JP2001134996A - Magneto-optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magneto-optical recording medium in which extremely minute recording marks of <=0.2 μm size can be accurately formed. SOLUTION: In the magneto-optical recording medium for MAMMOS, the compositions of magnetic materials are controlled in such a manner that the magnetic material constituting a magnetic domain enlarging and reproducing layer has the compensation temperature higher than room temperature and has the Curie temperature Tcr lower than the Curie temperature Tcw of the magnetic material constituting a recording layer. Thereby, the saturation magnetization in the magnetic domain enlarging and reproducing layer disappears in the recording temperature region during recording information. As a result, minute marks as <=0.2 μm in size, for example, can be accurately formed in the recording layer. Or by forming a leak magnetic field controlling layer having higher Curie temperature than that of the recording layer, changes in the leaked magnetic field of the recording layer with temperature can be suppressed to increase the power margin for reproducing light.

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 having a recording layer and a magnetic domain enlarging and reproducing layer in which magnetic domains of the recording layer are transferred and enlarged. The present invention relates to a magneto-optical recording medium for ultra-high-density recording capable of stably forming various recording magnetic domains.

[0002]

2. Description of the Related Art A magneto-optical recording medium such as a magneto-optical disk is known as an external memory of a computer or the like. Magneto-optical recording media are widely used as recording media in the multimedia era because information can be rewritten and large-capacity data such as moving images and audio can be handled. In recent years, it has been desired to further increase the storage capacity of a magneto-optical recording medium. As a method for achieving this, for example, it is conceivable to record information at a high density by making the recording magnetic domains formed in the recording layer smaller. It is possible to use a light pulse magnetic field modulation method for applying a magnetic field having a polarity corresponding to a recording signal while irradiating a pulsed light in synchronization with a recording clock while recording the recording magnetic domain in a miniaturized manner.

However, when the recording magnetic domains are miniaturized, a plurality of recording magnetic domains are included in the light spot, and it becomes difficult to reproduce them individually. As a method for solving this problem, for example, a magnetic domain expansion reproduction method (MAMMOS;
Magnetic Amplifying Magneto-Optical System) has been proposed. In this MAMMOS, at the time of reproduction, at least one of a laser beam and an external magnetic field is modulated and applied, so that a recording mark (recording magnetic domain) formed on the information recording layer is transferred to the magnetic domain enlarged reproduction layer and transferred. The magnetic domain is expanded by the magnetic domain expansion reproducing layer by an external magnetic field. Since the amplified reproduction signal is detected from the magnetic domain expanded by the magnetic domain expansion reproduction layer, even if a minute recording mark is formed on the recording layer, it can be reproduced with a sufficient signal intensity. The applicant discloses in WO 98/02878 a magneto-optical recording medium according to such a MAMMOS.

[0004]

In order to further increase the density of a magneto-optical recording medium, it is conceivable to form smaller recording marks on a magneto-optical recording medium having a reproducing layer such as a MAMMOS. . According to the study of the present inventors, it is difficult to accurately form such a minute recording mark in a desired shape and at a desired position even when trying to form a minute recording mark of, for example, 0.2 μm or less. all right. Observation of the formed minute recording marks revealed that the outline was unclear.

Further, according to the study of the present inventors, MA
When reproducing information by irradiating a magneto-optical recording medium having a reproducing layer with reproducing light, such as an MMOS, it is necessary to control the power of the reproducing light to a relatively narrow power range. Was not secured.

Japanese Patent Application Laid-Open No. H10-289497 discloses a magneto-optical recording medium having an amplification layer and a recording layer, in which a recording magnetic domain of the recording layer is transferred and enlarged to the amplification layer for reproduction. This publication states that the amplification layer has a lower Curie temperature than the recording layer in order to sufficiently improve the reproduction signal intensity, but the amplification layer must not have a compensation temperature higher than room temperature. It has been. The publication does not suggest or disclose the magneto-optical recording medium of the present invention.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and a first object of the present invention is to provide a magneto-optical recording device capable of reliably forming an extremely fine recording mark having a clear contour. To provide a medium.

A second object of the present invention is to provide a magneto-optical recording medium having an expanded power margin of the reproduction light.

[0009]

According to a first aspect of the present invention, there is provided a magneto-optical recording medium, comprising: a recording layer on which information is recorded; and a magnetic domain from which a magnetic domain is transferred from the recording layer. Wherein the Curie temperature of the magnetic domain expansion reproduction layer is lower than the Curie temperature of the recording layer, and the magnetic domain expansion reproduction layer has a compensation temperature in the range of room temperature to 200 ° C. A medium is provided.

In the magneto-optical recording medium according to the first aspect of the present invention, the magnetic domain enlarging and reproducing layer has a compensation temperature of room temperature to 200 ° C. and a Curie temperature lower than the Curie temperature of the recording layer. Recording marks can be stably recorded. The reason will be described below. According to the study of the present inventors, in a conventional magneto-optical recording medium, the reason why an ultra-fine recording mark having a recording mark length of, for example, 0.2 μm or less cannot be formed stably is that a magnetic domain is generated during recording. It was found that the saturation magnetization (Ms) of the enlarged reproducing layer affected the recording layer. That is, in the conventional magneto-optical recording medium, as shown in FIG. 5, the Curie temperature Tcr of the magnetic domain expansion reproducing layer is higher than the Curie temperature Tcw of the recording layer. , The saturation magnetization Ms of the magnetic domain expansion reproducing layer appears with a considerable size. For this reason, when the medium is heated to the vicinity of the Curie temperature Tcw of the recording layer during information recording, a considerable amount of saturation magnetization of the magnetic domain enlarging and reproducing layer is generated, which adversely affects the recording magnetic field and forms a recording magnetic domain. It is thought that it prevented. On the other hand, in the magneto-optical recording medium of the present invention, since the saturation magnetization of the magnetic domain expansion reproducing layer has the temperature dependence as shown in FIG. 1, the saturation magnetization of the magnetic domain expansion reproducing layer disappears in the recording temperature region. As a result, a minute recording magnetic domain can be stably formed on the recording layer. In the present specification, the magnetic domain expansion reproduction layer means a layer in which magnetic domains are transferred from a recording layer and the transferred magnetic domains are expanded, and an alternating magnetic field, a DC magnetic field, and an alternating magnetic field are used to expand the transferred magnetic domains.
An arbitrary external field such as light or heat may be applied, and a case where the magnetic domain is expanded based on the magnetic characteristics of the enlarged reproduction layer without applying the external field is also included.

