JP2007102829A - Magneto-optical recording medium and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magneto-optical recording medium capable of obtaining excellent recording/reproducing characteristics even when the magneto-optical recording medium is irradiated with a blue laser beam spot of ≤450 nm wavelength by setting the track pitch of recording tracks formed on the substrate of the magneto-optical recording medium half as large as the track pitch of a Blu-ray Disc in the magneto-optical recording medium in which at least three or more magnetic layers for enlarging and reading a magnetic domain by magnetic wall movement are laminated and to provide a method for manufacturing the magneto-optical recording medium. <P>SOLUTION: In the magneto-optical recording medium 10 constituted by laminating at least three or more magnetic layers 16, 14, 13 for enlarging and reading a magnetic domain by magnetic wall movement on a substrate 11 on which projected lands 11a corresponding to respective recording tracks T for recording/reproducing an information signal are projected to the incident side of a laser beam spot and spirally or concentrically formed in a prescribed track pitch P and recessed grooves 11b are formed on both the sides of each land 11a, in-plane magnetic anisotropy layers 15, 15 having in-plane magnetic anisotropy only on both the sides of a recording track T are formed between a first magnetic layer 16 formed on the incident side of a laser beam spot and a second magnetic layer 14 formed on the lower layer of the first magnetic layer 16. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a magneto-optical recording medium capable of recording and reproducing information signals at an ultra-high density while causing domain wall movement by irradiating a laser beam having a wavelength of 450 nm or less, and a method of manufacturing the magneto-optical recording medium It is.

  In the magneto-optical recording system, the temperature of the ferrimagnetic thin film is locally raised to the Curie point or the vicinity of the compensation point, the coercive force of this portion is reduced, and the externally applied recording magnetic field is applied to the information signal to be recorded. The basic principle is to reverse the direction of magnetization in the direction. In magneto-optical recording / reproducing, in which the magnetization reversed portion, that is, the information bit forms a magnetic domain and reads it out by the magnetic Kerr effect, in order to improve the recording density, the recording bit length (record mark length) is shortened, that is, the information signal When recording marks corresponding to the above are recorded in the form of magnetic domains, it is necessary to reduce the magnetic domains.

  At this time, at least the first to third magnetic layers are sequentially stacked by exchange coupling at room temperature, and the first magnetic layer is formed of a magnetic film having a relatively small domain wall coercive force compared to the third magnetic layer, The two magnetic layer uses a magneto-optical recording medium comprising a magnetic film having a Curie temperature lower than that of the first magnetic layer and the third magnetic layer, and magneto-optical recording using a red laser beam having a wavelength of about 680 nm while applying a reproducing magnetic field. There is a domain wall motion detection type reproduction method in which a good high density recording signal can be obtained by heating the medium (for example, see Patent Document 1).

On the other hand, in the magneto-optical recording method, the reproduction resolution of the magnetic domain (record mark) is almost determined by the wavelength λ of the laser light source of the reproduction optical system and the numerical aperture NA of the objective lens, and the spatial frequency 2NA / λ becomes the reproduction limit. Therefore, in order to increase the recording density on the magneto-optical recording medium, it is conceivable to shorten the wavelength λ of the laser light source or to reduce the spot diameter of the laser beam on the reproducing apparatus side using a high NA objective lens. At this time, since a blue semiconductor laser that emits a blue laser beam having a wavelength of 450 nm or less has been recently developed, information is obtained using the blue semiconductor laser and an objective lens having a numerical aperture NA of 0.7 or more. A magneto-optical recording medium capable of recording and reproducing signals with ultra-high density has been developed (see, for example, Patent Document 2).
Japanese Patent Laid-Open No. 11-86372 JP 2003-511143 A

FIG. 7 is a diagram schematically showing a signal reproducing method for a magneto-optical recording medium having first to third magnetic layers in Conventional Example 1, (a) showing the magneto-optical recording medium, (B) shows the medium temperature distribution, (c) is a diagram showing the force that causes the domain wall motion,
FIG. 8 is a diagram schematically showing a front process on the front side in the moving direction of a laser beam spot when a reproducing magnetic field is applied to the magneto-optical recording medium in Conventional Example 1.
FIG. 9 is a diagram schematically showing the rear process on the rear side in the moving direction of the laser beam spot when a reproducing magnetic field is applied to the magneto-optical recording medium in Conventional Example 1.

  First, the conventional example 1 shown in FIG. 7 to FIG. 9 is a technical idea by the signal reproducing method of the magneto-optical recording medium (magnetic recording medium) disclosed in the above-mentioned Patent Document 1 (Japanese Patent Laid-Open No. 11-86372). This is described with reference to Patent Document 1.

  As shown in FIG. 7A, in the magneto-optical recording medium 100 of Conventional Example 1, the first magnetic layer 101, the second magnetic layer 102, and the third magnetic layer 103 are exchange-coupled at room temperature and sequentially stacked. The first magnetic layer 101 provided on the side irradiated with the laser beam having a wavelength of about 680 nm and serving as the domain wall moving layer has a relative domain wall coercive force as compared with the third magnetic layer 103 serving as the recording layer. The second magnetic layer 102 made of a small magnetic film and serving as an exchange coupling force control layer is made of a magnetic film having a lower Curie temperature than the first magnetic layer 101 and the third magnetic layer 103.

  More specifically, the above-described first to third magnetic layers 101 to 103 include one kind or two kinds of rare earth metal elements such as Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Er. The above is composed of a rare earth-iron group amorphous alloy composed of 10 to 40 atom% and one or more of iron group elements such as Fe, Co, and Ni, 90 to 60 atom%. . Further, it is described that a small amount of elements such as Cr, Mn, Cu, Ti, Al, Si, Pt, and In may be added to these alloys in order to improve corrosion resistance.

  In the magneto-optical recording medium 100 of Conventional Example 1 configured as described above, an external magnetic field from a magnetic head (not shown) is irradiated while recording a red laser beam having a wavelength of about 680 nm from the first magnetic layer 101 side during recording. By recording a recording mark corresponding to the information signal in the third magnetic layer 103, the recording is saved as a magnetization reversal region (hereinafter referred to as a magnetic domain) in the direction of the arrow. The magnetic domains recorded in the three magnetic layers 103 are exchange coupled to the first magnetic layer 101 via the second magnetic layer 102. At this time, the vertical arrows in the first to third magnetic layers 101 to 103 indicate the directions of atomic spins corresponding to “0” and “1” of the recording mark corresponding to the information signal. A domain wall 110 is formed at the boundary between regions where spin directions are opposite to each other.

