JP2005346784A - Magneto-optical recording medium and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remarkably improve the manufacture yield of media and to mass-produce the media at a low cost by correcting influence on medium characteristics due to the error of a magnetic wall displacement layer. <P>SOLUTION: A magneto-optical recording medium is provided with at least: a substrate; an interference layer for making information reproducing light interfere; the magnetic wall displacement layer where a magnetic wall is displaced contributing to the reproduction of information; a memory layer holding a recording magnetic domain corresponding to the information; and an interruption layer arranged between the magnetic wall displacement layer and the memory layer, and reproduces the information by displacing the magnetic wall of the recording magnetic domain transferred from the memory layer to the displacement layer by the temperature gradient of the medium by irradiation with the information reproducing light and enlarging the recording magnetic domain. This invention is achieved by using the magneto-optical recording medium characterized in that the interference layer is composed of a dielectric material consisting of nitride, the magnetic wall displacement layer is constituted of a plurality of magnetic layers, the film thickness of the layer closest to the interference layer among the plurality of magnetic wall displacement layers is ≤20 nm, and the nitrogen content of at least one part on the magnetic wall displacement side of the interference layer is different. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a magneto-optical recording medium that records and reproduces information with a laser beam using a magneto-optical effect.

  In recent years, as a rewritable high-density recording method, a magneto-optical recording medium and a recording / reproducing apparatus for recording information by writing magnetic domains in a magnetic thin film using the thermal energy of a semiconductor laser and reading the recorded information using a magneto-optic effect Is attracting attention. Recently, the data handled has been diversified into various information such as voice, images, and moving images, and the required data size has continued to increase. Therefore, the recording density of this magneto-optical recording medium has been increased to achieve higher capacity recording. There is an increasing demand for media.

  Using a magnetic field modulation method that modulates an external magnetic field while irradiating a high-power laser onto a magneto-optical recording medium, a magnetic domain smaller than the light spot can be recorded by sufficiently increasing the switching speed of the magnetic field modulation. .

  On the other hand, the reproduction depends on the beam waist diameter determined by the laser wavelength λ of the reproduction optical system and the numerical aperture NA of the objective lens, so that the limit of the spatial frequency of the record pits capable of reproducing the signal is about 2 NA / λ. turn into.

  Therefore, in order to realize high density in the conventional optical disc, it is necessary to shorten the laser wavelength of the reproducing optical system or increase the numerical aperture of the objective lens.

  However, when reproduction is performed using a blue-violet laser having a wavelength of about 350 nm to 450 nm as laser light, the spot diameter is reduced to ½ or less compared to conventional red laser light, and as a result, a certain laser required for reproduction is obtained. When power is used, the beam intensity at the center of the spot of the reproduction laser beam becomes extremely high, and the intensity of the center portion of the reproduction laser beam spot on the magneto-optical recording medium becomes extremely high, which may cause a significant increase in temperature. . As a result, if the temperature rise during magneto-optical recording / reproduction is significant, the signal level (carrier level) of the reproduction signal will be small, and it will be easily affected by system noise and medium noise in the reproduction system, and the reproduction characteristics will be improved. It will get worse.

  On the other hand, when the numerical aperture of the objective lens is increased, the distance between the disk serving as the recording medium and the objective lens is narrowed, so that the risk of collision increases. In addition, since the influence of tilt due to disc surface wobbling becomes large, there arises a problem that a tilt servo of the pickup becomes necessary and a demand for mechanical accuracy becomes severe.

  On the other hand, a so-called magnetic super-resolution technique for improving the recording density by devising the configuration of the recording medium and the reproducing method has been developed. For example, Japanese Patent Laid-Open No. 7-334877 discloses a memory layer that holds recorded information, a reproducing layer that masks a part of the reproducing spot and contributes to reproduction by a light spot, and controls their exchange coupling force. The barrier layer 2 is laminated. Due to the temperature distribution generated by irradiating the reproduction light spot to the reproduction layer irradiated with the reproduction light spot, the recording information of the recording layer is transferred only to a portion above the threshold temperature in the reproduction spot, A portion below a certain threshold temperature becomes an in-plane magnetic layer that does not contribute to information reproduction. As a result, recorded information equal to or smaller than the spot diameter recorded on the recording layer is transferred only to a portion of the reproduction spot that is equal to or higher than a certain threshold temperature, and the recorded information smaller than the reproduction spot diameter is read by reading the transferred information. Is.

