surface of the magneto-optical recording medium as a light spot having a diameter of about 1 μm, the light intensity distribution at this time becomes a distribution shown by 23. At the incident parallel light beam 22 and the medium surface 23, only the light of the P-axis component has not yet generated the light of the S-axis component. The light reflected from the magneto-optical recording medium has an S-axis component due to the optical Kerr effect or the like. Here, since the magneto-optical recording medium has a uniform downward magnetization, S ₊ light is generated. The reflected light from the medium surface passes through the objective lens 26 again to become a reflected parallel light beam. Numeral 24 indicates the intensity distribution of the reflected parallel light beam, and both the P-axis component and the S-axis component have the same shape as the incident parallel light beam. The reflected parallel light beam is condensed by the condensing lens 27 and is irradiated on the photodetector surface. Numeral 25 indicates the light intensity distribution on the photodetector surface. Here, both the P-axis component and the S-axis component have the same shape as the intensity distribution on the medium surface.

FIG. 8 is a view showing the intensity distribution of the light of the S-axis component on the photodetector surface when the light spot 18 scans the magnetic domain 21 (here, one having an upward magnetization). The P-axis component is as shown in FIG. FIG. 8 (a)
(G) are diagrams showing the relative positions of the magnetic domain 21 recorded on the track 13 and the reproduction light spot irradiated on the track 13 little by little. The range indicated by 19 is a transferable area, and the range indicated by 20 is a non-transferable area. The magnetization of the non-transferable area 20 is downward,
The magnetic domains in that region are indicated by dashed dashed lines (21a). The magnetic domains in the transferable area 19 are indicated by solid oblique lines (21b). The numerical values shown in the figure are the values of the total amount of light. FIG. 8A shows the magnetic domain 2 in the transferable area 19.
In the case where there is no 1 (the state of FIG. 5A), the intensity distribution of the light of the S-axis component on the photodetector surface is the same as that indicated by 25 in FIG. The total light amount at this time is set to 100. And
As shown in FIGS. 8B, 8C, and 8D, when the proportion of the magnetic domains 21 occupying the transferable area 19 sequentially increases,
Eventually, as shown in FIG. 8E, the entirety of the transferable area 19 is occupied by the magnetic domain 21. This state is shown in FIG.
It corresponds to the state of. On the other hand, when looking at the light intensity distribution, as the ratio of the magnetic domains 21 occupying the transferable area 19 increases, the peak of the light spot sequentially shifts from the center of the optical axis, and the second peak centers on the optical axis. Appears on the opposite side of the first peak. FIG. 8E shows a state in which the light amounts of the two spots are equal. Further, as the magnetic domain 21 passes, the second peak becomes smaller as shown in FIGS. 8F and 8G, returns to one spot again, and returns to the state of FIG. 8A. In addition, the total light quantity decreases gradually and returns to 100 again.

The above first peak of the spot corresponds to the S _+, the second peak of the spot S _- corresponding to.
When these lights are detected by the reproduction optical system 49 in FIG.
The signal is as shown in FIG. FIG. 9A shows an arrangement of magnetic domains on an information track, and FIG. 9B shows a reproduced signal when the magnetic domain is detected by a general reproducing optical system 49. If the magnetic domain is reproduced by the conventional reproducing optical system, the two peaks shown above are received by the single photodetectors 53 and 54, respectively, so that S ₊ and S _- are canceled. Further, assuming that E ₀ is a reference level in FIG. 9B, in a state where there is no magnetic domain (a state of FIG. 5A), E ₊
The amplitude of the reproduced signal fluctuates up to that. On the other hand, in the state where the magnetic domain exists (the state of FIG. 5B), the S-axis component is canceled, and the amplitude of the reproduced signal does not fluctuate to E ₋ . Of course, information can be obtained from a reproduced signal as shown in FIG. 9B, but in order to improve the quality of the reproduced signal, FIG.
As shown in FIG. 5, a reproduced signal having an amplitude of almost zero level when there is no magnetic domain and having an amplitude of E ₊ 'is desirable when there is a magnetic domain.