In the present invention, the relationship between the Curie temperatures of the reproducing layer and the recording layer formed on the substrate is as follows.
For example, it can be determined by comparing the laser power when the recording layer reaches the Curie temperature with the laser power when the magnetic domain expansion reproducing layer reaches the Curie temperature. In order to determine the laser power when the recording layer reaches the Curie temperature, the laser power when the recording mark disappears may be determined. Normally, when the recording mark of the recording layer is irradiated with a high-power laser beam without applying an external magnetic field and heated to the Curie temperature or higher without applying an external magnetic field, the region where the recording mark of the recording layer is formed is arbitrary. In which the magnetization is oriented. In this specification,
This phenomenon is called the disappearance or destruction of the recording mark.

The laser power P1 when the temperature reaches the Curie temperature of the recording layer can be determined, for example, as follows. First, an M with a recording layer and a magnetic domain expansion reproducing layer
A recording mark is recorded on a magneto-optical recording medium for AMMOS. First, the magneto-optical recording medium on which the recording marks are formed is irradiated with a laser beam having a laser power Px higher than the normal reproducing power (first step). Next, the power of the laser beam is returned to the normal reproduction power, an alternating magnetic field is applied, and MAMMOS reproduction is performed (second step). MAMMO
When the power Px of the laser beam irradiated before the S reproduction is lower than the laser power P1 that reaches the Curie temperature of the recording layer, the recording magnetic domain of the recording layer has not disappeared.
A reproduction signal is detected from the magnetic domain expansion reproduction layer according to the reproduction principle of AMMOS. Next, the first step and the second step (MAMMOS reproduction) are repeated in the same manner as described above while gradually changing the laser power Px in the first step. First
When the laser power Px of the laser light in the process reaches a certain value, the recording layer is heated to the Curie temperature by the heat of the laser light, and the recording mark formed on the recording layer disappears, and the second mark is formed.
The reproduced signal in the process is not detected. This makes it possible to obtain the laser power at which the recording mark disappears, that is, the laser power P1 when the Curie temperature of the recording layer is reached.

On the other hand, a method for obtaining the laser power P2 when the temperature reaches the Curie temperature of the magnetic domain expansion reproducing layer is as follows. First, in the state where no recording mark is formed on the recording layer, normal MAMMOS reproduction is performed by irradiating a laser beam while applying an alternating magnetic field. If the laser power applied to the medium is within the reproduction power margin used in normal MAMMOS reproduction, no reproduction signal is detected because no recording mark exists on the recording layer. But,
When the laser power exceeds the read power margin, the magnetization of the magnetic domain expansion read layer follows the alternating magnetic field applied to the medium, and a read signal is detected. Since the Kerr rotation angle (θk) of the magnetic domain enlarging reproducing layer has a temperature dependency as shown in FIG. 3, if the laser power is increased to further heat the magnetic domain enlarging reproducing layer, the detected reproduction signal amplitude It gets smaller gradually. When the laser power is further increased, the magnetic domain expansion reproducing layer is heated to the Curie temperature Tc by the heat of the laser beam.
r, the reproduction signal is no longer detected from the magnetic domain expansion reproduction layer. That is, the laser power at this time is
This is the laser power P2 when the Curie temperature of the magnetic domain expansion reproducing layer is reached. By comparing the magnitudes of the laser powers P1 and P2 obtained as described above, the magnitude relation between the Curie temperatures of the recording layer and the magnetic domain expansion reproducing layer can be understood.
According to this method, even when the recording layer and the magnetic domain expansion reproducing layer are stacked on the substrate, the magnitude relationship between the Curie temperatures can be obtained.

The magneto-optical recording medium according to the first aspect of the present invention comprises:
Further, an auxiliary magnetic layer made of a material having a Curie temperature higher than the Curie temperature of the recording layer and having a saturation magnetization that decreases as the temperature rises within the reproduction temperature range, that is, a leakage magnetic field control layer described later may be provided.

According to a second aspect of the present invention, there is provided a magneto-optical recording medium having a recording layer on which information is recorded and a magnetic domain expansion reproducing layer, wherein a recording mark is formed on the magneto-optical recording medium. In this case, the laser power at which a recording mark disappears when a laser beam is irradiated on the magneto-optical recording medium with various laser powers is denoted by P1, and when no recording mark is formed on the magneto-optical recording medium, When a laser signal is irradiated at various laser powers while applying an alternating magnetic field to the recording medium and a reproduction signal from the magnetic domain expansion reproduction layer is detected, and the reproduction signal amplitude becomes almost zero, the laser power is P2. The laser power P1
And P2 satisfy the relationship of P2 <P1. In such a magneto-optical recording medium, since the Curie temperature of the magnetic domain expansion reproducing layer is lower than the Curie temperature of the recording layer, minute recording magnetic domains are formed in the recording layer as in the magneto-optical recording medium of the first embodiment. be able to.