  However, the super-resolution method can reproduce information smaller than the reproduction light spot diameter, but uses the temperature distribution of the reproduction light spot and reads the recorded information from only a part of the reflected light of the reproduction light spot. The level of the playback signal becomes small. Further, in order to further reduce the size of the recorded information in order to improve the recording density, it is necessary to further reduce the aperture in the spot, resulting in a problem that the S / N ratio of the reproduction signal becomes small.

Further, in JP-A-6-290495, a domain wall moving layer having a small domain wall coercive force is provided on the incident side of the reproduction light, and the domain wall of the domain wall moving layer is moved to the high temperature side using the temperature gradient in the reproduction spot, A method for enlarging and reproducing magnetic domains within a spot is disclosed. According to this, even if the recording mark size is reduced, the signal is reproduced while enlarging the magnetic domain, so that the reproduction light can be used effectively and the resolution can be increased without reducing the signal amplitude.
Japanese Patent Laid-Open No. 7-334877 Japanese Patent Laid-Open No. 6-290498

  The reproducing method using domain wall motion disclosed in Japanese Patent Application Laid-Open No. 6-290495 is a method having an excellent linear recording density among the super-resolution methods. In other words, if the amount of domain wall movement is always constant, a constant reproduction signal amplitude can be obtained regardless of the size of the recording magnetic domain. However, in order to move the domain wall smoothly in the reproduction spot, it is necessary to control the magnetostatic force in addition to the temperature gradient, and in order to suppress the magnetostatic force when manufacturing the medium, Accurate composition adjustment was essential.

  On the other hand, when mass-producing magneto-optical recording media, it is said that the manufacturing equipment is simplified and the tact time (required time for machine operations, especially the time required for an automatic machine to complete one unit of work) is shortened. It is important to be able to manufacture using an alloy target for cost reduction.

  However, in general, there is a limit to the composition accuracy of the alloy target. For example, in the case of a GdFeCo alloy, an error of about ± 0.5 atomic% as the Gd content occurs, which affects the medium characteristics, resulting in a decrease in the yield of the medium. There was a case.

  The present invention has been made to solve the above-mentioned problems, and by correcting the composition variation of the alloy target by a simple method, the production yield of the medium can be greatly improved, and mass production of the medium can be performed at low cost. The purpose is to do.

  The present invention includes a substrate, an interference layer that interferes with information reproduction light, a domain wall motion layer that contributes to information reproduction and moves a domain wall, a memory layer that retains a recording domain according to information, and the domain wall motion layer The recording magnetic domain is enlarged by moving the domain wall of the recording magnetic domain transferred from the memory layer to the moving layer by a temperature gradient of the medium due to irradiation of information reproducing light. In the magneto-optical recording medium that reproduces the information, the interference layer is made of a dielectric material made of nitride, the domain wall motion layer is composed of a plurality of magnetic layers, and among the plurality of domain wall motion layers, This is achieved by using a magneto-optical recording medium, wherein the thickness of the layer closest to the interference layer is 20 nm or less, and the nitrogen content of at least a part of the interference layer on the domain wall motion layer side is different. It is.

  As described in detail above, by using the magneto-optical recording medium manufacturing method according to the present invention, a high-density magneto-optical recording medium can be manufactured at low cost.

  As the domain wall motion layer, two or three magnetic layers are stacked and the saturation magnetization cancels each other, so that the net saturation magnetization from the Curie temperature Ts of the blocking layer to the Curie temperature Tc of the domain wall motion layer is substantially zero. The characteristics can be improved.

  In order to manufacture a domain wall moving medium with a simple manufacturing apparatus and high throughput, it is desirable to prepare and form an alloy target according to the film formulation of each layer at this time. In this case, the deposited film also reflects the composition of the target, so that it is affected by the composition accuracy of the target.

