JP2006018943A - Method and device for recording/reproducing magneto-optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform the super high density recording/reproducing of a magneto-optical recording medium using a laser beam having a short wavelength. <P>SOLUTION: Rim intensity Rim of a laser beam spot BLS having the short wavelength for irradiating the magneto-optical recording medium when the reproduction is performed is defined as Rim=(the intensity with respect to the radial direction of the magneto-optical recording medium)/(the intensity with respect to the tangential direction of the magneto-optical recording medium). The method for reproducing the magneto-optical recording medium is provided, which is characterized in that the temperature gradient characteristic of the laser beam spot BLS having the short wavelength with respect to its position when the reproduction is performed is made so as to be close to the temperature gradient characteristic of a laser beam spot having a long wavelength with respect to the position, by setting the rim intensity Rim at 1 or more (Rim>1). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a magneto-optical recording medium recording / reproducing method and magneto-optical recording medium recording / reproducing capable of performing recording / reproducing of 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. It relates to the device.

  In the magneto-optical recording method, 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 an 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 of. In the magneto-optical recording / reproduction in which the magnetization reversed portion, that is, the information bit forms a magnetic domain and reads it out by the magnetic Kerr effect, the recording bit length (record mark length) is shortened, that is, the information in order to improve the recording density. When recording marks corresponding to signals 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 layers are magneto-optical recording using a red laser beam having a wavelength of about 680 nm while applying a reproducing magnetic field, using a magneto-optical recording medium comprising a magnetic film having a lower Curie temperature than the first magnetic layer and the third magnetic layer. 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 (see, for example, 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 Japanese Patent Application Laid-Open No. 2003-51143.

FIG. 6 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, wherein (a) shows 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. 7 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. 8 is a diagram schematically illustrating 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. FIG. First, the prior art example 1 shown in FIG. 6 to FIG. 8 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. 6A, 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 on the magneto-optical recording medium 100 in a spot shape. However, if the magneto-optical recording medium 100 side is fixed, the laser beam spot is fixed. 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. 6B. 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 movement 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. When called, the force F (x) that causes the domain wall motion 111B by the rear process is expressed by the following equation (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. 7, the arrow F1 is a domain wall driving force due to 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. 8, 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 reproducing laser beam spot, 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.

  From the above-mentioned difference in temperature gradient characteristics, (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. 9 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. 9 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 formed as a single layer made of any one of Au, Ag, and Cu, and the second dielectric By setting the film thickness of the 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, which is stable and good. C / N is obtained, and further, the effect of widening the power margin during reproduction due to the effect of thermal diffusion is obtained. As a result, it is shown that the recording / reproducing operation margin is expanded and a wide system margin can be realized. Yes.

  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. 10 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. 10, 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 / s, 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. 10, the temperature gradient characteristic changes greatly, and the temperature gradient characteristic of the short wavelength blue laser beam spot with respect to its position depends on 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 shift of the detection signal on the time axis of the Jitter detection signal can be reduced, and the detection signal quality is improved. On the other hand, the disadvantage is that the domain wall motion 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 unnecessary domain wall movement of the rear process, which causes a problem in improving the track density by shortening the wavelength. It becomes.

  On the other hand, in the magneto-optical recording medium 200 of Conventional Example 2, when recording / reproducing using a laser beam of about 400 nm to 450 nm, Au having a high thermal conductivity is provided between the second dielectric layer 206 and the protective layer 208. , Ag, and Cu, the metal diffusion layer 207 is formed to sufficiently diffuse the heat in the recording layer R, so that the temperature rise of the recording layer R is eliminated. High Au, Ag, and Cu are not metals for improving the rear process described above.

  Therefore, when a blue laser beam spot having a wavelength of 450 nm or less is irradiated onto the magneto-optical recording medium during reproduction, unnecessary rear process domain wall movement that occurs in the blue laser beam spot on the magneto-optical recording medium is surely suppressed. A magneto-optical recording medium recording / reproducing method and a magneto-optical recording medium recording / reproducing apparatus which can be used are desired.