According to a third aspect of the present invention, in a magneto-optical recording medium having a recording layer on which information is recorded and a magnetic domain expansion reproducing layer, the recording layer has a thickness of 10 nm to 100 nm.
m, and the magnetic domain expansion reproduction layer has a temperature of from room temperature to 200 ° C.
A magneto-optical recording medium having a compensation temperature in the range of

In the magneto-optical recording medium of the third embodiment, the recording layer has a thickness of 10 nm to 100 nm, so that minute recording marks can be easily formed on the recording layer. To form a recording mark on the recording layer, usually, the recording layer is locally heated to near the Curie temperature by a laser beam, and an external magnetic field in a direction corresponding to the recording information is applied to the heated region. Thereafter, in the cooling process, the magnetization of the heated area is aligned in the direction of the external magnetic field, and a magnetic domain corresponding to the information is formed in the recording layer. In a conventional magneto-optical recording medium, the thickness of the recording layer is as large as about 200 nm, so that even if a micro mark of, for example, about 0.2 μm is recorded, it is difficult to obtain a recording mark of a desired shape. In some cases, the formed minute mark disappeared. The following reasons can be considered as this cause. That is, since the mark length of the minute recording mark is shorter than the film thickness of the recording layer, the effective domain wall energy of the recording mark increases, and the domain wall of the recording mark moves so as to cancel the domain wall energy. I will. Therefore, it is considered that the recording mark cannot be stably present. On the other hand, the magneto-optical recording medium of the present invention
Since the thickness of the recording layer is as thin as 10 nm to 100 nm, the effective domain wall energy of the recording mark is reduced, so that minute recording magnetic domains can be reliably formed in the recording layer.
In order to further reduce the effective domain wall energy of the recording mark and reliably form the recording mark, the thickness of the recording layer is more preferably from 10 nm to 50 nm.

The recording layer has a thickness of 10 nm to 100 n.
When the thickness is reduced to about m, the magnetic field strength of the leakage magnetic field from the recording layer decreases, so that the leakage magnetic field from the recording layer reliably reaches the magnetic domain expansion reproduction layer, the distance between the recording layer and the magnetic domain expansion reproduction layer, that is, It is preferable that the film thickness of the non-magnetic layer and the like interposed therebetween is 1 nm to 20 nm.

In the magneto-optical recording medium of the fourth aspect, in order to further increase the temperature gradient of the coercive force of the magnetic domain enlarging reproducing layer and further enhance the reproducing resolution, the compensation temperature of the magnetic domain enlarging reproducing layer is from room temperature to 200 ° C. And preferably 50 ° C to 150 ° C.
° C. The magneto-optical recording medium of the fourth aspect may include the above-described auxiliary magnetic layer (leakage magnetic field suppressing layer). The auxiliary magnetic layer is
It can be composed of TbCo or TbFeCo.

According to a fourth aspect of the present invention, there is provided a magneto-optical recording medium, comprising: a recording layer;
When the Curie temperature of the magnetic domain expansion reproducing layer is Tc and the compensation temperature is Tcomp, ΔT = Tc−Tcomp is as follows.
A magneto-optical recording medium that satisfies the relationship of 0 ° C. ≦ ΔT ≦ 300 ° C. is provided.

The magneto-optical recording medium of the fourth embodiment has a magnetic domain enlarging reproducing layer in which the difference between the compensation temperature Tcomp of the magnetic domain enlarging reproducing layer and the Curie temperature Tc is 0 ° C. to 300 ° C.
The coercive force of the magnetic domain expansion reproducing layer in the temperature range between mp and Tc rises sharply from high temperature to low temperature as shown in FIG. A magneto-optical recording medium provided with a magnetic domain expansion reproducing layer having such magnetic characteristics has a higher reproducing resolution than before. The reason will be described below.

FIG. 4A conceptually shows the spatial intensity distribution of the leakage magnetic field of the recording layer and the spatial intensity distribution of the coercive force of the magnetic domain expansion reproducing layer as viewed from a cross section. Since the center of the light spot is high in temperature, the leakage magnetic field Hlw from the recording layer is large, and the temperature decreases from the center of the spot toward the outer periphery. Therefore, the leakage magnetic field Hlw from the recording layer decreases from the center of the spot toward the outer periphery. ing. In the conventional magneto-optical recording medium, since the temperature gradient of the coercive force of the magnetic domain expansion reproducing layer in the temperature region from the compensation temperature to the Curie temperature was gentle, as shown in FIG. The coercive force Hc ′ also gradually changes at the position in the X direction about the center of the light spot. For this reason, there is a possibility that the adjacent recording magnetic domain 42 may be transferred to the magnetic domain enlarged reproduction layer under the influence of the leakage magnetic field 43 of the recording magnetic domain 42 adjacent to the recording magnetic domain 41 to be reproduced. In particular, FIG.
As shown in (B), when reproducing the magnetic domain 45 in the erasing direction, the leakage magnetic field 47 from the recording magnetic domain 46 adjacent thereto is reproduced.
Exceeds the coercive force Hc ′ of the magnetic domain expansion reproduction layer,
There is a possibility that the recording magnetic domain 46 is erroneously transferred to the magnetic domain enlarged reproduction layer and the information is reproduced. On the other hand, in the present invention, the coercive force Hc of the magnetic domain expansion reproducing layer sharply rises in a temperature region from the Curie temperature to the compensation temperature,
As shown in FIG. 4A, the coercive force H of the magnetic domain expansion reproduction layer
c greatly changes in a narrow range from the center of the light spot toward the X direction. As a result, only the desired recording magnetic domains can be transferred to the magnetic domain enlarged reproduction layer. FIG.
When reproducing the magnetic domain 45 in the erasing direction as shown in (B), the coercive force Hc of the magnetic domain enlarged reproduction layer is larger than the leakage magnetic field 47 from the recording magnetic domain 46 adjacent to the magnetic domain 45 in the erasing direction. The adjacent recording magnetic domain 46 is prevented from being erroneously reproduced.

In the magneto-optical recording medium of the fourth embodiment, the compensation temperature of the magnetic domain expansion reproducing layer is set to room temperature (about 20 ° C.) in order to further increase the reproducing resolution by making the temperature gradient of the coercive force of the magnetic domain expansion reproducing layer steeper. ) To 200 ° C., and within this temperature range, a bit error rate of 1.0 × 10 ⁻⁴ or less can be secured. The compensation temperature of the magnetic domain expansion reproducing layer is preferably 40 to 190 ° C, more preferably 50 ° C.
１５０150 ° C. Particularly, in order to secure a bit error rate of 1.0 × 10 ⁻⁵ or less, 70 ° C. to 140 ° C. is preferable.

According to a fifth aspect of the present invention, there is provided a magneto-optical recording medium, comprising: a recording layer; a magnetic domain expansion layer; and an auxiliary magnetic layer having a Curie temperature higher than the Curie temperature of the recording layer. A magneto-optical recording medium is provided in which the auxiliary magnetic layer has a magnetic characteristic in which the saturation magnetization decreases as the temperature rises in the reproduction temperature range.