An example of an apparatus for obtaining a reproduced signal as shown in FIG. 9C will be described with reference to FIGS. 10, 28, 29, and 30 correspond to 50, 51, and 52 shown in FIG. 13, respectively.
28 is a half-wave plate, 29 is a condenser lens, and 30 is a polarizing beam splitter. Numerals 31 and 32 denote two-divided photodetectors whose division lines are in directions corresponding to the directions orthogonal to the tracks of the magneto-optical recording medium. That is, when the track is projected onto the two-segment detector using the optical head, the dividing line is orthogonal to the track. 3
Reference numerals 3, 34 and 35 are amplifiers for differential detection, and reference numeral 36 is a reproduced signal. Reference numerals 37 and 38 denote amplifiers for detecting the sum signal. The differential signal 39 differentially detects the sum signal to obtain a reproduction signal 40. The reproduction signal 40 is equivalent to a reproduction signal obtained by a conventional reproduction optical system. In this embodiment, the direct verification at the time of information recording is performed using the reproduction signal 40 as described above.

FIG. 11 is a view showing an intensity distribution obtained on a two-divided detector as a result of superposing the P-axis component light on the S-axis component light shown in FIG. 8 and causing polarization interference. FIG. 11 (a),
FIG. 11B shows the two-divided photodetector 31 and FIG.
(C) and (d) show the two-divided photodetector 32. The X axis indicates the position on the two-segment photodetector shown below, and the Y axis indicates the magnitude of the intensity. This Y axis is located on the dividing line of the two-part photodetector. Next, when there is no magnetic domain 21 in the transferable area 19 (FIG. 5A), the distribution of the light intensity on the two-divided photodetectors 31 and 32 is shown in FIG.
The distribution is as shown in (a) and (c). At this time, the shape of each distribution is symmetric with respect to the Y axis, and the peak of the intensity is on the Y axis. The magnitude of this peak is shown in FIG.
FIG. 11A is larger than FIG. in this case,
Since the detection signals obtained by the individual photodetectors 31-1 and 31-2 and the photodetectors 32-1 and 32-2 of the two-split photodetectors 31 and 32 are the same, the differential detection amplifier 3
The signals obtained by differential detection at 3 and 34 are both 0. Therefore, the signal obtained by the differential detection amplifier 35 is also 0.

On the other hand, when the magnetic domain 21 is present in the transferable area 19 (FIG. 5B), the distribution of the light intensity on the two-divided photodetectors 31 and 32 is shown in FIGS. 11B and 11D. It becomes such a distribution. The peak of the distribution is divided into the + side and the − side of the X axis centering on the Y axis, and the magnitude of the peak is larger on the − side in FIG. 11B and larger on the + side in FIG. Become. Therefore, the photodetectors 31-1, 31-
When the differential detection of the signal 2 is performed, a signal having a negative value is obtained. When the differential amplifier 34 differentially detects the signal of the photodetectors 32-1 and 32-2, a signal having a positive value is obtained. Further, since the differential amplifier 35 differentially detects the output signals of the differential amplifier 34 and the differential amplifier 33, a signal having a positive value is obtained. Assuming that the peak of the signal at this time is E ₊ ′, the reproduced signal 36 for the magnetic domain shown in FIG. 9 is as shown in FIG. 9C, and the signal quality can be improved as compared with the conventional case.

FIG. 8 shows the light intensity distribution near the re-imaging point of the condenser lens 27. FIG. 12 shows the light intensity distribution at a position shifted from the re-imaging point on the optical axis. Is shown. In FIG. 12, when a magnetic domain appears in the transferable area 19, the peak is split into two, and the center gradually becomes concave. This 2
The magnitudes of the two peaks are approximately equal. Also, one of the peaks corresponding to R _+, and the other R _- corresponds to. The center part is a mixture of both. In order to reproduce the magnetic domains, the reproducing apparatus shown in FIG.
A signal similar to the reproduced signal shown in (c) can be obtained. However, in this case, the two-divided photodetectors 31 and 32 are arranged shifted from the focal position of the condenser lens 29 on the optical axis. Further, in order to improve the quality of the reproduction signal, a phase compensator such as a wave plate may be arranged in the light beam of the reproduction optical system shown in FIG. The numerical values in the figure indicate the total amount of light.