According to the first aspect of the present invention, there is provided a magneto-optical recording medium in which at least three magnetic layers having functions of a domain wall motion layer, an exchange coupling force control layer, and a recording layer are laminated from the side irradiated with a laser beam spot having a short wavelength. When recording, a recording mark corresponding to an information signal was recorded in the form of a magnetic domain on the recording layer having an easy axis in the perpendicular direction by an external magnetic field from a magnetic head while irradiating the laser beam spot with a short wavelength during recording. Later, the magnetic domain is exchange-coupled to the domain wall moving layer through the exchange coupling force control layer, and the magnetic field is increased by irradiation with the short-wavelength laser beam spot while applying a reproduction magnetic field from the magnetic head as necessary during reproduction. When the magnetization of the exchange coupling force control layer disappears at a temperature and the domain domain exchange-coupled in the domain wall moving layer is expanded, domain wall movement is caused to obtain a reproduction mark. In the magneto-optical recording medium recording and reproducing method,
The rim intensity Rim of the short-wavelength laser beam spot irradiated onto the magneto-optical recording medium at the time of reproduction,
By defining Rim = intensity in the radial direction of the magneto-optical recording medium / intensity in the tangential direction of the magneto-optical recording medium, the rim intensity Rim is set to 1 or more (Rim> 1). The magneto-optical recording medium recording / reproducing method is characterized in that the temperature gradient characteristic of the laser beam spot with respect to the position thereof is made closer to the temperature gradient characteristic of the long wavelength laser beam spot with respect to the position.

According to a second aspect of the present invention, there is provided a magneto-optical recording in which at least three or more magnetic layers having the functions of a domain wall motion layer, an exchange coupling force control layer, and a recording layer are laminated from a side irradiated with a laser beam spot having a short wavelength. Using a medium, a recording mark corresponding to an information signal by an external magnetic field from a magnetic head while irradiating the laser beam spot with a short wavelength at the time of recording is recorded in the form of a magnetic domain in the recording layer having an easy axis in the perpendicular direction. After recording, the magnetic domain is exchange-coupled to the domain wall moving layer via the exchange coupling force control layer, and irradiation of the laser beam spot of the short wavelength while applying a reproduction magnetic field from the magnetic head as necessary during reproduction The magnetization of the exchange coupling force control layer disappears due to the temperature rise due to the magnetic field, and the domain wall is moved so as to expand the magnetic domain exchange-coupled in the domain wall moving layer. In the magneto-optical recording medium recording and reproducing apparatus for obtaining,
A semiconductor laser for emitting the short-wavelength laser beam;
A beam shaping element that expands only the tangential direction of the magneto-optical recording medium with respect to the short-wavelength laser beam emitted from the semiconductor laser;
An optical pickup including at least an objective lens that irradiates the magneto-optical recording medium with the short-wavelength laser beam spot obtained by narrowing the short-wavelength laser beam transmitted through the beam shaping element;
The rim intensity Rim of the short-wavelength laser beam spot irradiated onto the magneto-optical recording medium at the time of reproduction,
Rim = diameter intensity of the magneto-optical recording medium / intensity in the tangential direction of the magneto-optical recording medium When the rim intensity Rim is set to 1 or more (Rim> 1) by the beam shaping element, reproduction is performed. The magneto-optical recording medium recording / reproducing apparatus is characterized in that the temperature gradient characteristic of the short wavelength laser beam spot with respect to the position thereof is sometimes close to the temperature gradient characteristic of the long wavelength laser beam spot with respect to the position.

According to the magneto-optical recording medium recording / reproducing method and the magneto-optical recording medium recording / reproducing apparatus according to claim 1 and 2, particularly, the rim intensity Rim of the short-wavelength laser beam spot irradiated on the magneto-optical recording medium at the time of reproduction is obtained. ,
When defined as Rim = intensity in the radial direction of the magneto-optical recording medium / intensity in the tangential direction of the magneto-optical recording medium, the rim intensity Rim is set to 1 or more (Rim> 1) by the beam shaping element housed in the optical pickup. As a result, the temperature gradient characteristic of the short-wavelength laser beam spot (blue laser beam spot) at that position during reproduction was made closer to the temperature gradient characteristic of the long-wavelength laser beam spot (red laser beam spot) at that position. It suppresses unnecessary domain wall movement in the rear process, which occurs in the laser beam spot on the recording medium, and causes only domain wall movement in the front process, so that it is possible to improve the reproduction performance with a short wavelength laser beam. it can.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a magneto-optical recording medium recording / reproducing method and magneto-optical recording medium recording / reproducing apparatus according to the present invention will be described below with reference to FIGS. The magneto-optical recording medium recording / reproducing method and magneto-optical recording medium recording / reproducing apparatus> will be described in detail in this order.

<First and second magneto-optical recording media>
FIG. 1 is a sectional view schematically showing a first magneto-optical recording medium applied to a magneto-optical recording medium recording / reproducing method and a magneto-optical recording medium recording / reproducing apparatus according to the present invention,
FIG. 2 is a cross-sectional view schematically showing a second magneto-optical recording medium applied to the magneto-optical recording medium recording / reproducing method and magneto-optical recording medium recording / reproducing apparatus according to the present invention.