  Here, when reproducing the magneto-optical recording medium 100 of the conventional example 1, the magneto-optical recording medium 100 is rotated via a spindle motor (not shown), and the magneto-optical recording is performed in the medium moving direction indicated by the arrow. The medium 100 is moved, and on the other hand, a red laser beam having a wavelength of about 680 nm is irradiated onto the magneto-optical recording medium 100 in a spot shape. If the magneto-optical recording medium 100 side is fixed, the laser beam The spot is equivalent to moving in the direction shown by the two-dot chain line.

  During reproduction, when a red laser beam having a wavelength of about 680 nm is irradiated in a spot shape from the first magnetic layer 101 side, the movement of the laser beam spot on the magneto-optical recording medium 100 as shown in FIG. 7B. The temperature gradient characteristic on the front side in the direction has a steeper slope distribution than the temperature gradient characteristic on the rear side in the moving direction of the laser beam spot, and the medium temperature is between the illustrated position x1 and the position x2 with respect to the laser beam spot. The temperature reaches or exceeds the Curie temperature Ts of the second magnetic layer 102. Accordingly, in the region between the position x1 and the position x2, since the second magnetic layer 102 is heated to the Curie temperature Ts or higher, the magnetization of the second magnetic layer 102 disappears, and the first magnetic layer The exchange coupling between the first magnetic layer 103 and the third magnetic layer 103 is cut, and this region is referred to as a bond cutting region S.

  When the domain wall 110 existing in the first magnetic layer 101 enters the section corresponding to the coupling cut region S, the domain wall 110 moves toward the temperature peak as indicated by an arrow A in the first magnetic layer 101. As a result of the movement, a domain wall motion 111A is generated, and the magnetic domain exchange-coupled in the first magnetic layer 101 along with this domain wall motion 111A is enlarged and read as a reproduction mark by a reproduction laser beam spot.

  On the other hand, since the third magnetic layer 103 serving as the recording layer has a sufficiently large coercive force (domain wall coercive force), the domain wall in the third magnetic layer 103 remains in the recorded state without moving. Thereby, the recording density can be remarkably improved by enlarging a minute magnetic domain that cannot be reproduced with normal reproduction resolution.

At this time, when the operation that the domain wall motion 111A is generated by the temperature gradient characteristic on the front side in the moving direction of the reproducing laser beam spot is called a front process, the force F (x) that causes the domain wall motion 111A by the front process is as follows. It is represented by the number 1.

  In this case, σ represents the domain wall energy, and x represents the distance in the track direction in which the moving direction of the laser beam spot is positive.

On the other hand, in the case of a specific recording mark length, the domain wall motion 111B as shown by the arrow B also occurs due to the temperature gradient characteristic on the rear side in the moving direction of the laser beam spot for reproduction, and this is called the rear process. The force F (x) causing the domain wall motion 111B by the process is expressed by the following formula 2.

  Further, the recording mark length at which both the front process and the rear process described above can occur is considered to be 0.25 μm or more when a laser beam spot of about 680 nm is used, but the reproduction signal of a recording mark of 0.25 μm or more is The domain wall motion detection by both processes is detected as a superimposed waveform with a certain delay time. In particular, the superimposed signal detection waveform including the domain wall motion in an unnecessary rear process causes an inconvenient state in normal signal reproduction processing.

  Therefore, according to Patent Document 1 described above, a laser beam is irradiated in a spot shape while applying a reproducing magnetic field on the surface of the magneto-optical recording medium 100 during reproduction, and a temperature region equal to or higher than the Curie temperature Ts of the second magnetic layer 102. The temperature distribution is moved relative to the magneto-optical recording medium 100, and the magnetic wall 110 of the first magnetic layer 101 is heated at the front end in the moving direction of the reproducing laser beam spot. While moving to the high temperature side in the region to cause the domain wall motion 111A, the domain wall 110 of the first magnetic layer 101 is not moved to the high temperature side in the temperature region at the rear end in the moving direction of the laser beam spot for reproduction. Improvement is made so as not to cause the movement 111B.

  That is, by applying a reproducing magnetic field on the surface of the magneto-optical recording medium 100, the domain wall motion 111B in the rear process is suppressed in reproducing a recording mark of any length.

  As described above, since the temperature gradient characteristic of the laser beam spot in the section of the bond cutting region S is (temperature gradient characteristic used in the front process)> (temperature gradient characteristic used in the rear process), this operation is It becomes possible.

  More specifically, in the front process partially enlarged in FIG. 8, the arrow F1 is a domain wall driving force based on the temperature gradient characteristic on the front side in the moving direction of the reproducing laser beam spot, Represented by 1. On the other hand, an arrow F2 in the figure is a domain wall driving force by Zeeman energy generated by the reproducing magnetic field Fr.

  Further, in the rear process shown in a partially enlarged manner in FIG. 9, an arrow F4 is a domain wall driving force due to a temperature gradient characteristic on the rear side in the moving direction of the laser beam spot for reproduction, and is represented by the above-described formula 2. . On the other hand, an arrow F3 in the figure is a domain wall driving force by Zeeman energy generated by the reproducing magnetic field Fr.

Now, the difference in temperature gradient characteristics described above,
From (temperature gradient characteristics used in the front process)> (temperature gradient characteristics used in the rear process), it can be said that there is a reproducing magnetic field strength satisfying F1> F2 and F3> F4. Therefore, by selecting a reproducing magnetic field strength that satisfies F1> F2 and F3> F4, it is possible to suppress the domain wall motion 111B in the rear process and cause only the domain wall motion 111A in the front process.

  Next, the magneto-optical recording medium of Conventional Example 2 will be described with reference to FIG.

  FIG. 10 is a block diagram showing a magneto-optical recording medium of Conventional Example 2.

  The magneto-optical recording medium 200 of Conventional Example 2 shown in FIG. 10 is disclosed in the above-mentioned Patent Document 2 (Japanese Patent Laid-Open No. 2003-51143). Here, the wavelength is about 400 nm to 450 nm during recording and reproduction. By using a blue laser beam, ultra-high density on the magneto-optical recording medium 200 is achieved.

  That is, in the magneto-optical recording medium 200 of Conventional Example 2, the first dielectric layer 202, the recording layer R including the first to third magnetic layers 203 to 205, and the second dielectric layer are formed on the light transmissive substrate 201. 206, a metal thermal diffusion layer 207, and a protective layer 208 are sequentially laminated, and the metal thermal diffusion layer 207 is configured as a single layer made of any one of Au, Ag, and Cu, and the second dielectric By setting the film thickness of the body layer 206 to 3 to 10 nm, the thermal diffusion in the recording layer R is sufficiently performed, so that the temperature of the recording layer R is not increased, and the decrease in the Kerr rotation angle is suppressed and stable and good. As a result, the effect of widening the power margin during reproduction due to the effect of thermal diffusion is obtained, and as a result, the recording / reproducing operation margin is expanded and a wide system margin can be realized. ing.