Since the magneto-optical recording medium of the fifth aspect has an auxiliary magnetic layer (leakage magnetic field control layer), it is possible to suppress large fluctuations in the leakage magnetic field from the recording layer due to fluctuations in the read power (reproduction light power). Can be. The reason why the read power margin can be expanded by adding the auxiliary magnetic layer will be described below with reference to the drawings. FIG. 9 conceptually shows the spatial distribution of the leakage magnetic field of the recording layer 5 and the spatial distribution of the coercive force of the magnetic domain expansion reproducing layer (not shown) in the cross-sectional direction of the magneto-optical recording medium having no auxiliary magnetic layer. The temperature distribution of the magneto-optical recording medium heated by the light spot follows a Gaussian distribution, with the highest temperature near the center of the spot, and the temperature gradually decreases from the center of the spot toward the outside. According to this temperature distribution, the leakage magnetic field Hlw from the recording layer 5 is large at the spot center position in the X direction and gradually decreases toward the outside. On the other hand, the coercive force Hc of the magnetic domain expansion reproducing layer increases from the center of the light spot toward the outside in the X direction according to the temperature distribution. In this state, the recording mark 51
Only in the X direction position, the leakage magnetic field Hlw from the recording mark 51 exceeds the coercive force Hc of the magnetic domain expansion reproduction layer. Therefore, only the magnetization of the recording mark 51 is transferred to the magnetic domain enlarging and reproducing layer, expanded and reproduced.

In FIG. 9, when the reproducing light power increases, the temperature in the light spot rises, so that the leakage magnetic field from the recording layer usually increases from Hlw to Hlw ', whereas the magnetic domain expansion increases. The coercive force of the reproducing layer changes from Hc to H
c ′. In this state, the leakage magnetic field Hlw 'of the recording layer exceeds the coercive force Hc of the magnetic domain expansion reproduction layer not only in the X direction position of the recording mark 51 but also in the X direction positions of the recording marks 52 and 53. As a result, the recording mark 5
Not only 1 but also the recording marks 52 and 53 may be transferred to the magnetic domain enlarged reproduction layer and reproduced. That is, in the conventional magnetic domain expansion type magneto-optical recording medium, since the leakage magnetic field of the recording layer greatly changes due to a change in the reproducing light power,
Depending on the reproducing light power, it was difficult to reliably reproduce a desired recording mark on the recording layer, and the reproducing light power margin was narrow.

FIG. 10 shows the spatial distribution of the leakage magnetic field from the recording layer 5 and the auxiliary magnetic layer 7 in the sectional direction of the magneto-optical recording medium provided with the auxiliary magnetic layer 7 according to the present invention, and the space of the coercive force of the magnetic domain expansion reproducing layer. The distribution is shown conceptually. Auxiliary magnetic layer 7
Has a Curie temperature higher than the Curie temperature of the recording layer, and is not recorded by a recording magnetic field, for example, in a recording temperature range of 0 ° C. to 300 ° C. That is, since the coercive force of the auxiliary magnetic layer is higher than the recording magnetic field in this temperature range, it is possible to always have magnetization in the initialization direction (downward in the figure) as shown in FIG. Therefore, the auxiliary magnetic layer 7 has the recording marks 54, 55,
A leakage magnetic field having a direction opposite to that of the magnetization 56 is generated. Also,
As shown in FIG. 11, the auxiliary magnetic layer 7 has a saturation magnetization (Ms) in the reproduction temperature range (for example, 150 ° C. to 200 ° C.).
(° C.). Therefore, the leakage magnetic field from the auxiliary magnetic layer 7 decreases as the coercive force of the magnetic domain expansion reproducing layer in FIG. 10 changes from Hc to Hc ′ as the reproducing light power increases. As shown in FIG. 11, the temperature rise (Δ
When the increase ΔMs (RE) of the leakage magnetic field of the recording layer due to T) becomes substantially equal to the decrease ΔMs (LC) of the leakage magnetic field from the auxiliary magnetic layer 7, they cancel each other out, and the leakage magnetic field increases as the power of the reproduction light increases. There is no change. The change in the leakage magnetic field from the auxiliary magnetic layer 7 can cancel the increase in the leakage magnetic field of the recording layer due to the increase in the power of the reproduction light. Therefore, as shown in FIG. 10, even if the reproducing light power is increased, the coercive force of the magnetic domain expansion reproducing layer is changed from Hc to Hc.
The recording layer 5 (and the auxiliary magnetic layer 7) is reduced to c ′
Magnetic field Hlw "from the recording mark 54 hardly changes, and as a result, the leakage magnetic field Hlw
w "exceeds the coercive force Hc of the magnetic domain enlarging and reproducing layer. Therefore, regardless of the reproducing light power, only the desired recording mark can be reproduced through the magnetic domain enlarging and reproducing layer.

As the auxiliary magnetic layer, TbCo, TbFe
Rare earths such as Co, DyFeCo, TbGdFeCo
It can be composed of a transition metal material. As described above, a rare earth-rich rare earth-transition metal material can be used as a material whose saturation magnetization decreases as the temperature rises in the reproduction temperature range. The Curie temperature of the auxiliary magnetic layer is
It is preferable that the temperature is adjusted to be higher than the Curie temperature of the recording layer but higher by 50 ° C. than the Curie temperature of the recording layer.
Further, the compensation temperature of the auxiliary magnetic layer is set at 250 to provide a sufficiently high coercive force when information is recorded on the recording layer.
It is preferable that the temperature is not lower than ° C. Note that the auxiliary magnetic layer is made of Tb
The relationship between the Tb concentration, the compensation temperature, and the Curie temperature when composed of Co is as shown in FIG. 15, and when the auxiliary magnetic layer is composed of TbFeCo, Tb and Fe
It is known that the relationship among the concentration, the compensation temperature, and the Curie temperature shows the relationship shown in FIG. 16 (FIGS. 15 and 1).
All of the graphs in Fig. 6 are excerpts from Toshio Niihara and a doctoral dissertation at Nagoya University, "Research on the Development of Magneto-Optical Disk Media" (July 23, 1992).