  Before describing the magneto-optical recording medium recording / reproducing method and magneto-optical recording medium recording / reproducing apparatus according to the present invention, the first and second magneto-optical recording media applied here will be described with reference to FIGS. explain.

  First, as shown in FIG. 1, a first magneto-optical recording medium 10 applied to a magneto-optical recording medium recording / reproducing method and a magneto-optical recording medium recording / reproducing apparatus according to the present invention has an outer shape of a disk and transmits an information signal. It is configured as an optical disc that can be recorded and reproduced at an extremely high density. In the first magneto-optical recording medium 10, a transparent first dielectric layer 12 and first to first layers having a three-layer structure are formed on a light-transmitting substrate 11 formed using a transparent glass plate or transparent polycarbonate. The third magnetic layers 13 to 15, the second dielectric layer 16, and the protective layer 17 are sequentially stacked.

  Here, each of the above-described layers will be described more specifically in order. The transparent first dielectric layer 12 on the light-transmitting substrate 11 is formed using a transparent dielectric material, and the transparent dielectric material 12 As the material, AlN or the like having a high thermal conductivity or SiN having a relatively low thermal conductivity but excellent protection performance is used.

  Of the first to third magnetic layers 13 to 15 having a three-layer structure on the transparent first dielectric layer 12, the first magnetic layer 13 on the irradiation side of the blue laser beam spot BLS is a blue laser beam. In order to facilitate the movement of the domain wall by the temperature gradient characteristic created by the irradiation of the spot BLS, the film has a small magnetic anisotropy and functions as a domain wall moving layer.

  The first magnetic layer 13 is formed as a film having an easy magnetization direction in the vertical 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 Tc11 of the first magnetic layer 13 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.

  The second magnetic layer 14 functions as an exchange coupling force control layer that controls the exchange coupling force when a magnetic domain (record mark) is transferred from the third magnetic layer 15 to the first magnetic layer 13. 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 -Fe film or Dy-Fe film, a nonmagnetic element such as Al or Cr or Co is added to form a film while adjusting the Curie temperature Tc12 of the second magnetic layer 14.

  In addition, the third magnetic layer 15 described above easily magnetizes a recording mark according to an information signal in a vertical direction by an external magnetic field from a magnetic head 36 (FIG. 3) described later while irradiating a blue laser beam spot BLS during recording. After recording in the form of magnetic domains (magnetization reversal areas) on the film surface with an axis, it has sufficient coercive force to stably hold the magnetic domains recorded at room temperature and suitable for recording information signals Further, the film needs to have a Curie temperature Tc13 and functions as a recording layer (memory layer).

  The third magnetic layer 15 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-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 15 Yes.

  Then, the first, second, and third magnetic layers 13 to 15 configured as described above are considered in consideration of the temperature rise state during recording and reproduction by the blue laser beam spot BLS. The Curie temperatures Tc11, Tc12, and Tc13 of the layers 13, 14, and 15 are desirably set in the vicinity of about 480K, about 420K, and about 590K. Here, the Curie temperatures Tc11, Tc12, Tc13 of the first, second, and third magnetic layers 13, 14, 15 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 Tc11, Tc12, and Tc13 described above are set such that Tc13> Tc11> Tc12 by adjusting the addition amount of Co and nonmagnetic elements. The film thicknesses t11, t12, and t13 of the first, second, and third magnetic layers 13, 14, and 15 are desirably set in the vicinity of about 30 nm, about 10 nm, and about 80 nm, respectively.

  The transparent second dielectric layer 16 on the third magnetic layer 15 is formed using a dielectric material that is substantially the same as the transparent first dielectric layer 12.

  Furthermore, the protective layer 17 on the second dielectric layer 16 is formed as necessary in order to protect the second dielectric layer 16 side using a UV curable resin material or the like.

  When the information signal is recorded / reproduced to / from the first magneto-optical recording medium 10 using the blue laser beam BL (FIG. 3) having a wavelength of 450 nm or less, the blue laser beam spot BLS is transmitted through the light during recording. Recording marks corresponding to the information signals were recorded in the form of magnetic domains on the third magnetic layer 15 having an easy axis in the perpendicular direction by an external magnetic field from the magnetic head 36 (FIG. 3) while irradiating from the conductive substrate 11 side. Later, the magnetic domain is exchange-coupled to the first magnetic layer 13 via the second magnetic layer 14, and the temperature is increased by irradiation with the blue laser beam spot BLS while applying the reproducing magnetic field Fr from the magnetic head 36 (FIG. 3) during reproduction. The reproduction mark is obtained by moving the domain wall so that the magnetization of the second magnetic layer 14 disappears and the exchange-coupled magnetic domain in the first magnetic layer 13 is expanded. Furthermore, by setting the rim intensity of the blue laser beam spot BLS during reproduction irradiated onto the first magneto-optical recording medium 10 from the objective lens 47 (FIG. 3) to an optimum value, the wavelength is 450 nm or less during reproduction. In the blue laser beam spot BLS on the first magneto-optical recording medium 10, the temperature gradient characteristic for the position of the blue laser beam spot BLS is brought close to the temperature gradient characteristic for the position of the red laser beam spot having a wavelength of about 680 nm. The magneto-optical recording medium recording / reproducing apparatus 30 (FIG. 3) is improved so as to suppress the domain wall movement in the unnecessary rear process and to cause only the domain wall movement in the front process.