  Incidentally, in the conventional example 1, in the signal reproduction method of the magneto-optical recording medium 100 having the first to third magnetic layers 101 to 103, as described above, when a red laser beam having a wavelength of about 680 nm is applied, By irradiating a laser beam in a spot shape while applying a reproducing magnetic field Fr on the surface of the magneto-optical recording medium 100 during reproduction, the domain wall of the first magnetic layer 101 is formed at the front end in the moving direction of the reproducing laser beam spot. 110 is moved to the high temperature side in the temperature region to cause the domain wall motion 111A, while the domain wall 110 of the first magnetic layer 101 is moved to the high temperature side in the temperature region at the rear end in the moving direction of the laser beam spot for reproduction. Although it can be improved so that the domain wall motion 111B does not occur, the blue wavelength of 450 nm or less shorter than the red laser beam is used. If you want the information signal on the magneto-optical recording medium and reproducing super high density recording by using a Zabimu, the improvement measures against the rear process according only the application of the reproducing magnetic field Fr described above it is inadequate for the reasons described below.

  Here, FIG. 11 compares the temperature gradient characteristics of the red laser beam spot irradiated on the magneto-optical recording medium and the blue laser beam spot irradiated on the magneto-optical recording medium when reproducing the magneto-optical recording medium. FIG.

  In FIG. 11, the horizontal axis represents the center of each beam spot when the red laser beam spot and the blue laser beam spot are moved at a linear velocity of 3.0 m / sec, and the traveling direction of each beam spot is normal. And the vertical axis represents the temperature (K) of each beam spot.

  As described above, the magnetic domain expansion reproduction technique by the domain wall movement is to regenerate by expanding the short recording mark by moving the domain wall using the temperature distribution in the laser beam spot, that is, the temperature gradient characteristic. If the wavelength of the laser beam is shortened and the size of the laser beam spot is reduced to improve the recording density in the track direction, the temperature gradient characteristics in the laser beam spot will change during playback. It becomes difficult to produce a bonding film.

  In other words, the change in the temperature gradient characteristic is due to the change in the energy density depending on the wavelength of the laser beam. In the case of a red laser beam spot having a wavelength of about 680 nm and the case of a blue laser beam spot having a wavelength of 450 nm or less. Then, as shown in FIG. 11, the temperature gradient characteristic changes greatly, and the temperature gradient characteristic with respect to the position of the short wavelength blue laser beam spot is a long wavelength red laser beam spot due to the difference in beam diameter and energy density. Compared with the temperature gradient characteristic of the position of the region, it is considerably steep.

  In this case, when the domain wall motion detection is performed using the difference of the domain wall energy of the moving domain wall due to the temperature gradient characteristic, the steep temperature gradient characteristic in the blue laser beam spot increases the domain wall driving force. Become. This situation creates a surface that works favorably and disadvantageously for domain wall motion detection. The advantage is that the domain wall motion of the front process is agile, the deviation of the jitter of the reproduced signal on the time axis can be reduced, and the reproduced signal quality is improved. On the other hand, a disadvantage is that the domain wall movement is likely to occur in the aforementioned unnecessary rear process.

  Therefore, when the blue laser beam spot is irradiated onto the magneto-optical recording medium during reproduction, it becomes difficult to suppress the domain wall movement of the unnecessary rear process described above, and there is a problem in improving the track density by shortening the wavelength. It becomes.

  On the other hand, the magneto-optical recording medium 200 of Conventional Example 2 has high thermal conductivity between the second dielectric layer 206 and the protective layer 208 when recording and reproducing using a blue laser beam of about 400 nm to 450 nm. Although the thermal diffusion in the recording layer R is sufficiently performed by forming the metal diffusion layer 207 composed of any one of Au, Ag, and Cu, the temperature rise of the recording layer R is eliminated. Au, Ag, and Cu, which are high, are not metals for taking measures to improve the rear process described above.

  Further, in the magneto-optical recording medium 200 of the conventional example 2, the track pitch of the recording track formed on the substrate has been recently developed and set to a Blu-ray Disc track pitch of about 320 nm using a blue laser beam to achieve an ultra-high density. However, when the track pitch is set to about half of the track pitch of 320 nm (for example, about 160 nm) of the Blu-ray Disc in order to achieve a much higher density than the Blu-ray Disc, the blue laser beam It has been found that good recording / reproduction cannot be performed because the spot due to interference interferes with adjacent tracks.

  Therefore, in the magneto-optical recording medium in which at least three magnetic layers for enlarging and reading out the magnetic domain by domain wall movement are laminated, the track pitch of the recording track formed on the substrate of the magneto-optical recording medium is set to Blu-ray Disc. A magneto-optical recording medium and a magneto-optical recording medium capable of obtaining good recording / reproducing characteristics even when the magneto-optical recording medium is irradiated with a blue laser beam spot having a wavelength of 450 nm or less, which is set to about half the track pitch. A manufacturing method is desired.

The present invention has been made in view of the above problems, and the invention according to claim 1 is characterized in that a convex land corresponding to a recording track for recording and reproducing information signals protrudes toward the incident side of the laser beam spot. And at least three magnetic layers for enlarging and reading out the magnetic domain by moving the domain wall on the substrate formed in a spiral shape or concentric shape at a predetermined track pitch and having concave grooves formed on both sides of the land. In the laminated magneto-optical recording medium,
In-plane magnetic anisotropy between the first magnetic layer on which the laser beam spot is incident and the second magnetic layer located below the first magnetic layer and only on both sides of the recording track. The magneto-optical recording medium is characterized in that an in-plane magnetic anisotropic layer is formed.

According to a second aspect of the present invention, in the optical recording medium of the first aspect,
The in-plane magnetic anisotropic layer is a magneto-optical recording medium characterized in that it is a thin film of any one of Fe, Co alone, an alloy of rare earth metal and Fe, and an alloy of rare earth metal and Co.