When the auxiliary magnetic layer is provided, it is desirable to reduce the thickness of the recording layer in order to effectively cancel the leakage magnetic field of the recording layer.
Desirably, it is set to 00 nm. The auxiliary magnetic layer can be provided, for example, above or below the recording layer via a nonmagnetic layer so as not to exchange-couple with the recording layer.

In the magneto-optical recording medium according to the first to fifth aspects of the present invention, the magnetic material forming the recording layer is, for example, T
bFeCo, TbFe, GdFe, GdFeCo, Tb
A rare earth-transition metal alloy such as Co, DyFeCo, DyFe, and DyCo, or a material obtained by adding Cr, Zr, or the like to these alloys can be used. The material constituting the magnetic domain expansion reproduction layer is, for example, GdFeCo, G
dFe, GdTbFeCo, GdDyFeCo, GdD
A rare earth-transition metal alloy such as yTbFeCo, an alternate stack of a Pt layer and a Co layer, a PtCo alloy, or the like can be used. To adjust the Curie temperature of the magnetic material constituting these recording layer and magnetic domain expansion reproducing layer, for example, when forming them by sputtering,
The composition of the magnetic material may be adjusted. By using such a method, it is possible to adjust the Curie temperature of the magnetic domain expansion reproducing layer to be lower than the Curie temperature of the recording layer.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the magneto-optical recording medium according to the present invention will be specifically described, but the present invention is not limited thereto.

[0032]

Embodiment 1 FIG. 2 shows a sectional structure of a magneto-optical recording medium according to the present invention. The magneto-optical recording medium 100 has a structure in which a dielectric layer 2, a magnetic domain expansion reproducing layer 3, a nonmagnetic layer 4, a recording layer 5, and a protective layer 6 are sequentially laminated on a transparent substrate 1.

In the structure shown in FIG.
Is a polycarbonate substrate produced by using an injection molding machine (not shown), and has irregularities corresponding to the preformat pattern on its surface and a thickness of 1.2 mm. The dielectric layer 2 is a layer for causing a reproduction light beam to cause multiple interference in the layer to substantially increase the detected Kerr rotation angle, and is made of SiN. The magnetic domain expansion reproduction layer 3
The magnetic domain transferred from the recording layer 6 can be reproduced by enlarging the magnetic domain. The perpendicular magnetization film GdFe showing ferrimagnetism is provided.
It is configured using Co. The non-magnetic layer 4 is a layer for cutting the exchange coupling force between the reproducing layer 3 and the recording layer 5 to perform magnetostatic coupling, and is made of SiN. The recording layer 5 is a layer in which information is recorded as magnetization information, and is configured using a rare earth-transition metal amorphous film TbFeCo having perpendicular magnetization. The protective layer 6 includes the layers 2 to 5 laminated on the substrate 1.
And is made of SiN. These layers 2 to 6 were sequentially formed under the following conditions using a sputtering device (not shown).

[0034] In the deposition of the dielectric layer 2, using Si as a target material was subjected to sputtering in a mixed atmosphere of Ar and N _2. The thickness of the dielectric layer 2 was set to 20 nm. In the formation of the magnetic domain expansion reproducing layer 3, a single target of Gd, Fe and Co was simultaneously sputtered. In the simultaneous sputtering, the film composition was adjusted by controlling the ratio of the power supplied to each target. Further, the film composition of the magnetic domain expansion reproducing layer 3 was adjusted so that the compensation temperature and the Curie temperature were about 80 ° C. and about 270 ° C., respectively. The film thickness was 20 nm.

[0035] In the formation of the non-magnetic layer 4, using Si as a target material was subjected to sputtering in an Ar + _{N 2} atmosphere. The film thickness was 20 nm. In forming the recording layer 5, Tb, Fe and Co simple targets were simultaneously sputtered, and the film composition of the recording layer was adjusted so that the compensation temperature was about 25 ° C. and the Curie temperature was 310 ° C. The thickness of the recording layer 5 was 200 nm. The formation of the protective layer 6, using Si as a target material was subjected to sputtering in an Ar + N ₂ atmosphere. The film thickness was 20 nm. Thus, the magneto-optical recording medium 100 having the laminated structure shown in FIG. 2 was manufactured.

Next, in the magneto-optical recording medium 100,
Information was recorded using a recording / reproducing device (not shown) by the optical pulse magnetic field modulation method as described below. While rotating the magneto-optical recording medium at a linear velocity of 1.875 m / sec, a laser beam was irradiated and a recording magnetic field was applied so that a mark pattern in which recording marks were continuous at regular intervals was formed. The recording magnetic field intensity was 200 (Oe), and the recording power was 12 mW and 11 m
Irradiation was performed at two different powers of W. Observation of recording marks on the magneto-optical recording medium after recording was performed using a scanning magnetic force microscope (MFM). As a result, an ultra-fine recording magnetic domain having a length in the track direction of 0.15 μm was formed on the recording layer. Confirmed that. FIG. 6 shows a recording mark pattern obtained by a scanning magnetic force microscope as a reference diagram. In FIG. 6, the upper recording mark pattern is when the laser light power (recording power) is 12 mW, and the lower recording mark pattern is when the laser light power is 1 mW.
This is the case of 1 mW. From this reference diagram, it can be seen that the contour and shape of the minute recording magnetic domain are clear.

[0037]

Example 2 A magneto-optical recording medium was manufactured in the same manner as in Example 1 except that the thickness of the recording layer was changed to 50 nm.
Information was recorded on the obtained magneto-optical recording medium using the same recording / reproducing apparatus as in Example 1 by an optical pulse magnetic field modulation method. During recording, the magneto-optical recording medium was moved at a linear velocity of 1.250 m.
While rotating at / sec, a recording laser beam was applied and a recording magnetic field was applied in the same manner as in Example 1 so that a mark pattern in which recording marks continued at a constant interval was formed. The recording mark recorded on the recording layer in this way is
Observation was performed using a scanning magnetic force microscope. FIG. 7 is a reference diagram showing a state of a recording mark pattern obtained by a scanning magnetic force microscope. In FIG. 7, the upper recording mark pattern is when the laser light power is 12 mW,
The lower recording mark pattern has a laser beam power of 11 m.
This is the case for W. As can be seen from the reference diagram of FIG. 7, the recording layer has an ultrafine recording magnetic domain having a length of 0.10 μm in the track direction, and the contour and shape of the ultrafine recording magnetic domain are all clear. Was.