  Next, as shown in FIG. 2, the second magneto-optical recording medium 20 applied to the magneto-optical recording medium recording / reproducing method and magneto-optical recording medium recording / reproducing apparatus according to the present invention also has an outer shape of a disc shape and an information signal. Is configured as an optical disc capable of recording and reproducing at an extremely high density. In the second magneto-optical recording medium 20, a transparent first dielectric layer 22 and first to first layers having a four-layer structure are formed on a light-transmitting substrate 21 formed by using a transparent glass plate or transparent polycarbonate. The fourth magnetic layers 23 to 26, the second dielectric layer 27, and the protective layer 28 are sequentially stacked.

  Here, each of the above-described layers will be described more specifically in order. The transparent first dielectric layer 22 on the light transmissive substrate 21 is formed using a transparent dielectric material, and the transparent dielectric layer 22 is transparent. As the material, AlN or the like having a high thermal conductivity or SiN having a relatively low thermal conductivity but excellent protection performance is used.

  Of the first to fourth magnetic layers 23 to 26 having a four-layer structure on the transparent first dielectric layer 22, the first magnetic layer 23 on the irradiation side of the blue laser beam spot BLS is a blue laser beam. In order to facilitate the movement of the domain wall by the temperature gradient characteristic created by the irradiation of the spot BLS, the film has a small magnetic anisotropy and functions as a domain wall moving layer.

  The first 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 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 Tc21 of the first magnetic layer 23 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.

  Unlike the second magnetic layer 14 formed on the first magneto-optical recording medium 10 described above, the second and third magnetic layers 24 and 25 are formed in two layers. By forming the second magnetic layer 24 out of the three magnetic layers 24 and 25 in a very thin film, the second magnetic layer 24 has a blue laser beam spot BLS in a temperature region (about 430 K to about 490 K) in which the domain wall can move. It has the function of suppressing the domain wall movement from the rear in the moving direction and improving the domain wall movement reproduction performance.

  At least the third magnetic layer 25 of the second and third magnetic layers 24 and 25 controls the exchange coupling force when the magnetic domain (record mark) is transferred from the fourth magnetic layer 26 to the first magnetic layer 23. Functions as an exchange coupling force control layer. The second and third magnetic layers 24 and 25 are also formed as films having an easy magnetization direction in the vertical direction (direction perpendicular to the film surface), that is, as amorphous thin films made of heavy rare earth-iron group metal to be a so-called perpendicular magnetization film. A Curie temperature Tc22 of the second and third magnetic layers 24 and 25 is added by using a material based on a Tb-Fe film or a Dy-Fe film and adding a nonmagnetic element such as Al or Cr or Co. , Tc23 are adjusted, respectively.

  Further, the fourth magnetic layer 26 described above easily magnetizes a recording mark corresponding to an information signal in a vertical direction by an external magnetic field from a magnetic head 36 (FIG. 3) described later while irradiating a blue laser beam spot BLS during recording. After recording in the form of magnetic domains (magnetization reversal areas) on the film surface with an axis, it has sufficient coercive force to stably hold the magnetic domains recorded at room temperature and suitable for recording information signals Further, the film needs to have a Curie temperature Tc24 and functions as a recording layer (memory layer).

  The fourth magnetic layer 26 is also formed as a film having an easy magnetization direction in the vertical 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 the -Fe-Co film or Dy-Fe-Co film is used, and a nonmagnetic element such as Al or Cr or Co is added to adjust the Curie temperature Tc24 of the fourth magnetic layer 26. Yes.