  The present inventor has noticed that the characteristics of the magnetic film change when the dielectric material film made of nitride and the magnetic film come into contact with each other, and has found a method for improving manufacturing stability by utilizing this property. That is, the rare earth-transition metal alloy has a phenomenon in which the rare earth metal is nitrided at a portion in contact with the dielectric material made of nitride, and apparently becomes rich in transition metal and the compensation temperature is lowered. Therefore, the domain wall motion layer has a laminated structure, and the influence of the composition deviation has the greatest effect on the characteristics. By increasing the nitrogen content at the interface and reducing the nitrogen content at the interface in the case of rich transition metals, a medium capable of stable signal reproduction without being affected by stray magnetic fields or external magnetic fields from the memory layer, It was possible to manufacture with a high yield.

  Since the adjustment of the compensation temperature becomes difficult as the thickness of the first domain wall motion layer closest to the interference layer increases, the thickness of the first domain wall motion layer is preferably 20 nm or less.

  In addition, although the case where the domain wall motion layer has a laminated structure has been described, it goes without saying that the same effect can be obtained even when the domain wall motion layer is a single layer.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 5A shows a cross-sectional view of the optical disc in the present embodiment. In the optical disk shown in FIG. 5, an interference layer 102, a domain wall motion layer 1, a blocking layer 2, a memory layer 3, and a protective layer 103 are laminated on a substrate 101 in this order. The domain wall motion layer 1 is formed by laminating a plurality of magnetic layers in order to stabilize signal reproduction.

  An arrow 11 in each magnetic material in FIG. 5A indicates the direction of transition metal sublattice magnetization of the recording magnetic domain held in the film, and a Bloch domain wall 12 exists in a portion where the adjacent magnetizations are not parallel. To do. The substrate 101 is usually made of a transparent material such as glass or polycarbonate. Each of these layers can be deposited by continuous sputtering using a magnetron sputtering apparatus or continuous vapor deposition.

The interference layer 102 is provided to enhance the magneto-optical effect, and it is preferable to use a dielectric material made of a transparent nitride such as Si ₃ N ₄ or AlN. The protective layer 103 is used for protecting the magnetic layer, and the same material as the interference layer 102 is used. In addition, in order to optimize the thermal structure of the entire medium, a metal layer made of Al, AlTa, AlTi, AlCr, AlSi, Cu, or the like may be further provided on the protective layer 103. Since the protective layer 103 and the metal layer provided as necessary are irrelevant to the essence of the present invention, detailed description thereof is omitted here.

  The memory layer 3 is made of a material having a large perpendicular magnetic anisotropy such as a rare earth-iron group element amorphous alloy, for example, TbFeCo, DyFeCo, TbDyFeCo, which can stably store minute recording pits. The magnetic domain of the layer is held up or down. In addition, a configuration in which information can be magnetically transferred to another layer using a perpendicular magnetization film such as garnet, Pt / Co, Pd / Co, or the like may be used.

  The blocking layer 2 is a rare earth-iron group amorphous alloy such as GdCo, GdFeCo, GdFe, GdFeCoAl, DyFeCoAl, TbFe, TbFeCo, TbFeCoAl, TbDyFeCoAl, TbFeAl, and has a Curie temperature set lower than the other layers. .

  The domain wall motion layer 1 is preferably a rare earth-iron group amorphous alloy having a small perpendicular magnetic anisotropy, such as GdCo, GdFeCo, GdFe, NdGdFeCo.

  The relationship between the Curie temperatures of these layers satisfies the relationship of Tc1, Tc3> Tc2, where the Curie temperature of the domain wall motion layer 1 is Tc1, the Curie temperature of the blocking layer 2 is Tc2, and the Curie temperature of the memory layer 3 is Tc3. The magnetic domains recorded in the memory layer 3 by exchange coupling at room temperature are transferred to the blocking layer 2 and the domain wall motion layer 1.

  The thickness of each layer is 20 to 100 nm for the interference layer 102, 20 to 40 nm for the domain wall motion layer 1, 7 to 20 nm for the blocking layer 2, 40 to 100 nm for the memory layer 3, and 40 to 80 nm for the protective layer 103.

  Further, a protective coat made of a polymer resin may be further added to this configuration. Alternatively, the substrate 101 after film formation may be bonded. Further, the order of lamination may be reversed, and the light incident direction during recording / reproduction may be opposite to the substrate.