Further, in the invention described in claim 3, the convex land corresponding to the recording track for recording / reproducing the information signal protrudes toward the incident side of the laser beam spot so as to be spiral or concentric with a predetermined track pitch. In a method of manufacturing a magneto-optical recording medium, wherein at least three or more magnetic layers for enlarging and reading a magnetic domain by domain wall movement are stacked on a substrate formed and formed with concave grooves on both sides of the land. ,
An in-plane magnetic anisotropy layer having in-plane magnetic anisotropy is formed on the second magnetic layer located below the first magnetic layer on the side where the laser beam spot is incident. The convex land and the concave groove An in-plane magnetic anisotropic layer film forming step to form a film,
Irradiation of an ion beam from above the in-plane magnetic anisotropic layer removes the in-plane magnetic anisotropic layer portion formed in a convex shape corresponding to the recording track, and on both sides of the recording track. An ion milling process that leaves an in-plane magnetic anisotropic layer portion formed into a concave shape;
A first magnetic layer forming step of forming the first magnetic layer after finishing the ion milling step;
A method for producing a magneto-optical recording medium, comprising:

  According to the magneto-optical recording medium of the present invention, in particular, in the magneto-optical recording medium in which at least three magnetic layers for enlarging and reading the magnetic domain by domain wall movement are laminated, the first laser beam incident side is provided. Since the in-plane magnetic anisotropy layer having in-plane magnetic anisotropy is formed between the magnetic layer and the second magnetic layer located below the first magnetic layer and only on both sides of the recording track, When the mark expansion direction of the recording track extends not only in the track direction but also in the radial direction, the reproduction signal can be obtained satisfactorily because the amount of jitter is small despite the narrow track recording.

  Further, according to the method of manufacturing a magneto-optical recording medium according to the present invention, in particular, in the method of manufacturing a magneto-optical recording medium in which at least three magnetic layers for enlarging and reading a magnetic domain by domain wall movement are stacked, An in-plane magnetic anisotropy layer having in-plane magnetic anisotropy is formed on the second magnetic layer located below the first magnetic layer on the side where the spot is incident, following the convex land and concave groove of the substrate. In-plane magnetic anisotropy layer forming process, and in-plane magnetic anisotropy formed in a convex shape corresponding to the recording track by irradiating an ion beam from above the in-plane magnetic anisotropic layer An ion milling process that leaves the in-plane magnetic anisotropic layer part formed in a concave shape on both sides of the recording track while removing the layer part, and a first magnetic layer is formed after the ion milling process is completed. A magnetic layer forming step, Therefore, in-plane magnetic anisotropy is formed between the first magnetic layer on the side where the laser beam spot is incident and the second magnetic layer located below the first magnetic layer and only on both sides of the recording track. It is possible to form an in-plane magnetic anisotropic layer having

  Hereinafter, an embodiment of a magneto-optical recording medium and a method for producing the magneto-optical recording medium according to the present invention will be described in detail in the order of Embodiment 1 and Embodiment 2 with reference to FIGS.

1 is a longitudinal sectional view schematically showing a magneto-optical recording medium of Example 1 according to the present invention,
FIG. 2 schematically shows a process of performing ion milling on the in-plane magnetic anisotropic layer formed on the second magnetic layer when manufacturing the magneto-optical recording medium of Example 1 according to the present invention. (A) shows an ion milling start state, (b) is a diagram showing an ion milling end state,
FIG. 3 is a perspective view schematically showing a reproduction state of the magneto-optical recording medium of Example 1 according to the present invention.

  As shown in FIG. 1, in the magneto-optical recording medium 10 of Example 1 according to the present invention, three magnetic layers 16, 14, and 13 for laminating and reading out magnetic domains by domain wall movement are laminated on a substrate 11. The three magnetic layers 16, 14, and 13 have perpendicular magnetic anisotropy and are sequentially magnetically coupled and stacked.

  On the substrate 11, the track pitch P of the recording track T for recording and reproducing information signals is set to about half (about 160 nm) with respect to the track pitch 320 nm of the recently developed Blu-ray Disc. And formed on the substrate 11 between the first magnetic layer 16 on the side on which the laser beam spot having a wavelength of 400 to 450 nm is incident and the second magnetic layer 14 positioned below the first magnetic layer 16. The in-plane magnetic anisotropy layers 15 and 15 having in-plane magnetic anisotropy are formed only on both sides of the recording track T corresponding to the convex land 11a corresponding to the concave grooves 11b and 11b formed on the substrate 11. As a result of the formation, the mark enlargement direction of the recording track T extends not only in the track direction but also in the radial direction, so that reproduction is possible despite the narrow track recording. And it is characterized in that it is configured to obtain good without jitter of No..

  In the magneto-optical recording medium 10 of Example 1 according to the present invention described above, the substrate 11 is formed in a disk shape with a thickness of 1.1 mm, an outer diameter of 120 mm, and a center hole diameter of 15 mm using a polycarbonate resin. A convex land 11a corresponding to the recording track T is projected on the substrate 11 at a slight height toward the incident side of the laser beam spot, and is formed in a spiral shape or a concentric shape at a predetermined track pitch P. Concave grooves 11b and 11b are formed on both sides of the land 11a. In other words, the convex lands 11a and the concave grooves 11b are alternately formed on the substrate 11.

  At this time, the pitch P of the recording tracks T formed corresponding to the convex lands 11a protruding on the substrate 11 at a slight height is set to about 160 nm as described above, and the recording is performed. The track width W of the track T is set to about 50 nm.

  In addition, on the substrate 11 having a thickness of 1.1 mm, the in-plane magnetic difference disposed only on both sides of the second dielectric layer 12, the third magnetic layer 13, the second magnetic layer 14, and the recording track T is provided. The isotropic layers 15, 15, the first magnetic layer 16, and the first dielectric layer 17 are sequentially formed in this order, and further, light is transmitted on the first dielectric layer 17 with a thickness of about 0.1 mm. A cover layer 18 having a magnetic property is attached so that a laser beam spot having a wavelength of 400 to 450 nm is irradiated toward the recording track T from the cover layer 18 side, and a reproducing magnetic field Fr is applied by a magnetic head (not shown). It is configured.

  Here, the above-described layers will be described in the order of film formation. First, the second dielectric layer 12 formed first on the substrate 11 is, for example, AlN having a high thermal conductivity of about 14.4 W / mK. The film is formed using a transparent dielectric material. At this time, the second dielectric layer 12 is alternately formed in a convex shape and a concave shape following the convex land 11 a and the concave groove 11 b formed alternately on the substrate 11.

  Next, the third magnetic layer 13 formed on the second dielectric layer 12 vertically irradiates a recording mark corresponding to an information signal by an external magnetic field from a magnetic head (not shown) while irradiating a blue laser beam spot during recording. After recording in the form of a magnetic domain (magnetization reversal region) on the film surface having the easy axis of magnetization in a certain direction, it has sufficient coercive force to stably hold the magnetic domain recorded at room temperature, and the information signal The film needs to have a Curie temperature Tc13 suitable for recording, and functions as a recording layer (memory layer).

  The third magnetic layer 13 is formed as a film having an easy magnetization direction in the vertical direction (direction perpendicular to the film surface), that is, an amorphous thin film made of heavy rare earth-iron group metal to be a so-called perpendicular magnetization film. Using a material based on the -Fe-Co film or Dy-Fe-Co film, and further adding a nonmagnetic element such as Al or Cr or Co to adjust the Curie temperature Tc13 of the third magnetic layer 13 Yes. At this time, the third magnetic layer 13 is also alternately formed in a convex shape and a concave shape following the convex land 11a and the concave groove 11b formed alternately on the substrate 11 via the second dielectric layer 12. ing.