  The first, second, third, and third magnetic layers 23 to 26 configured as described above are first, second, third, and third, considering the temperature rise state during recording and reproduction by the blue laser beam spot BLS. The Curie temperatures Tc21, Tc22, Tc23, and Tc24 of the fourth magnetic layers 23, 24, 25, and 26 are desirably set in the vicinity of about 480K, about 430K, about 420K, and about 590K. Here, the Curie temperatures Tc21, Tc22, Tc23, and Tc24 of the first, second, third, and fourth magnetic layers 23, 24, 25, and 26 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 Tc21, Tc22, Tc23, and Tc24 are set such that Tc24> Tc21> Tc22> Tc23 by adjusting the amount of Co or nonmagnetic element added to each magnetic layer. The film thicknesses t21, t22, t23, and t24 of the first, second, third, and fourth magnetic layers 23, 24, 25, and 26 are about 30 nm, about 5 nm, about 10 nm, and about 80 nm, respectively. It is desirable to set.

  The transparent second dielectric layer 27 on the fourth magnetic layer 26 is formed using a dielectric material that is substantially the same as the transparent first dielectric layer 22.

  Further, the protective layer 28 on the second dielectric layer 27 is formed as necessary to protect the second dielectric layer 27 side using a UV curable resin material or the like.

  When the information signal is recorded and reproduced on the second magneto-optical recording medium 20 using the blue laser beam BL (FIG. 3) having a wavelength of 450 nm or less, the blue laser beam spot BLS is transmitted through the light during recording. In the form of magnetic domains in the fourth magnetic layer 26 having an easy axis in the perpendicular direction, the recording mark corresponding to the information signal is irradiated by an external magnetic field from a magnetic head 36 (FIG. 3) to be described later while irradiating from the conductive substrate 21 side. After recording, the magnetic domain is exchange-coupled to the first magnetic layer 23 via the second and third magnetic layers 24 and 25, and a blue laser beam spot is applied while applying a reproducing magnetic field Fr from the magnetic head 36 as necessary during reproduction. The temperature of the third magnetic layer 25 is lost by the temperature rise due to the irradiation of BLS, and the domain wall is moved so as to expand the magnetic domain exchange-coupled in the first magnetic layer 23, thereby reproducing the reproduction marker. In particular, the magnetic layer has a four-layer structure to improve the domain wall motion reproduction performance on the front side in the moving direction of the blue laser beam spot BLS, and as will be described later, the objective lens 47 (FIG. 3). ) To the optimal value for the rim intensity of the blue laser beam spot BLS during reproduction irradiated onto the second magneto-optical recording medium 20, the position of the blue laser beam spot BLS having a wavelength of 450 nm or less during reproduction is set to that position. In the unnecessary rear process that occurs in the blue laser beam spot BLS on the second magneto-optical recording medium 20, the temperature gradient characteristic with respect to the temperature of the red laser beam spot with a wavelength of about 680 nm is brought close to the temperature gradient characteristic for that position. A magneto-optical recording medium recording / reproducing device that suppresses domain wall motion and causes only domain wall motion in the front process. 30 are those which attained improvements in (Fig. 3) side.

  In the second magneto-optical recording medium 20, since the magnetic layer has a four-layer structure, a reproducing magnetic field may not be applied during reproduction.

<Magnetic / magnetic recording medium recording / reproducing method and magneto-optical recording medium recording / reproducing apparatus>
FIG. 3 is a block diagram for explaining a magneto-optical recording medium recording / reproducing method and a magneto-optical recording medium recording / reproducing apparatus according to the present invention,
FIG. 4 shows the temperature gradient in the blue laser beam spot when the first or second magneto-optical recording medium shown in FIG. 1 or 2 is reproduced by the magneto-optical recording medium recording / reproducing method according to the present invention. Schematic diagram shown for explanation by the difference in
FIG. 5 is a diagram comparing the temperature distribution of the red laser beam and the temperature distribution in the tangential direction (track direction) when the rim intensity of the blue laser beam spot is varied.

  As shown in FIG. 3, the magneto-optical recording medium recording / reproducing apparatus 30 according to the present invention reproduces both the first and second magneto-optical recording media 10 and 20 described above with reference to FIGS. It is configured to be possible. The magneto-optical recording media 100 and 200 of the conventional examples 1 and 2 described above with reference to FIGS. 6 and 9 are also applicable.

  In the magneto-optical recording medium recording / reproducing apparatus 30 described above, the turntable 33 is fixed to the shaft of the spindle motor 32 that is rotationally driven by the spindle motor drive circuit 31, and information signals are recorded on the turntable 33 at an extremely high density. The first magneto-optical recording medium 10 or the second magneto-optical recording medium 20 to be reproduced is mounted integrally with the turntable 33 so as to be rotatable at a constant linear velocity (CLV) at, for example, 3.0 m / sec.