  Recording of a data signal onto the optical disk of the present invention is performed by modulating an external magnetic field while irradiating a laser beam having a power such that the temperature of the memory layer 3 becomes a temperature near the Curie temperature Tc3 while moving the medium. In this case, if the modulation frequency of the external magnetic field is increased, a recording magnetic domain smaller than the light spot diameter can be formed, and as a result, a signal can be recorded with a period less than the diffraction limit of light.

  FIG. 5B shows the temperature distribution at the track center when the optical disk is moved to the right while irradiating the optical disk with laser light. As shown in this temperature profile, the position where the film temperature becomes maximum is slightly behind the center of the laser spot, although it depends on the linear velocity of the disk.

FIG. 5C is a diagram showing the distribution of the domain wall energy density σ ₁ in the domain wall moving layer 1. Thus, the domain wall energy density σ ₁ decreases as the temperature rises. Therefore, if there is a temperature gradient in the moving direction of the optical disk, the domain wall energy density σ ₁ decreases toward the maximum temperature position. Then, a force F ₁ that can be expressed by F ₁ = dσ ₁ / dx acts on the domain wall of the domain wall moving layer existing at the position x.

The force F ₁ acts to move the domain wall toward the lower domain wall energy, and the domain wall moving layer 1 has a small domain wall coercive force and a large domain wall mobility, so that the domain wall is easily moved by this force F ₁ alone. .

  In FIG. 5A, each magnetic layer is a perpendicular magnetization film before the reproduction laser beam is irradiated on the disk, that is, at room temperature, and the magnetic domains recorded in the memory layer 3 are domain walls through the blocking layer 2. The magnetic domain is transferred by exchange coupling with the moving layer 1. At this time, a domain wall 12 exists between the magnetic domains 11 opposite to each other indicated by arrows in each layer.

When the film temperature rises and the blocking layer 2 becomes equal to or higher than the Curie temperature Tc2, the exchange coupling between the memory layer 3 and the blocking layer 2 is lost, and the domain wall moving layer 1 having a small domain wall coercive force cannot hold a magnetic domain, resulting in a temperature gradient. The domain wall moves to the high temperature side in accordance with the force F ₁ applied by. At this time, the moving speed of the domain wall is sufficiently higher than the moving speed of the disk, so that a magnetic domain larger than the magnetic domain recorded in the memory layer 3 is obtained in the laser spot.

  At the time of recording, the irradiation laser beam is set to a higher power than at the time of reproduction, the medium is heated to a temperature higher than the Curie temperature Tc3 of the memory layer 3, and a recording magnetic field (not shown) modulated according to the recording data is used. Applied to at least the memory layer 3. Thereby, a recording magnetic domain corresponding to the recording data can be recorded in the memory layer 3 of the medium.

  In general, the film characteristics of the blocking layer 2 and the memory layer 3 can be considered as follows.

  If the Curie temperature of the blocking layer 2 is too low, transfer of the recording magnetic domain from the memory layer to the domain wall motion layer at room temperature tends to be incomplete. Further, since the position at which the domain wall motion starts becomes unstable because the temperature gradient is gentle, it is preferable to set the temperature between 100 ° C. and 200 ° C., and provide a temperature difference from room temperature to some extent. Furthermore, in order to reduce the stray magnetic field from the blocking layer 2, it is preferable to select a composition in which the compensation temperature is close to the Curie temperature.

  The memory layer preferably has a large Curie temperature difference from the blocking layer 2 because the recording magnetic domain does not deteriorate even when the temperature rises during reproduction. Specifically, the Curie temperature is preferably around 300 ° C. In order to perform stable recording, the saturation magnetization near the Curie temperature is increased to some extent, and the compensation temperature of the memory layer is between room temperature and the Curie temperature of the blocking layer 2 in order to reduce the stray magnetic field at the reproduction temperature as much as possible. It is preferable to set to. For example, when the compensation temperature is close to room temperature, the saturation magnetization of the memory layer at the reproduction temperature reaches about 100 emu / cc, and the stray magnetic field from the memory layer prevents the movement of the domain wall 12 in the domain wall moving layer 1. There is.