  Next, the second magnetic layer 14 formed on the third magnetic layer 13 is an exchange that controls the exchange coupling force when the magnetic domain (record mark) is transferred from the third magnetic layer 13 to the first magnetic layer 16. It functions as a bonding force control layer. The second magnetic layer 14 is also formed as a film having an easy magnetization direction in the vertical direction (direction perpendicular to the film surface), that is, an amorphous thin film made of heavy rare earth-iron group metal to be a so-called perpendicular magnetization film. Using a material based on the -Fe film or Dy-Fe film, the Curie temperature Tc14 of the second magnetic layer 14 is set by adding a non-magnetic element such as Al or Cr or Co with rare earth metal predominance (RE-rich). The film is formed while adjusting. At this time, the second magnetic layer 14 also has convex and concave shapes following convex lands 11a and concave grooves 11b alternately formed on the substrate 11 via the second dielectric layer 12 and the third magnetic layer 13. The films are alternately formed.

  Next, the in-plane magnetic anisotropic layer 15 formed on the second magnetic layer 14 is the same as the magnetic layer formed by being magnetized in the longitudinal direction of a known magnetic tape, and Fe and Co alone. Any one of an alloy of rare earth metal and Fe and an alloy of rare earth metal and Co is formed on the thin film. At this time, the in-plane magnetic anisotropic layer 15 is also formed with convex lands 11 a and concave shapes alternately formed on the substrate 11 via the second dielectric layer 12, the third magnetic layer 13, and the second magnetic layer 14. The film is alternately formed in a convex shape and a concave shape following the groove 11b.

  Here, after the in-plane magnetic anisotropic layer 15 is formed, ion milling is performed as shown in FIGS.

  First, as shown in FIG. 2A, the substrate 11 on which the in-plane magnetic anisotropic layer 15 is formed is inserted into an unillustrated ion milling apparatus and accelerated from above the in-plane magnetic anisotropic layer 15. The in-plane magnetic anisotropic layer 15 irradiated with the xenon ion beam on the in-plane magnetic anisotropic layer 15 and formed into a convex shape following the convex land 11a of the substrate 11 by the xenon ion beam. Is removed until the second magnetic layer 14 is reached, but the in-plane magnetic anisotropic layer portion formed in the concave shape following the concave groove 11b of the substrate 11 is formed in the in-plane magnetic field formed in the convex shape. Since it is lower than the anisotropic layer part, it remains as it is.

  When the ion milling process is completed, as shown in FIG. 2B, the portion corresponding to the convex land 11a of the substrate 11 exposes the second magnetic layer 14 corresponding to the recording track T, and The left and right in-plane magnetic anisotropic layers 15 and 15 remain in the portions corresponding to the concave grooves 11b and 11b of the substrate 11, and the second magnetic layer 14 and the left and right in-plane magnetic anisotropic layers 15 are left. , 15 are flat surfaces having substantially the same height.

  Returning to FIG. 1, after ion milling is finished, a flat surface is formed on the second magnetic layer 14 corresponding to the recording track T and on the in-plane magnetic anisotropic layers 15, 15 located on the left and right of the second magnetic layer 14. The first magnetic layer 16 is formed on the incident side of the blue laser beam spot and has a magnetic gradient in order to facilitate the movement of the domain wall due to the temperature gradient characteristic created by the irradiation of the blue laser beam spot. It is a film having a small directionality and functions as a domain wall motion layer.

  The first magnetic layer 16 described above is formed as a film having an easy magnetization direction in the vertical direction (direction perpendicular to the film surface), an amorphous thin film made of heavy rare earth-iron group metal to be a so-called perpendicular magnetization film, A material based on a Gd-Fe film or a Gd-Fe-Co film is used, and the Curie temperature Tc16 of the first magnetic layer 16 is adjusted by adding a nonmagnetic element such as Al or Cr or Co. . When adjusting the magnetic characteristics in the temperature range where the domain wall motion described above is realized, it is effective to add an element that has the effect of reducing the exchange energy between the rare earth (Gd) and the iron group (Fe, Co). In this case, Bi, Sn, or the like can be applied as the additive element.

  Next, the first dielectric layer 17 formed on the first magnetic layer 16 has a thermal conductivity of 28.8 W / mK of the Tb—Fe—Co metal film used for the third magnetic layer 13 serving as the recording layer. The film is formed using a transparent dielectric material such as AlN having a high thermal conductivity of about 14.4 W / mK, for example, and has a light transmittance of about 0.1 mm. A cover layer 18 is attached.

  The first, second and third magnetic layers 16, 14, and 13 configured as described above are first and second in consideration of the temperature rise state during recording and reproduction due to the blue laser beam spot. The Curie temperatures Tc16, Tc14, and Tc13 of the third magnetic layers 16, 14, and 13 are preferably set in the vicinity of about 480K, about 420K, and about 590K.

  Here, the Curie temperatures Tc16, Tc14, and Tc13 of the first, second, and third magnetic layers 16, 14, and 13 increase the Curie temperature by increasing the amount of Co added in each magnetic layer. On the other hand, the Curie temperature can be lowered by increasing the amount of addition of a nonmagnetic element such as Al or Cr that does not significantly change the magnetic properties of each magnetic layer. The Curie temperatures Tc16, Tc14, and Tc13 of the first, second, and third magnetic layers 16, 14, and 13 are set so as to satisfy Tc13> Tc16> Tc14 by adjusting the amount of addition of Co and nonmagnetic elements. Yes.

  The film thicknesses t16, t14, and t13 of the first, second, and third magnetic layers 16, 14, and 13 are desirably set in the vicinity of about 30 nm, about 10 nm, and about 80 nm, respectively.

  FIG. 1 and FIG. 3 show a case where an information signal is recorded and reproduced on the magneto-optical recording medium 10 of the first embodiment configured as described above with a blue laser beam having a wavelength of 450 nm or less at an extremely high density. As shown, the recording mark corresponding to the information signal has an easy magnetization axis in the vertical direction by an external magnetic field from a magnetic head (not shown) while irradiating a blue laser beam spot from the light transmissive cover layer 18 side during recording. After recording in the form of magnetic domains on the third magnetic layer 13, the magnetic domains are exchange-coupled to the first magnetic layer 16 via the second magnetic layer 14, and a reproducing magnetic field Fr from a magnetic head (not shown) is applied during reproduction. The magnetization of the second magnetic layer 14 disappears due to the temperature rise due to the irradiation of the blue laser beam spot, and a domain wall is moved so as to expand the magnetic domain exchange-coupled in the first magnetic layer 16, thereby reproducing the reproduction mark. To have.