  Further, on the upper surface side of the first or second magneto-optical recording medium 10 or 20, a magnetic head 36 connected to a magnetic head drive circuit 35 via a switch 34 for switching between a magnetic field modulation recording signal and a reproducing magnetic field signal. Is provided to be movable in the radial direction (radial direction) of the magneto-optical recording medium 10 or 20.

  Further, on the lower surface side of the first or second magneto-optical recording medium 10 or 20, an optical pickup 40 connected to the laser drive circuit 37 has a magnetic head sandwiching the first or second magneto-optical recording medium 10 or 20. 36 is provided so as to be movable in the radial direction of the first or second magneto-optical recording medium 10 or 20 while always facing the recording medium 36, and the detection output from the pickup 40 is processed by the reproduction signal processing circuit 38. It has become.

  Here, the optical pickup 40 described above includes a blue semiconductor laser 42 that emits a blue laser beam BL having a wavelength of 450 nm or less in the pickup housing 41, and a blue laser beam emitted from the blue semiconductor laser 42 in a divergent light state. The collimator lens 43 that converts BL into parallel light and the two directions perpendicular to the optical axis of the blue semiconductor laser 42 are the radial direction (radial direction) of the first or second magneto-optical recording medium 10 or 20, and this diameter. When defined as a tangential direction (tangential direction, track direction) of the first or second magneto-optical recording medium 10 or 20 substantially orthogonal to the direction, the first or second magneto-optical element is used using a double-sided cylindrical lens or the like. Only the tangential direction of the recording medium 10 or 20 is enlarged and the first or second magneto-optical recording medium 10 or 20 from the objective lens 47 described below is enlarged. The beam shaping element 44 for adjusting the rim intensity of the blue laser beam spot BLS irradiated on the laser beam, the blue laser beam BL passing through the beam shaping element 44 and the reflection from the first or second magneto-optical recording medium 10 or 20 Focus control and tracking control are performed by a polarization beam splitter 45 having a polarizing transflective dielectric multilayer film 45a for separating light and a two-dimensional actuator 46, and a numerical aperture NA is 0.7 or more. At least one surface is formed as an aspherical surface, and the blue laser beam BL transmitted through the transflective dielectric multilayer film 45a of the polarization beam splitter 45 is narrowed down to blue on the first or second magneto-optical recording medium 10 or 20. An objective lens 47 for irradiating the laser beam spot BLS and the first or second magneto-optical recording medium 10 or After the reflected light from 0 is converted through 90 ° by the transflective dielectric multilayer film 45a of the polarizing beam splitter 45 through the objective lens 47, the analyzer 48 and the detection lens 49 for detecting the reflected light and the light detection The container 50 is accommodated.

  When an information signal is recorded while the first or second magneto-optical recording medium 10 or 20 is rotated, a magnetic field modulation recording signal obtained by modulating input data in accordance with a predetermined disk format is used as a switch 34, a magnetic head drive circuit. 35, and the signal surface of the first or second magneto-optical recording medium 10 or 20 is raised by the blue laser beam BL for recording from the blue semiconductor laser 42 in the optical pickup 40. A magnetic field modulation recording signal is recorded on the signal surface of the first or second magneto-optical recording medium 10 or 20 by the magnetic head 36 while being heated. The signal surface of the first or second magneto-optical recording medium 10 or 20 is the first to third magnetic layers 13 to 15 or first to fourth magnetic layers described above with reference to FIG. 1 or FIG. This is equivalent to a generic name of 23-26.

  On the other hand, when reproducing the recorded information signal, the weak laser power from the blue semiconductor laser 42 in the optical pickup 40 by the laser driving circuit 37 with the first or second magneto-optical recording medium 10 or 20 rotated. A blue laser beam BL for reproduction is emitted in this step, and the blue laser beam BL for reproduction is converted into parallel light by a collimator lens 43, and then the beam shaping element 44 uses the first or second magneto-optical recording medium 10 or 20. Only the tangential direction (tangential direction, track direction) is enlarged, passed through the polarization beam splitter 45, and then the reproduction blue laser beam spot BLS narrowed down by the objective lens 47 is used as the first or second magneto-optical recording medium. 10 or 20 is irradiated on the signal surface, and the return light reflected by this signal surface is reflected by the objective lens 47 and the polarization beam. Splitter 45, an analyzer 48, and detected by a photodetector 50 via a detection lens 49, and sent to the reproduced signal processing circuit 38.

  Here, when the blue laser beam spot BLS narrowed down by the objective lens 47 which is the main part of the present invention is irradiated onto the first or second magneto-optical recording medium 10 or 20 during reproduction, the blue laser beam spot BLS The rim strength will be described with reference to FIGS.