  When the blocking layer 2 reaches the Curie temperature, the domain wall moving layer 1 generates a force that moves the domain wall to the high temperature side according to the temperature gradient, while the saturation magnetization of the domain wall moving layer itself and the magnitude of the magnetic field generated from the surroundings (memory layer, etc.). The static magnetic force according to the thickness works. This static magnetic force is in the direction of assisting or preventing the movement of the domain wall depending on the direction of magnetization, and is preferably as small as possible for stable information reproduction. That is, the saturation magnetization of the domain wall motion layer is desirably small in a wide temperature range equal to or higher than the Curie temperature of the blocking layer 2.

In this example, the nitrogen partial pressure was changed subsequent to the formation of the interference layer 102 to form the composition adjustment layer 4, but the nitrogen content was changed by plasma treatment of the surface of the interference layer 102. Needless to say, the same effect can be obtained by setting the nitrogen content of the interference layer 102 to a desired nitrogen content, or by changing the nitrogen partial pressure during the formation of the interference layer 102. .
<Experimental example 1>
After attaching B-doped Si and GdFeCo and TbFeCo targets according to the composition of each magnetic layer to a DC magnetron sputtering apparatus and fixing a polycarbonate substrate on which tracking guide grooves are formed to a substrate holder, 1 × While evacuating the chamber with a cryopump until a high vacuum of 10 ⁻⁵ Pa or less, Ar gas was introduced into the chamber until the pressure reached 0.5 Pa, and each target was sputtered while rotating the substrate. Was deposited.

  First, a 35 nm SiN layer was formed as the interference layer 102. At this time, nitrogen gas was introduced in addition to Ar gas, and a film was formed by direct current reactive sputtering. After the formation of the interference layer 102, only the nitrogen partial pressure was adjusted by a film formation method almost the same as that of the interference layer 102 to obtain a composition adjustment layer 4 having a thickness of 5 nm. Subsequently, the first domain wall motion layer 11 is a GdFeCo layer having a thickness of 20 nm, the second domain wall motion layer 12 is a GdFeCr layer having a thickness of 20 nm, the blocking layer 2 is a TbFe layer having a thickness of 10 nm, and the memory layer is a TbFeCo layer. Films were sequentially formed to a thickness of 60 nm. Finally, a 50 nm SiN layer was formed as a protective layer.

Each magnetic layer was formed using an alloy target prepared according to a pre-designed film formulation. The domain wall motion layer 1 has a two-layer configuration including a first domain wall motion layer 11 and a second domain wall motion layer 12, and the side close to the interference layer 102 is the first domain wall motion layer 11. The film thicknesses of the first domain wall motion layer 11 and the second domain wall motion layer 12 are 20 nm, and the design values of the Curie temperature Tc11 of the first domain wall motion layer 11 and the Curie temperature Tc12 of the second domain wall motion layer 12 are respectively The Curie temperatures were 290 ° C. and 210 ° C., and the compensation temperatures were 280 ° C. and 50 ° C. The design compositions at this time were Gd _0.27 Fe _0.63 Co _0.1 and Gd _0.18 Fe _0.73 Cr _0.09 , respectively.

  The target was selected so that the blocking layer 2 had a Curie temperature Tc2 of 150 ° C., and the memory layer had a Curie temperature Tc3 of 320 ° C. and a compensation temperature of about 140 ° C.

  FIG. 2 shows an example in which the first domain wall motion layer 11 close to the interference layer 102 has an error of a maximum of 0.5 atomic% as a composition shift of the alloy target. FIG. 2 (1) shows a case where the target according to the design center is obtained. In this case, the Curie temperature and the compensation temperature are obtained according to the design value even if nothing is done. Next, in the case of FIG. 2 (2), the target composition is richer in the rare earth than the design value. In this case, when the composition adjustment layer 4 is formed, the interface between the interference layer 102 and the domain wall motion layer is enriched with nitrogen by increasing the nitrogen partial pressure by a factor of 2 to partially nitride Gd of the domain wall motion layer. Compared to the case without compensation, the Curie temperature and compensation temperature of the domain wall motion layer can be brought closer to the design values. On the other hand, when the target is richer in the transition metal than the design value as shown in FIG. 2 (3), the Curie temperature of the domain wall motion layer is reduced by reducing the nitrogen partial pressure at the time of forming the composition adjustment layer 4 to 1/2. The compensation temperature was close to the design value.