[0032] Incidentally, an example of the magneto-optical recording medium of the present invention in Table 1, as a specific material Besides the magnetic layers, non by each of one or more combinations of transition metal and rare earth metal A crystalline alloy can be used. For example, the transition metals mainly include Fe, Co, and Ni, and the rare earth metals include Gd, Tb, Dy, Ho, Nd, and Sm. Typical combinations include TbFeCo, Gd
TbFe, GdFeCo, GdTbFeCo, GdDy
FeCo and the like.

[0033]

As described above, the present invention has the following effects.

(1) Reproducing layer and recording layer exchange-coupled to it
Adjustment to adjust the exchange coupling force between the reproducing layer and the recording layer
Adjustable by irradiating the recording light beam with the layer
By exchanging the exchange coupling force between the reproducing layer and the recording layer by eliminating the magnetization of the layer , it is possible to perform verification using the reflected light of the recording light beam from the reproduction layer, that is, to perform direct verification simultaneously with recording. Can be.

(2) Reproducing layer by irradiation of reproducing light beam
And a transferable area having an increased exchange coupling force between the recording layer and the recording layer , and a non-transferable area outside the exchange coupling force having a weaker exchange coupling force, and
By applying a magnetic field in a certain direction near the light beam irradiation part and masking the information of the non-transferable area, only the magnetic domains in the transferable area can be reproduced, and the magnetic domains smaller than the diameter of the light spot can be reproduced. .

(3) In addition, since the transferable area is surrounded by the masked area, the influence of surrounding magnetic domains as seen in the conventional mask method can be effectively reduced, and C / C A reproduced signal with a high N can be obtained.

(4) Since no initialization magnet is required, the configuration of the apparatus is not complicated and the size is not increased.

[0038]

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a magneto-optical recording medium according to the present invention.

FIG. 2 is a diagram showing characteristics of each magnetic layer of the magneto-optical recording medium of the embodiment of FIG.

FIG. 3 is a diagram showing an information recording process according to the magneto-optical recording method of the present invention.

FIG. 4 is a diagram showing an information reproducing process according to the magneto-optical reproducing method of the present invention.

FIG. 5 is a diagram showing magnetization of a reproduction layer at the time of information reproduction by a transferable region and a mask region.

6 is a diagram showing an amplitude distribution and an intensity distribution of reflected light for a P-axis component and an S-axis component, respectively, corresponding to the transferable area and the mask area of FIG. 5;

FIG. 7 is a diagram showing a light intensity distribution on a magneto-optical recording medium surface and a photodetector surface in a parallel light beam when all magneto-optical recording media have downward magnetization.

FIG. 8 is a diagram showing a light intensity distribution and a change in the total light amount when the ratio of a magnetic domain in a transferable area is changed during scanning of a reproduction light spot.

FIG. 9 is a diagram showing a magnetic domain on an information track, a reproduced signal reproduced by a conventional reproducing method , and a reproduced signal reproduced by a reproducing method of the present invention.

FIG. 10 is a diagram showing an example of an information reproducing system according to the magneto-optical reproducing method of the present invention.

FIG. 11 is a diagram illustrating an intensity distribution of light obtained on a two-segment photodetector when light of a P-axis component is superimposed on light of an S-axis component to cause polarization interference.

FIG. 12 is a diagram showing a state of a change in a light intensity distribution and a total light amount when the reproduction light spot is shifted from a re-imaging point on the optical axis during scanning.

FIG. 13 is a diagram showing an optical system of a general magneto-optical recording / reproducing apparatus.

FIG. 14 is a diagram for explaining the principle of information reproduction to be reproduced as a magneto-optical signal in magneto-optical recording.

FIG. 15 is a diagram showing a schematic configuration of a magneto-optical recording device in a light modulation system.

FIG. 16 is a diagram showing characteristics of a magneto-optical recording medium used in a light modulation method.

FIG. 17 is a time chart showing the relationship among a light spot, its light intensity, a bias magnetic field, and recorded magnetic domains in the light modulation method.

FIG. 18 is a diagram showing a temperature distribution due to light spot irradiation and recording pits to be recorded in the light modulation method.

FIG. 19 is a diagram showing a schematic configuration of a magneto-optical recording device in a magnetic field modulation system.

FIG. 20 is a diagram showing characteristics of a magneto-optical recording medium used in a magnetic field modulation system.

FIG. 21 is a time chart showing the relationship among a light spot, its light intensity, a modulation magnetic field, and a recorded magnetic domain in a magnetic field modulation method.