[0038]

Comparative Example The compensation temperature of the magnetic domain expansion reproducing layer was changed to 25 ° C., the Curie temperature was changed to 300 ° C., and the compensation temperature of the recording layer was changed to 35 ° C.
A magneto-optical recording medium was produced in the same manner as in Example 1 except that the temperature and the Curie temperature were changed to 270 ° C. Information was recorded on the obtained magneto-optical recording medium using the same recording / reproducing apparatus as in Example 1 by an optical pulse magnetic field modulation method. At the time of recording, the power of the recording laser beam was 12 mW, and the intensity of the recording magnetic field was 200 (Oe). The recording is performed by rotating the magneto-optical recording medium at two linear velocities of 2.5 m / sec and 1.250 m /. The recording was performed such that a continuous mark pattern and a mark pattern in which recording marks having a mark length of 0.1 μm continued at a constant interval were formed. The continuous marks thus recorded on the recording layer were observed using a scanning magnetic force microscope. FIG. 8 shows a state of a recording mark pattern obtained by a scanning magnetic force microscope as a reference diagram. In FIG. 8, the upper recording mark pattern has a mark length of 0.2 μm.
m, and the lower recording mark pattern has a mark length of 0.1 μm. As can be seen from this reference drawing, the outline of any recording mark formed on the recording layer was extremely unclear. In particular, in the magneto-optical recording medium of this example, a recording mark pattern composed of recording marks having a mark length of 0.1 μm could not be formed on the recording layer.

[0039]

Example 3 In Example 1, a plurality of magneto-optical recording medium samples were manufactured by changing the compensation temperature to various values by changing the composition of the magnetic expansion reproducing layer, and the conditions of Example 1 were applied to each sample. To form a recording mark. Then
These samples were reproduced to observe the bit error rate. The reproduction condition is as follows: the reproduction light power is 2.10 mW
W, the reproducing magnetic field is ± 200 (Oe) (about ± 15800 A /
m). FIG. 14 shows the relationship between the compensation temperature and the bit error rate for each sample. As can be seen from FIG. 14, when the compensation temperature of the magnetic domain expansion reproduction layer is lower than 20 ° C. (room temperature), the bit error rate exceeds 1 × 10 ⁻⁴ and the reproduction resolution is reduced. This is because the temperature gradient of the coercive force of the magnetic domain expansion reproducing layer becomes gentle because the compensation temperature of the magnetic domain expansion reproducing layer is lower than 20 ° C., and the magnetic domain in contact with the recording magnetic domain (mark) of the recording layer to be reproduced is erroneously determined. It is considered that this is due to transfer to the magnetic domain expansion reproduction layer.
When the compensation temperature of the magnetic domain expansion reproduction layer exceeds 200 ° C., the bit error rate exceeds 1 × 10 ⁻⁴ , and the reproduction resolution decreases. This is presumably because the compensation temperature is close to the reproduction temperature, so that the coercive force of the magnetic domain expansion reproduction layer increases, and transfer from the recording layer to the magnetic domain expansion reproduction layer and expansion of the transfer magnetic domain cannot be performed. Therefore, according to the results of FIG. 14, the compensation temperature of the magnetic domain expansion reproducing layer is about 20 ° C. (room temperature) to 2
00 ° C is preferred, more preferably 40 to 190 ° C, and even more preferably 50 to 150 ° C. In particular, it is understood that 70 ° C. to 140 ° C. is preferable in order to secure a bit error rate of 1.0 × 10 ⁻⁵ or less.

[0040]

Fourth Embodiment FIG. 12 shows a sectional structure of a magneto-optical recording medium according to another embodiment of the present invention. Magneto-optical recording medium 200
Are a dielectric layer 2, a magnetic domain expansion reproducing layer 3, a nonmagnetic layer 4, a recording layer 5, a nonmagnetic layer 12, a leakage magnetic field control layer 1 on a transparent substrate 1.
4, a structure in which the protective layer 6 and the heat radiation layer 16 are sequentially laminated.

In the structure shown in FIG.
Is a polycarbonate substrate produced by using an injection molding machine (not shown), and has irregularities corresponding to the preformat pattern on its surface and a thickness of 1.2 mm. The dielectric layer 2 is a layer for causing a reproduction light beam to cause multiple interference in the layer to substantially increase the detected Kerr rotation angle, and is made of SiN. The magnetic domain expansion reproduction layer 3
The magnetic domain transferred from the recording layer 6 can be reproduced by enlarging the magnetic domain. The perpendicular magnetization film GdFe showing ferrimagnetism is provided.
It is configured using Co. The non-magnetic layer 4 is a layer for cutting the exchange coupling force between the reproducing layer 3 and the recording layer 5 to perform magnetostatic coupling, and is made of SiN. The recording layer 5 is a layer in which information is recorded as magnetization information, and is configured using a rare earth-transition metal amorphous film TbFeCo having perpendicular magnetization. The nonmagnetic layer 6 is a layer for cutting the exchange coupling force between the recording layer 5 and the stray magnetic field control layer 7 to perform magnetostatic coupling.
It is configured using SiN. The leakage magnetic field control layer 7 is a layer that controls the leakage magnetic field from the recording layer 5 to the magnetic domain expansion reproduction layer 3, and is configured using a perpendicular magnetization film TbCo. The protective layer 6 is a layer for protecting each layer laminated on the substrate 1 and is made of SiN. The heat radiation layer 16 is a layer for efficiently releasing heat from the magneto-optical recording medium during recording.
It is made of AlTi. These layers were sequentially formed under the following conditions using a sputtering apparatus (not shown).