  Particularly in the first embodiment, as shown in an enlarged view in FIG. 3, the track width W of the recording track T is reduced to about 50 nm to narrow the recording track, and the first magnetic layer 16 on the side on which the blue laser beam spot is incident, In-plane magnetic anisotropic layers 15 and 15 having in-plane magnetic anisotropy between the second magnetic layer 14 located below the first magnetic layer 16 and only on both sides of the recording track T are provided. Because of the formation, the mark expansion direction of the recording track T extends not only in the track direction but also in the radial direction.

  At this time, the in-plane magnetic anisotropy layer 15 having in-plane magnetic anisotropy exists only on both sides of the recording track T, and when the magnetization direction of each magnetic layer is indicated by an arrow, The first magnetic layer 16 exchange-coupled with the in-plane magnetic anisotropic layers 15 and 15 provided on both sides and on the in-plane magnetic anisotropic layers 15 and 15 has a magnetic spin in the in-plane direction as shown in FIG. Since the in-plane magnetization film is oriented, the boundary on both sides of the recording track T of the recording mark transferred from the third magnetic layer 13 to the first magnetic layer 16 via the second magnetic layer 14 is in-plane. It is a so-called 90 ° domain wall that spins vertically.

  Therefore, the domain wall energy stored in the 90 ° domain wall is smaller than the energy stored in the 180 ° domain wall (region in which the magnetic spin rotates 180 °) in the perpendicular magnetization film that exists in the track direction. It is easy to move to a lower temperature side that is more energetically stable under a high temperature gradient, can be efficiently expanded in the radial direction, and exists in a completely recorded state in the region of the in-plane magnetic anisotropic layer 15. It is not necessary, and it is sufficient if the track width W of the recording track T is maintained. Along with this, even when the area immediately below the in-plane magnetic anisotropic layer 15 is cross-erased during recording, no trouble is caused in maintaining and expanding the recorded information.

Here, in Table 1 below, as a comparative example, when the track pitch is set to 320 nm and the in-plane magnetic anisotropic layer is not provided, and as in Example 1, the track pitch is set to 160 nm and the in-plane magnetic field is set. In the case where the anisotropic layer 15 was provided, the jitter characteristics of the reproduced signal were compared.

  As is apparent from Table 1, in Example 1, compared with the comparative example, the jitter amount was smaller than that in the comparative example despite the extremely narrow track pitch, so that it was confirmed that a reproduced signal could be obtained satisfactorily. .

FIG. 4 is a longitudinal sectional view schematically showing a magneto-optical recording medium of Example 2 according to the present invention.
FIG. 5 schematically shows a process of performing ion milling on the in-plane magnetic anisotropic layer formed on the second magnetic layer when manufacturing the magneto-optical recording medium of Example 2 according to the present invention. (A) shows an ion milling start state, (b) is a diagram showing an ion milling end state,
FIG. 6 is a perspective view schematically showing a reproduction state of the magneto-optical recording medium according to the second embodiment of the present invention.

  As shown in FIG. 4, the magneto-optical recording medium 20 according to the second embodiment of the present invention includes four layers of magnetic layers 27, 25, 24, and 23 for reading out a magnetic domain by moving a domain wall on a substrate 21. The four magnetic layers 27, 25, 24, and 23 have perpendicular magnetic anisotropy and are sequentially magnetically coupled and stacked.

  On the substrate 21, the track pitch P of the recording track T for recording and reproducing information signals is set to about half (about 160 nm) with respect to the track pitch 320 nm of the recently developed Blu-ray Disc. And formed on the substrate 21 between the first magnetic layer 27 on the side on which the laser beam spot having a wavelength of 400 to 450 nm is incident and the second magnetic layer 25 positioned below the first magnetic layer 27. The in-plane magnetic anisotropy layers 26, 26 having in-plane magnetic anisotropy are formed only on both sides of the recording track T corresponding to the convex land 21a corresponding to the concave grooves 21b, 21b formed on the substrate 21. As a result of the formation, the mark enlargement direction of the recording track T extends not only in the track direction but also in the radial direction, so that reproduction is possible despite the narrow track recording. And it is characterized in that it is configured to obtain satisfactorily without jitter of No..

  In the magneto-optical recording medium 20 according to the second embodiment of the present invention described above, the substrate 21 is formed in a disk shape with a thickness of 1.1 mm, an outer diameter of 120 mm, and a center hole diameter of 15 mm using a polycarbonate resin or the like as in the first embodiment. Further, a convex land 21a corresponding to the recording track T projects on the substrate 21 at a slight height toward the incident side of the laser beam spot, and is spiral or concentric with a predetermined track pitch P. The concave grooves 21b and 21b are formed on both sides of the convex land 21a. In other words, the convex land 21a and the concave groove 21b are alternately formed on the substrate 21. .

  At this time, the pitch P of the recording tracks T formed corresponding to the convex lands 21a protruding and formed on the substrate 21 at a slight height is set to about 160 nm as described above, and the recording is performed. The track width W of the track T is set to about 50 nm.

  Further, on the substrate 21 having a thickness of 1.1 mm, the second dielectric layer 12, the fourth magnetic layer 23, the third magnetic layer 24, the second magnetic layer 25, and only on both sides of the recording track T are provided. The arranged in-plane magnetic anisotropic layers 26, 26, the first magnetic layer 27, and the first dielectric layer 28 are sequentially formed in this order, and the thickness is further formed on the first dielectric layer 28. A cover layer 29 having a light transmittance of about 0.1 mm is attached, and a laser beam spot having a wavelength of 400 to 450 nm is irradiated toward the recording track T from the cover layer 29 side.

  Here, the respective layers described above will be described in the order of film formation. First, the second dielectric layer 22 formed first on the substrate 21 is, for example, AlN having a high thermal conductivity of about 14.4 W / mK. The film is formed using a transparent dielectric material. At this time, the second dielectric layer 12 is alternately formed into a convex shape and a concave shape following the convex land 21 a and the concave groove 21 b formed alternately on the substrate 21.

  Next, the fourth magnetic layer 23 formed on the second dielectric layer 22 vertically irradiates a recording mark corresponding to an information signal by an external magnetic field from a magnetic head (not shown) while irradiating a blue laser beam spot during recording. After recording in the form of a magnetic domain (magnetization reversal region) on the film surface having the easy axis of magnetization in a certain direction, it has sufficient coercive force to stably hold the magnetic domain recorded at room temperature, and the information signal The film must have a Curie temperature Tc23 suitable for recording, and functions as a recording layer (memory layer).