  The nitrogen partial pressure can be changed at any time by changing the target of the sputtering apparatus or by changing the composition of the domain wall motion layer due to consumption of the target in use. It goes without saying that the composition change of the domain wall motion layer due to the consumption of the target in use can be performed by process management in a normal production line, for example, by periodically monitoring the composition of the domain wall motion layer.

While rotating these discs at a linear velocity of 2.4 m / s, using a laser beam with a wavelength of 650 nm, an objective lens with NA of 0.60 and an external magnetic field of 250 oE, information is recorded by (1-7) modulation, and then reproduced. As a result, all the three discs had a bit error rate of 1 × 10 ⁻⁴ at a recording density of 0.075 μm / bit.

  Further, in this experimental example, in order to smoothly move the domain wall, the information tracks were annealed with a high-power laser before information recording / reproduction so that the domain wall was not generated on the side of the track.

The laser for annealing treatment may be irradiated from either the front side of the substrate (film formation side) or the back side of the substrate (opposite side of the film formation side). Irradiation can be performed preferably because the laser spot for annealing can be narrowed down.
<Experimental example 2>
Next, an experiment was conducted in the case where the domain wall motion layer has a three-layer structure. Conditions other than the domain wall motion layer are the same as in Experimental Example 1.

In the present experimental example, the domain wall motion layer has a three-layer structure of 14 nm each, and the first domain wall motion layer 11, the second domain wall motion layer 12, and the third domain wall motion layer 13 from the side closer to the interference layer 102, The film was designed so that the Curie temperatures Tc11, Tc12, and Tc13 were 310 ° C, 270 ° C, 230 ° C, and the compensation temperatures were 290 ° C, 260 ° C, 60 ° C. The design compositions at this time were Gd _0.3 Fe _0.58 Co _0.12 , Gd _0.26 Fe _0.69 Co _0.05 and Gd _0.21 Fe _0.74 Cr _0.05 , respectively.

FIG. 3 shows a case where an error occurs in the target composition of the first domain wall motion layer. Also in this case, as in Example 1, composition deviation of the domain wall motion layer was compensated by adjusting the nitrogen partial pressure in the composition adjustment layer 4, and information was recorded and reproduced under the same conditions as in Example 3. Stable information recording and playback were possible with both discs. In the case of this experimental example, since the film thickness of the first domain wall motion layer is thinner than in Experimental Example 1, the compensation effect by the composition adjustment layer 4 is high, and the Curie temperature and the compensation temperature are almost the same as the design values. Yes.
<Experimental example 3>
A laminated film similar to that of Experimental Example 1 was formed on a stepped substrate on which lands / grooves were formed. Since the step is magnetically separated at the track side at the same time as the film formation, the annealing process using the high-power laser performed in Experimental Example 1 was omitted.

  FIG. 4 shows a cross-sectional view of the optical disk of this experimental example, in which a rectangular guide groove having a depth of 160 nm is formed on the substrate 101. A film was formed on this substrate with the same film formulation as in Experimental Example 1. Exactly, some film is deposited on the taper portion, but the film thickness is much thinner than that of the land / groove portion, so that the magnetic coupling at the step portion can be ignored.

When a film was formed on this disk under the same conditions as in Experimental Example 1 and information was recorded and reproduced, a reproduction signal equivalent to that in Experimental Example 1 was obtained, and by performing land / groove recording, a track pitch direction was obtained. The recording density could also be improved.
<Experimental example 4>
Next, the same substrate and film configuration experiment as in Experimental Example 1 was conducted except that the thickness of the second domain wall motion layer 12 was 15 nm, the compensation temperature was 0 ° C., and the Curie temperature was 220 ° C. In the case of this experiment, since the second domain wall motion layer 12 is thinner than Experimental Example 1, the Curie temperature and the compensation temperature were adjusted to cancel the magnetization with the first domain wall motion layer. At this time, since the first domain wall motion layer 11 is not changed from Experimental Example 1, the nitrogen content of the composition adjustment layer 4 is changed in the same manner as in Experimental Example 1 with respect to the composition shift of the first domain wall motion layer. Thus, the same effect as in Experimental Example 1 could be obtained.