[0042] In the deposition of the dielectric layer 2, using Si as a target material, subjected to sputtering in an Ar + _{N 2} atmosphere, was 60nm thickness. In the formation of the magnetic domain expansion reproducing layer 3, a single target of Gd, Fe and Co was simultaneously sputtered. In the simultaneous sputtering, the film composition was adjusted by controlling the ratio of the power supplied to each target. Also,
The compensation temperature and Curie temperature are about 80 ° C and about 27, respectively.
The film composition of the magnetic domain expansion reproducing layer 3 was adjusted to be 0 ° C. The film thickness was 20 nm.

In forming the non-magnetic layer 4, sputtering was performed in an Ar + N ₂ atmosphere using Si as a target material, and the film thickness was set to 5 nm. In forming the recording layer 5, T
b, Fe and Co simple targets were simultaneously sputtered, and the film composition of the recording layer was adjusted so that the compensation temperature was about 25 ° C. and the Curie temperature was 310 ° C. The thickness of the recording layer 5 is 500
nm. In the formation of the leakage magnetic field control layer 7, Tb and C
o Simultaneous sputtering of a single target, compensation temperature of about 31
The film composition was adjusted so that the temperature was 0 ° C. and the Curie temperature was 350 ° C. The film thickness of the leakage magnetic field control layer 14 was 50 nm.
The formation of the protective layer 8, using Si as a target material was subjected to sputtering in an Ar + N ₂ atmosphere. The film thickness was 20 nm. The formation of the heat dissipation layer 16, using an AlTi as a target material, subjected to sputtering in an Ar + _{N 2} atmosphere, AlTi layer with a film thickness of 30nm was obtained. Thus, the magneto-optical recording medium 2 having the laminated structure shown in FIG.
00 was produced.

Information was recorded on the obtained magneto-optical recording medium 200 by using the recording / reproducing apparatus used in the first embodiment by the optical pulse magnetic field modulation method under the same recording conditions as in the second embodiment. A recorded mark is reproduced with various reproducing light powers, and a bit error rate (BE) with respect to the reproducing light power is reproduced.
R) was measured. In the measurement of the bit error rate, the allowable limit (upper limit) of the measured value was set to 10 ^-4 . FIG. 13 shows the measurement results. The minimum value of the reproduction power is about 1.90 mW and the maximum value is about 2.30 m within the allowable limit of the measured value.
W, from which the reproduction power margin P1 is equal to 0.
It was found to be 4 mW.

For reference, recording and reproduction were performed on the magneto-optical recording medium manufactured in Example 2 in the same manner as in this example. The minimum value of the reproduction power exceeding the allowable limit (10 ⁻⁴ ) is about 2.
00mW, the maximum is about 2.10mW, ie
The reproducing power margin P1 was 0.1 mW, and it was found that a wider power margin was achieved in Example 4.

Although the magneto-optical recording medium of the present invention has been described in detail with reference to the embodiments, the present invention is not limited thereto. For example, in the above Examples 1 and 2, the magneto-optical recording medium for MAMMOS having the laminated structure shown in FIG. 2 was manufactured.
No. 98/02878. Further, although an alternating magnetic field is applied during reproduction of the magneto-optical recording medium, it is also possible to perform reproduction while expanding magnetic domains by a DC magnetic field, no magnetic field, or optical modulation.

[0047]

According to the magneto-optical recording medium of the present invention, by controlling the Curie temperature of the magnetic domain expansion reproducing layer to be lower than the Curie temperature of the recording layer, control is performed so that the saturation magnetization of the magnetic domain expansion reproducing layer does not appear during recording. So, for example, 0.2μ
An extremely small recording mark of m or less can be reliably formed. Also, the formed ultra-small recording mark is a MAMM
Since reproduction can be performed with a sufficient reproduction signal intensity in accordance with the reproduction principle of the OS, it is extremely suitable as a next-generation ultra-high-density recording medium.

Further, the magneto-optical recording medium of the present invention can further increase the reproducing power margin by including the leakage magnetic field control layer having a Curie temperature higher than the Curie temperature of the recording layer. Therefore, if the magneto-optical recording medium of the present invention is used, even if minute magnetic domains are formed for high-density recording, the reproduction power can be controlled without strictly controlling the reproduction power with high precision and with the amplified reproduction signal intensity. The recorded information can be reproduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing the temperature dependence of the magnetization of the recording layer and the magnetic domain expansion reproduction layer of the magneto-optical recording medium of the present invention and the temperature dependence of the coercive force of the magnetic domain expansion reproduction layer.

FIG. 2 is a diagram schematically showing a cross-sectional structure of an example of the magneto-optical recording medium of the present invention.

FIG. 3 is a diagram showing the temperature dependence of the Kerr rotation angle (θk) of the magnetic domain expansion reproduction layer.

FIG. 4 is a view conceptually showing a state when a spatial intensity distribution of a leakage magnetic field from a recording layer and a spatial intensity of a coercive force of a magnetic domain expansion reproducing layer are viewed from a cross section.

FIG. 5 is a diagram showing temperature dependence of magnetization of a recording layer and a magnetic domain expansion reproducing layer of a conventional magneto-optical recording medium.

FIG. 6 is a reference diagram of a recording mark pattern of the magneto-optical recording medium of Example 1 obtained by a scanning magnetic force microscope.

FIG. 7 is a reference diagram of a recording mark pattern of the magneto-optical recording medium of Example 2 obtained by a scanning magnetic force microscope.

FIG. 8 is a reference diagram of a recording mark pattern of a magneto-optical recording medium of a comparative example obtained by a scanning magnetic force microscope.

FIG. 9 is a diagram conceptually showing a spatial distribution of a leakage magnetic field of a recording layer and a spatial distribution of a coercive force of a magnetic domain expansion reproducing layer in a sectional direction of a magneto-optical recording medium having no auxiliary magnetic layer.

FIG. 10 is a diagram conceptually showing a spatial distribution of a leakage magnetic field from a recording layer and an auxiliary magnetic layer and a spatial distribution of a coercive force of a magnetic domain expansion reproducing layer in a cross-sectional direction of a magneto-optical recording medium having an auxiliary magnetic layer. .