  4A to 4C, the blue laser beam spot BLS at the time of reproduction irradiated by the objective lens 47 along the track TR on the signal surface of the first or second magneto-optical recording medium 10 or 20 is irradiated. It shows the state being done.

  At this time, the rim intensity Rim of the blue laser beam spot BLS during reproduction is defined as Rim = intensity in the radial direction of the magneto-optical recording medium / intensity in the tangential direction of the magneto-optical recording medium. In the case of Rim> 1 shown in FIG. 4A, the case of Rim = 1 shown in FIG. 4B, and the case of Rim <1 shown in FIG. These three cases are possible.

  Here, in the case of Rim> 1 shown in FIG. 4A, the isothermal distribution in the blue laser beam spot BLS is more closely spaced in the radial direction of the medium than in the tangential direction of the medium. Therefore, the strength in the radial direction of the medium is larger than the strength in the tangential direction of the medium.

In the case of Rim = 1 shown in FIG. 4B, the isothermal distribution in the blue laser beam spot BLS is approximately the same between the tangential direction of the medium and the radial direction of the medium. Therefore, the strength in the radial direction of the medium is substantially the same as the strength in the tangential direction of the medium.

On the other hand, in the case of Rim <1 shown in FIG. 4C, the isotherm distribution in the blue laser beam spot BLS is opposite to the case of Rim> 1 shown in FIG. Since the interval of the isotherm is closer in the tangential direction of the medium with respect to the direction, the strength in the tangential direction of the medium is larger than the strength in the radial direction of the medium.

  In FIG. 5, 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 / s, and the traveling direction of each beam spot is normal. The tangential position of the beam spot is shown, and the vertical axis shows the temperature (K) of each beam spot.

  In FIG. 5, when the rim intensity Rim of the blue laser beam spot BLS at the time of reproduction is set to 1 (in the case of Rim = 1), as described above with reference to FIG. The temperature gradient characteristic for the position of the blue laser beam spot BLS is considerably steeper than the temperature gradient characteristic for the position of the long wavelength red laser beam spot due to the difference in beam diameter and energy density.

  On the other hand, when the rim intensity Rim of the blue laser beam spot BLS during reproduction is set to be larger than 1 (when Rim> 1), the temperature gradient characteristic of the blue laser beam spot BLS with respect to that position is represented by the red laser beam. It is possible to approximate the temperature gradient characteristic for the position of the spot.

  On the other hand, when the rim intensity Rim of the blue laser beam spot BLS during reproduction is set to be smaller than 1 (when Rim <1), the temperature gradient characteristic of the short wavelength blue laser beam spot BLS with respect to that position is Rim = 1. It becomes steeper than the case.

  In this embodiment, as described above, the tangential direction of the first or second magneto-optical recording medium 10 or 20 by the beam shaping element 44 with respect to the blue laser beam BL from the blue semiconductor laser 42 during reproduction (tangential direction, Since only the rim intensity Rim of the blue laser beam spot BLS at the time of reproduction can be taken as Rim> 1 shown in FIG. 4A, reproduction is performed by setting this rim intensity Rim. The thermal diffusion in the radial direction (radial direction) of the first or second magneto-optical recording medium 10 or 20 is suppressed with respect to the blue laser beam spot BLS at the time, and the blue laser beam spot BLS at the time of reproduction is suppressed. Thus, the temperature gradient in the tangential direction (tangential direction, track direction) of the first or second magneto-optical recording medium 10 or 20 is long wavelength red. Since the temperature gradient characteristic of the laser beam spot approaches and becomes gentle, the domain wall motion in the unnecessary rear process that occurs in the blue laser beam spot BLS when the first or second magneto-optical recording medium 10 or 20 is reproduced. In addition, since only the domain wall motion is suppressed in the front process, it is possible to improve the reproduction performance by a short wavelength laser beam.