<Comparative Example 1>
For the same recording medium as in Experimental Example 1, a medium was prepared without adjusting the nitrogen content in the composition adjustment layer 4, and a recording / reproducing experiment was performed. When the medium is created at the Curie temperature and the compensation temperature as shown as “no compensation” for each target in FIG. 2, under the same recording / reproducing conditions as in Experimental Example 1, 6 × 10 ⁻⁴ in FIG. In FIG. 2 (3), the error rate deteriorated to 8 × 10 ⁻⁴ .
<Comparative example 2>
Next, for the same recording medium as in Experimental Example 2, a medium was prepared without adjusting the nitrogen content in the composition adjustment layer 4, and a recording / reproducing experiment was performed. When the medium is created at the Curie temperature and the compensation temperature as shown as “no compensation” for each target in FIG. 3, under the same recording / reproducing conditions as in Experimental Example 1, 6 × 10 ⁻⁴ in FIG. In FIG. 3 (3), the error rate deteriorated to 7 × 10 ⁻⁴ .
<Comparative Example 3>
Next, an experiment was performed in the case where the domain wall motion layer has a two-layer structure and the film thickness balance is changed. Conditions other than the domain wall motion layer are the same as in Experimental Example 1.

In this experimental example, the first domain wall motion layer has a two-layer structure of 25 nm and the second domain wall motion layer has a thickness of 15 nm. The design composition at this time was Gd _0.27 Fe _0.63 Co _0.1 and Gd _0.18 Fe _0.73 Cr _0.12 , respectively, and an error rate of 1 × 10 ⁻⁴ was obtained when the target as designed was used. However, when a composition shift occurs in the target, the characteristics of the first domain wall motion layer cannot be compensated even if the nitrogen content of the composition adjustment layer 4 is changed as shown in FIG. 6, and in FIG. ^-4 and FIG. 3 (3), the error rate deteriorated to 6 × 10 ⁻⁴ .

The figure showing the medium structure of one Example of this invention The figure explaining the result of the 1st experiment example of this invention The figure explaining the result of the 2nd experiment example of this invention The figure explaining the board | substrate used in the 4th experiment example of this invention Principle explanatory diagram of the present invention The figure explaining the result of the comparative example of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Domain wall moving layer 2 Blocking layer 3 Memory layer 4 Composition adjustment layer 101 Substrate 102 Interference layer 103 Protective layer

Claims (2)

A substrate, an interference layer that interferes with information reproducing light, a domain wall moving layer that contributes to information reproduction and moves a domain wall, a memory layer that holds a recording magnetic domain according to information, and the domain wall moving layer and the memory layer The recording magnetic domain is expanded by moving the domain wall of the recording magnetic domain transferred from the memory layer to the moving layer according to the temperature gradient of the medium due to the irradiation of the information reproducing light. In a magneto-optical recording medium for reproducing information,
The interference layer is made of metal nitride;
The domain wall motion layer is composed of a plurality of magnetic layers;
Of the plurality of domain wall motion layers, the thickness of the layer closest to the interference layer is 20 nm or less,
A magneto-optical recording medium, wherein the nitrogen content of at least a part of the interference layer on the domain wall motion layer side is different. A substrate, an interference layer that interferes with information reproducing light, a domain wall moving layer that contributes to information reproduction and moves a domain wall, a memory layer that holds a recording magnetic domain according to information, and the domain wall moving layer and the memory layer The recording magnetic domain is expanded by moving the domain wall of the recording magnetic domain transferred from the memory layer to the moving layer according to the temperature gradient of the medium due to the irradiation of the information reproducing light. In a method of manufacturing a magneto-optical recording medium for reproducing information,
The interference layer is made of metal nitride;
The domain wall motion layer is composed of a plurality of magnetic layers;
Of the plurality of domain wall motion layers, the thickness of the layer closest to the interference layer is 20 nm or less,
A method of manufacturing a magneto-optical recording medium, wherein the nitrogen content of at least a part of the interference layer on the domain wall motion layer side is changed.

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