FIG. 11 is a graph showing a change in saturation magnetization (Ms) with respect to temperature of the auxiliary magnetic layer and the recording layer.

FIG. 12 is a schematic diagram showing a cross-sectional structure of a magneto-optical recording medium manufactured in Example 4.

FIG. 13 is a graph showing a change in a bit error rate with respect to a reproduction light power of a magneto-optical recording medium manufactured in Examples 2 and 3.

FIG. 14 is a graph showing the relationship between the compensation temperature and the bit error rate for the sample manufactured in Example 3.

FIG. 15 is a graph showing the relationship between the compensation temperature of TbCo and the Tb content.

FIG. 16 is a graph showing the relationship between the compensation temperature and the composition of TbFeCo.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Dielectric layer 3 Magnetic domain expansion reproduction layer 4, 12 Nonmagnetic layer 5 Recording layer 6 Protective layer 14 Leakage magnetic field control layer 16 Heat dissipation layer 100, 200 Magneto-optical recording medium

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G11B 11/105 553 G11B 11/105 553H (72) Inventor Hiroyuki Awano 1-88 Ushitora, Ishigaki, Ibaraki-shi, Osaka No. Hitachi Maxell, Inc. F-term (reference) 5D075 CD11 EE03 FF12

Claims (15)

[Claims] 1. A magneto-optical recording medium, comprising: a recording layer on which information is recorded; a magnetic domain enlarging and reproducing layer on which magnetic domains are transferred from the recording layer and the transferred magnetic domains are enlarged;
A magneto-optical recording medium, wherein the Curie temperature of the magnetic domain expansion reproduction layer is lower than the Curie temperature of the recording layer, and the magnetic domain expansion reproduction layer has a compensation temperature in a range from room temperature to 200 ° C. 2. The recording layer according to claim 1, wherein the recording layer has a thickness of 10 nm to 100 nm.
2. The magneto-optical recording medium according to claim 1, wherein the value is in the range of nm. 3. The Curie temperature of the magnetic domain expansion reproducing layer is set to T.
c, when the compensation temperature is Tcomp, their difference Δ
3. The magneto-optical recording medium according to claim 1, wherein T (= Tc-Tcomp) satisfies a relationship of 0 ° C. ≦ ΔT ≦ 300 ° C. 4. An auxiliary magnetic layer according to claim 1, further comprising an auxiliary magnetic layer having a Curie temperature higher than the Curie temperature of the recording layer and having a magnetic characteristic in which a saturation magnetization decreases with a rise in temperature in a reproduction temperature range. A magneto-optical recording medium according to claim 1. 5. A rare earth element in which the auxiliary magnetic layer is RE-rich.
5. The magneto-optical recording medium according to claim 4, comprising a transition metal material. 6. When a recording mark is formed on the magneto-optical recording medium, a laser power at which the recording mark disappears when the magneto-optical recording medium is irradiated with laser light at various laser powers is P1, When a recording signal is not formed on the magneto-optical recording medium, a laser beam is irradiated with various laser powers while applying an alternating magnetic field to the magneto-optical recording medium, and a reproduction signal from the magnetic domain expansion reproduction layer is detected. The magneto-optical device according to any one of claims 1 to 4, wherein the laser powers P1 and P2 satisfy a relationship of P2 <P1, where P2 is the laser power at which the amplitude of the reproduced signal becomes substantially zero. recoding media. 7. A magneto-optical recording medium having a recording layer on which information is recorded and a magnetic domain enlarging / reproducing layer, wherein a recording mark is formed on the magneto-optical recording medium. The laser power at which a recording mark disappears when a laser beam is irradiated with the laser power of P is defined as P1, and when no recording mark is formed on the magneto-optical recording medium, an alternating magnetic field is applied to the magneto-optical recording medium. When the laser power at which the reproduced signal amplitude becomes almost zero when the reproduced signal from the magnetic domain expansion reproducing layer is detected by irradiating the laser beam with various laser powers is P2, the laser powers P1 and P2 are A magneto-optical recording medium satisfying a relationship of P2 <P1. 8. The auxiliary magnetic layer according to claim 7, further comprising a magnetic layer having a Curie temperature higher than the Curie temperature of the recording layer and having a magnetic characteristic in which the saturation magnetization decreases with a rise in temperature in a reproduction temperature range. Magneto-optical recording medium. 9. A magneto-optical recording medium having a recording layer on which information is recorded and a magnetic domain enlarging and reproducing layer, wherein the thickness of the recording layer is in the range of 10 nm to 100 nm, A magneto-optical recording medium having a compensation temperature in the range of 200 ° C. 10. The auxiliary magnetic layer according to claim 9, further comprising an auxiliary magnetic layer having a Curie temperature higher than the Curie temperature of the recording layer and having a magnetic characteristic in which a saturation magnetization decreases with a rise in temperature in a reproduction temperature range. Magneto-optical recording medium. 11. The magneto-optical recording medium according to claim 10, wherein the auxiliary magnetic layer is made of a RE-rich rare earth-transition metal material. 12. A magneto-optical recording medium, comprising: a recording layer; and a magnetic domain expansion reproduction layer, wherein when the Curie temperature of the magnetic domain expansion reproduction layer is Tc and the compensation temperature is Tcomp, ΔT = Tc− Tcomp is 0 ° C ≦ ΔT ≦ 3
A magneto-optical recording medium that satisfies the relationship of 00 ° C. 13. The magneto-optical recording medium according to claim 12, wherein the compensation temperature is in a range from room temperature to 200 ° C. 14. A magneto-optical recording medium, comprising: a recording layer; a magnetic domain expansion layer; and an auxiliary magnetic layer having a Curie temperature higher than the Curie temperature of the recording layer, wherein the auxiliary magnetic layer is in a reproduction temperature range. A magneto-optical recording medium having magnetic characteristics in which the saturation magnetization decreases as the temperature rises. 15. The magneto-optical recording medium according to claim 14, wherein the auxiliary magnetic layer is made of an RE-rich rare earth-transition metal material.