FIG. 22 is a diagram showing an example of a conventional reproducing method for reproducing a magnetic domain smaller than a recording light spot.

FIG. 23 is a diagram showing another conventional reproducing method.

[Explanation of symbols]

 Reference Signs List 1 transparent substrate 3 reproduction layer (first magnetic layer) 4 adjustment layer (third magnetic layer) 5 recording layer (second magnetic layer) 8 objective lens 9 magnetic head 13 track 14 recording light spot 15 recordable area Reference Signs List 16 Exchange coupling cutoff area 18 Light spot for reproduction 19 Transferable area 20 Nontransferable area 30 Polarization beam splitter 31, 32 Two-part photodetector 33, 34, 35, 39 Differential amplifier 37, 38 Adder

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ identification code FI G11B 11/105 586 G11B 11/105 586S (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B 11/105

Claims (6)

(57) [Claims] 1. A transparent substrate, a reproducing layer, and exchange with the reproducing layer.
Bonding and a lower Curie temperature than the regeneration layer;
Between the recording layer having high coercive force and the recording layer
Temperature is low and shows in-plane magnetization at room temperature
An adjustment layer that becomes perpendicular magnetization on the above, a reproduction layer on the substrate,
A magneto-optical recording medium characterized in that an adjustment layer and a recording layer are laminated in this order . 2. A transparent substrate, a reproducing layer, and exchange with the reproducing layer.
Bonding and a lower Curie temperature than the regeneration layer;
Between the recording layer having high coercive force and the recording layer
Temperature is low and shows in-plane magnetization at room temperature
An adjustment layer that becomes perpendicular magnetization on the above, a reproduction layer on the substrate,
Information is recorded on the magneto-optical recording medium laminated in the order of the adjustment layer and the recording layer.
In the magneto-optical recording method for recording data, the temperature of the reproducing layer is equal to or lower than the Curie temperature and the key of the adjusting layer is adjusted.
To raise the temperature of the medium to a temperature equal to or higher than the
Irradiating a recording light beam to exchange the light between the reproducing layer and the recording layer;
As well as interrupting the resultant force, it changes according to the information signal to be recorded.
Recording information on the recording layer by applying a regulated external magnetic field, and
Orienting the magnetization of the reproducing layer in the direction of the external magnetic field,
A magneto-optical recording method for verifying recorded information using reflected light from the reproducing layer . 3. A transparent substrate, a reproducing layer, and exchange with the reproducing layer.
Bonding and a lower Curie temperature than the regeneration layer;
Between the recording layer having high coercive force and the recording layer
Temperature is low and shows in-plane magnetization at room temperature
An adjustment layer that becomes perpendicular magnetization on the above, a reproduction layer on the substrate,
Information is obtained from the magneto-optical recording medium laminated in the order of the adjustment layer and the recording layer.
In the magneto-optical reproducing method for reproducing information, the information on the recording layer is reproduced by irradiating the medium with a reproducing light beam.
A transferable area transferred to the raw layer and an area outside the transferable area
In which the exchange coupling force between the reproducing layer and the recording layer on the side is weakened.
Forming a non-photographable area and near the light beam irradiation part
And applying a magnetic field in a certain direction to the magnetization of the non-transferable area.
Said predetermined direction is aligned, by detecting the magnetized state of the transfer region from the reflected light of the light beam, the magneto-optical reproducing method characterized by reproducing recorded information. Wherein said transfer area is serial to claim 3, characterized in that the size of about half of the reproducing light spot
Magneto-optical reproducing method of mounting. 5. The reflected light of the reproduction light beam is divided into two light beams, and the two light beams are detected by a two-division sensor having a division line in a direction orthogonal to the scanning direction of the light beams. the sensor outputs of the two-split sensors each detect the differential, by detecting the differential detection output, which is the obtained further differential, to claim 3, characterized in that to generate a reproduced signal of the recorded information The magneto-optical reproducing method described in the above . 6. The reflected light of the recording light beam is split into two light beams, and each of the two light beams is detected by a two-split sensor having a split line in a direction orthogonal to the scanning direction of the light beam. to generate each of the sum signal of the respective sensor outputs of the two-split sensor, by detecting the differential of the sum signal which is the obtained, according to claim 2, characterized in that to generate a reproduction signal for verification Magneto-optical recording method .