1 is a cross-sectional view schematically showing a first magneto-optical recording medium applied to a magneto-optical recording medium recording / reproducing method and a magneto-optical recording medium recording / reproducing apparatus according to the present invention. FIG. 4 is a cross-sectional view schematically showing a second magneto-optical recording medium applied to a magneto-optical recording medium recording / reproducing method and a magneto-optical recording medium recording / reproducing apparatus according to the present invention. FIG. 2 is a configuration diagram for explaining a magneto-optical recording medium recording / reproducing method and a magneto-optical recording medium recording / reproducing apparatus according to the present invention. When reproducing the first or second magneto-optical recording medium shown in FIG. 1 or 2 by the magneto-optical recording medium recording / reproducing method according to the present invention, the temperature gradient in the blue laser beam spot is caused by the difference in rim intensity. It is the schematic diagram shown in order to demonstrate. It is the figure which compared the temperature distribution of the tangential direction (track direction) when changing the rim intensity | strength of a red laser beam and the rim intensity | strength of a blue laser beam spot. 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: First magneto-optical recording medium,
11 ... light transmissive substrate, 12 ... transparent first dielectric layer,
13 to 15: first to third magnetic layers having a three-layer structure;
16 ... second dielectric layer, 17 ... protective layer,
20 ... Second magneto-optical recording medium,
21 ... Light transmissive substrate, 22 ... Transparent first dielectric layer,
23 to 26 ... first to fourth magnetic layers having a four-layer structure,
27 ... second dielectric layer, 28 ... protective layer,
30. Magneto-optical recording medium recording / reproducing apparatus,
31 ... Spindle motor drive circuit, 32 ... Spindle motor, 33 ... Turntable, 34 ... Switch, 35 ... Magnetic head drive circuit, 36 ... Magnetic head,
37 ... Laser drive circuit,
40 ... Optical pickup,
41 ... pickup housing, 42 ... blue semiconductor laser, 43 ... collimator lens,
44 ... Beam shaping element, 45 ... Polarizing beam splitter,
46 ... Two-dimensional actuator, 47 ... Objective lens,
48 ... Analyzer, 49 ... Detection lens, 50 ... Photo detector,
BL ... Blue laser beam, BLS ... Blue laser beam spot,
Rim: Rim intensity of the blue laser beam spot during playback.

Claims (2)

Using a magneto-optical recording medium in which at least three or more magnetic layers having the functions of a domain wall motion layer, an exchange coupling force control layer, and a recording layer are laminated from the side irradiated with a laser beam spot of a short wavelength, After the recording mark corresponding to the information signal is recorded in the perpendicular recording direction in the form of a magnetic domain by the external magnetic field from the magnetic head while irradiating the laser beam spot, the magnetic domain has the exchange coupling force. The exchange coupling force control layer is exchange-coupled to the domain wall motion layer via a control layer and heated by irradiation with the short wavelength laser beam spot while applying a reproduction magnetic field from the magnetic head as necessary during reproduction. Magneto-magnetic recording medium recording reproduction is performed by causing domain wall movement so as to expand the magnetic domain that is exchange-coupled in the domain wall moving layer. In the method,
The rim intensity Rim of the short-wavelength laser beam spot irradiated onto the magneto-optical recording medium at the time of reproduction,
By defining Rim = intensity in the radial direction of the magneto-optical recording medium / intensity in the tangential direction of the magneto-optical recording medium, the rim intensity Rim is set to 1 or more (Rim> 1). A magneto-optical recording medium recording / reproducing method characterized in that a temperature gradient characteristic of a laser beam spot with respect to its position is made closer to a temperature gradient characteristic of a long wavelength laser beam spot with respect to that position. Using a magneto-optical recording medium in which at least three or more magnetic layers having the functions of a domain wall motion layer, an exchange coupling force control layer, and a recording layer are laminated from the side irradiated with a laser beam spot of a short wavelength, After the recording mark corresponding to the information signal is recorded in the perpendicular recording direction in the form of a magnetic domain by the external magnetic field from the magnetic head while irradiating the laser beam spot, the magnetic domain has the exchange coupling force. The exchange coupling force control layer is exchange-coupled to the domain wall motion layer via a control layer and heated by irradiation with the short wavelength laser beam spot while applying a reproduction magnetic field from the magnetic head as necessary during reproduction. Magneto-magnetic recording medium recording reproduction is performed by causing domain wall movement so as to expand the magnetic domain that is exchange-coupled in the domain wall moving layer. In the device,
A semiconductor laser for emitting the short-wavelength laser beam;
A beam shaping element that expands only the tangential direction of the magneto-optical recording medium with respect to the short-wavelength laser beam emitted from the semiconductor laser;
An optical pickup including at least an objective lens that irradiates the magneto-optical recording medium with the short-wavelength laser beam spot obtained by narrowing the short-wavelength laser beam transmitted through the beam shaping element;
The rim intensity Rim of the short-wavelength laser beam spot irradiated onto the magneto-optical recording medium at the time of reproduction,
Rim = diameter intensity of the magneto-optical recording medium / intensity in the tangential direction of the magneto-optical recording medium When the rim intensity Rim is set to 1 or more (Rim> 1) by the beam shaping element, reproduction is performed. A magneto-optical recording medium recording / reproducing apparatus characterized in that the temperature gradient characteristic of the short-wavelength laser beam spot with respect to that position is sometimes close to the temperature gradient characteristic of the long-wavelength laser beam spot with respect to that position.

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