  The fourth magnetic layer 23 is formed as a film having an easy magnetization direction in the vertical direction (direction perpendicular to the film surface), that is, an amorphous thin film made of a heavy rare earth-iron group metal serving as a so-called perpendicular magnetization film. Using a material based on the -Fe-Co film or Dy-Fe-Co film, and further adding a nonmagnetic element such as Al or Cr or Co to adjust the Curie temperature Tc23 of the fourth magnetic layer 23 Yes. At this time, the fourth magnetic layer 23 is also alternately formed in a convex shape and a concave shape following the convex land 21a and the concave groove 21b formed alternately on the substrate 21 via the second dielectric layer 22. ing.

  Next, the third magnetic layer 24 formed on the fourth magnetic layer 23 and the second magnetic layer 25 formed on the third magnetic layer 24 are the same as the magneto-optical recording medium 10 of Example 1 described above. Unlike the second magnetic layer 14 formed in FIG. 1, it is formed in two layers, and the second magnetic layer 25 of the second and third magnetic layers 25, 24 is formed in a very thin film. Thus, the second magnetic layer 25 has a function of improving the domain wall moving performance from the front in the moving direction of the blue laser beam spot in the temperature region (about 430 K to about 490 K) in which the domain wall can move. In 2, the application of the reproducing magnetic field Fr can be omitted.

  At least the third magnetic layer 24 of the second and third magnetic layers 25, 24 controls the exchange coupling force when the magnetic domain (record mark) is transferred from the fourth magnetic layer 23 to the first magnetic layer 27. Functions as an exchange coupling force control layer. The second and third magnetic layers 25 and 24 are also formed as films having an easy magnetization direction in the vertical direction (perpendicular to the film surface), an amorphous thin film made of a heavy rare earth-iron group metal to be a so-called perpendicular magnetization film. The second and third layers are made by adding a nonmagnetic element such as Al or Cr or Co with rare earth metal predominance (RE-rich) using a material based on a Tb-Fe film or a Dy-Fe film. The magnetic layers 25 and 24 are formed while adjusting the Curie temperatures Tc25 and Tc24, respectively. At this time, the second and third magnetic layers 25 and 24 also have convex lands 21a and concave grooves 21b alternately formed on the substrate 21 through the second dielectric layer 22 and the fourth magnetic layer 23. The film is alternately formed in a convex shape and a concave shape.

  Next, the in-plane magnetic anisotropic layer 26 formed on the second magnetic layer 25 is the same as the magnetic layer formed by being magnetized in the longitudinal direction of a known magnetic tape, and Fe and Co alone. Any one of an alloy of rare earth metal and Fe and an alloy of rare earth metal and Co is formed on the thin film. At this time, the in-plane magnetic anisotropic layer 26 is also a convex shape formed alternately on the substrate 21 via the second dielectric layer 22, the fourth magnetic layer 23, the third magnetic layer 24, and the second magnetic layer 25. The lands 21a and the concave grooves 21b are alternately formed into a convex shape and a concave shape.

  Here, after the in-plane magnetic anisotropic layer 26 is formed, ion milling is performed as shown in FIGS.

  First, as shown in FIG. 5A, a substrate 21 having an in-plane magnetic anisotropic layer 26 formed therein is inserted into an unillustrated ion milling apparatus, and from above the in-plane magnetic anisotropic layer 26. The in-plane magnetic anisotropic layer 26 irradiated with the accelerated xenon ion beam onto the in-plane magnetic anisotropic layer 26 and formed into a convex shape following the convex land 21a of the substrate 21 by the xenon ion beam. Although the portion is removed until it reaches the second magnetic layer 25, the in-plane magnetic anisotropic layer portion formed in a concave shape following the concave groove 21b of the substrate 21 is in the in-plane formed in a convex shape. Since it is lower than the magnetic anisotropic layer portion, it remains as it is.

  When the ion milling process is completed, the second magnetic layer 25 corresponding to the recording track T is exposed at the portion corresponding to the convex land 21a of the substrate 21, as shown in FIG. The left and right in-plane magnetic anisotropic layers 26 and 26 remain in the portions corresponding to the concave grooves 21b and 21b of the substrate 21, and the second magnetic layer 25 and the left and right in-plane magnetic anisotropic layers 26 are left. , 26 are flat surfaces having substantially the same height.

  Returning to FIG. 4, after ion milling is finished, a flat surface is formed on the second magnetic layer 25 corresponding to the recording track T and on the in-plane magnetic anisotropic layers 26 and 26 located on the left and right sides of the second magnetic layer 25. The first magnetic layer 27 is formed on the incident side of the blue laser beam spot and is magnetically different to facilitate the movement of the domain wall due to the temperature gradient characteristic created by the irradiation of the blue laser beam spot. It is a film having a small directionality and functions as a domain wall motion layer.

  The first magnetic layer 27 is formed as a film having an easy magnetization direction in the vertical direction (direction perpendicular to the film surface), that is, an amorphous thin film made of heavy rare earth-iron group metal to be a so-called perpendicular magnetization film, A material based on a Gd—Fe film or a Gd—Fe—Co film is used, and the Curie temperature Tc27 of the first magnetic layer 27 is adjusted by adding a nonmagnetic element such as Al or Cr or Co. . When adjusting the magnetic characteristics in the temperature range where the domain wall motion described above is realized, it is effective to add an element that has the effect of reducing the exchange energy between the rare earth (Gd) and the iron group (Fe, Co). In this case, Bi, Sn, or the like can be applied as the additive element.

  Next, the first dielectric layer 28 formed on the first magnetic layer 27 has a thermal conductivity of 28.8 W / mK of the Tb—Fe—Co metal film used for the fourth magnetic layer 23 serving as the recording layer. The film is formed using a transparent dielectric material such as AlN having a high thermal conductivity of about 14.4 W / mK, for example, and has a light transmittance of about 0.1 mm. A cover layer 29 is attached.

  In consideration of the temperature rise state during recording and reproduction by the blue laser beam spot for the first, second, third, and fourth magnetic layers 27, 25, 24, and 23 configured as described above, The Curie temperatures Tc27, Tc25, Tc24, and Tc23 of the first, second, third, and fourth magnetic layers 27, 25, 24, and 23 can be set in the vicinity of about 480K, about 430K, about 420K, and about 590K. desirable.

  Here, the Curie temperatures Tc27, Tc25, Tc24, and Tc23 of the first, second, third, and fourth magnetic layers 27, 25, 24, and 23 increase the amount of Co added in each magnetic layer. The Curie temperature can be increased by increasing the amount of nonmagnetic elements such as Al and Cr that do not significantly change the magnetic properties of each magnetic layer. The Curie temperatures Tc27, Tc25, Tc24 of the first, second, third, and fourth magnetic layers 27, 25, 24, and 23 are adjusted by adjusting the amount of Co and nonmagnetic elements added to each magnetic layer. Tc23 is set to satisfy Tc23> Tc27> Tc25> Tc24.

  The film thicknesses t27, t25, t24, and t23 of the first, second, third, and fourth magnetic layers 27, 25, 24, and 23 are set to about 30 nm, about 5 nm, about 10 nm, and about 80 nm, respectively. It is desirable to do.

  FIG. 4 and FIG. 6 show a case where an information signal is recorded / reproduced on the magneto-optical recording medium 20 of the second embodiment configured as described above at a very high density using a blue laser beam having a wavelength of 450 nm or less. As shown, the recording mark corresponding to the information signal has an easy magnetization axis in the vertical direction by an external magnetic field from a magnetic head (not shown) while irradiating the blue laser beam spot from the light transmissive cover layer 29 side during recording. After recording in the form of magnetic domains on the fourth magnetic layer 23, the magnetic domains are exchange-coupled to the first magnetic layer 27 via the second and third magnetic layers 25 and 24, and the temperature rises by irradiation with a blue laser beam spot during reproduction. Thus, at least the magnetization of the third magnetic layer 24 disappears and the domain wall is moved so as to expand the magnetic domain exchange-coupled in the first magnetic layer 27 to obtain a reproduction mark.

  Particularly in the second embodiment, as shown in an enlarged view in FIG. 6, the track width W of the recording track T is reduced to about 50 nm to narrow the recording track, and the first magnetic layer 27 on the side on which the blue laser beam spot is incident, In-plane magnetic anisotropic layers 26 and 26 having in-plane magnetic anisotropy between the second magnetic layer 25 positioned below the first magnetic layer 27 and only on both sides of the recording track T are provided. Because of the formation, as in the first embodiment, the mark enlargement direction of the recording track T extends not only in the track direction but also in the radial direction, so that a reproduced signal can be obtained satisfactorily without jitter despite narrow track recording.

1 is a longitudinal sectional view schematically showing a magneto-optical recording medium of Example 1 according to the present invention. When manufacturing the magneto-optical recording medium of Example 1 which concerns on this invention, the process of performing an ion milling process with respect to the in-plane magnetic anisotropic layer formed into a film on the 2nd magnetic layer was shown typically. It is a longitudinal cross-sectional view, (a) shows an ion milling start state, (b) is a diagram showing an ion milling end state. 1 is a perspective view schematically showing a reproduction state of a magneto-optical recording medium of Example 1 according to the present invention. FIG. It is the longitudinal cross-sectional view which showed typically the magneto-optical recording medium of Example 2 which concerns on this invention. When manufacturing the magneto-optical recording medium of Example 2 which concerns on this invention, the process of performing an ion milling process with respect to the in-plane magnetic anisotropic layer formed into a film on the 2nd magnetic layer was shown typically. It is a longitudinal cross-sectional view, (a) shows an ion milling start state, (b) is a diagram showing an ion milling end state. It is the perspective view which showed typically the reproduction | regeneration state of the magneto-optical recording medium of Example 2 which concerns on this invention. In the prior art example 1, it is the figure typically shown in order to demonstrate the signal reproduction method of the magneto-optical recording medium which has the 1st-3rd magnetic layer, (a) shows a magneto-optical recording medium, (b) Is a medium temperature distribution, (c) is a diagram showing the force that causes the domain wall movement. In Conventional Example 1, when a reproducing magnetic field is applied to a magneto-optical recording medium, it is a diagram schematically showing a front process on the front side in the moving direction of a laser beam spot. In Conventional Example 1, when a reproducing magnetic field is applied to a magneto-optical recording medium, it is a diagram schematically showing a rear process on the rear side in the moving direction of a laser beam spot. FIG. 6 is a configuration diagram showing a magneto-optical recording medium of Conventional Example 2. FIG. 5 is a diagram comparing temperature gradient characteristics of a red laser beam spot irradiated on a magneto-optical recording medium and a blue laser beam spot irradiated on a magneto-optical recording medium when reproducing a magneto-optical recording medium.

Explanation of symbols

10 ... magneto-optical recording medium of Example 1,
11 ... Substrate, 11a ... Land, 11b ... Groove,
12 ... 2nd dielectric layer, 13 ... 3rd magnetic layer, 14 ... 2nd magnetic layer,
15 ... In-plane magnetic anisotropic layer, 16 ... First magnetic layer, 17 ... First dielectric layer, 18 ... Cover layer,
20 ... magneto-optical recording medium of Example 2,
21 ... Substrate, 21a ... Land, 21b ... Groove,
22 ... 2nd dielectric layer, 23 ... 4th magnetic layer, 24 ... 3rd magnetic layer, 25 ... 2nd magnetic layer,
26 ... In-plane magnetic anisotropic layer, 27 ... First magnetic layer, 28 ... First dielectric layer, 29 ... Cover layer,
T ... recording track, P ... track pitch, W ... track width.

Claims (3)

Convex lands corresponding to recording tracks for recording / reproducing information signals project toward the incident side of the laser beam spot and are formed in a spiral or concentric shape at a predetermined track pitch, and on both sides of the lands In a magneto-optical recording medium in which at least three magnetic layers for enlarging and reading a magnetic domain by domain wall movement are laminated on a substrate on which a concave groove is formed,
In-plane magnetic anisotropy between the first magnetic layer on which the laser beam spot is incident and the second magnetic layer located below the first magnetic layer and only on both sides of the recording track. A magneto-optical recording medium comprising an in-plane magnetic anisotropic layer.   2. The magneto-optical recording medium according to claim 1, wherein the in-plane magnetic anisotropic layer is a thin film of any one of Fe, Co alone, an alloy of rare earth metal and Fe, and an alloy of rare earth metal and Co. Convex lands corresponding to recording tracks for recording / reproducing information signals project toward the incident side of the laser beam spot and are formed in a spiral or concentric shape at a predetermined track pitch, and on both sides of the lands In the method of manufacturing a magneto-optical recording medium in which at least three magnetic layers for enlarging and reading a magnetic domain by domain wall movement are laminated on a substrate on which a concave groove is formed.
An in-plane magnetic anisotropy layer having in-plane magnetic anisotropy is formed on the second magnetic layer located below the first magnetic layer on the side where the laser beam spot is incident. The convex land and the concave groove An in-plane magnetic anisotropic layer film forming step to form a film,
Irradiation of an ion beam from above the in-plane magnetic anisotropic layer removes the in-plane magnetic anisotropic layer portion formed in a convex shape corresponding to the recording track, and on both sides of the recording track. An ion milling process that leaves an in-plane magnetic anisotropic layer portion formed into a concave shape;
A first magnetic layer forming step of forming the first magnetic layer after finishing the ion milling step;
A method for producing a magneto-optical recording medium, comprising:

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