JPWO2004068485A1 - Magneto-optical recording medium and manufacturing method thereof - Google Patents

Abstract

The magneto-optical recording medium (X1) includes a base material (S) having optical transparency, a magnetic part (11) responsible for a recording function and a reproducing function, and a base material (S) and a magnetic part (11). An auxiliary layer (12) having light transmission and having a column structure (12a) in contact with the magnetic part (11) to increase the perpendicular magnetic anisotropy of the magnetic part (11); Is provided.

Description

  The present invention relates to a back-illuminated magneto-optical recording medium and a manufacturing method thereof.

In recent years, magneto-optical recording media have attracted attention. The magneto-optical recording medium is a rewritable recording medium that is configured using various magnetic properties of a magnetic material and has two functions of thermomagnetic recording and reproduction using a magneto-optical effect. The magneto-optical recording medium has a recording layer made of a perpendicular magnetization film, and a predetermined signal is recorded in the recording layer as a change in the magnetization direction. This recording signal is read by a predetermined optical system for reading a reproduction signal. Such a magneto-optical recording medium is disclosed in, for example, Japanese Patent Application Laid-Open Nos. 6-111405 and 6-290496.
In the field of magneto-optical recording media, various reproducing systems have been developed for practically reproducing signals recorded at a high density exceeding the limit of resolution in an optical system for reading reproduced signals. For example, MSR (Magnetic Super Resolution), MAMMOS (Magnetic Amplifying Magneto-Optical System), and DWDD (Domain Wall Displacement Detection).
In a DWDD type magneto-optical recording medium, a magnetic material portion having a laminated structure of a recording layer, a reproducing layer, and an intermediate layer therebetween is provided on a predetermined substrate. Each of these three layers is a perpendicular magnetization film generally made of a rare earth-transition metal amorphous alloy, and is laminated so that exchange interaction works between two adjacent layers when not heated. The recording layer exhibits a relatively large domain wall coercivity, the reproducing layer exhibits a relatively small domain wall coercivity, and the intermediate layer has a lower Curie temperature than the other two layers.
A predetermined signal is recorded on the recording layer along the scanning direction of the medium. Specifically, the recording layer is formed with a plurality of magnetic domains each having a predetermined length corresponding to a recording signal, the magnetization of which is alternately reversed continuously in the medium scanning direction. A plurality of domain walls standing at intervals corresponding to the recording signal are formed along the. In the reproducing layer and the intermediate layer, the recording layer and the reproducing layer are exchange-coupled via the intermediate layer under a temperature condition where the medium temperature is lower than the Curie temperature of the intermediate layer, and the medium temperature exceeds the Curie temperature of the intermediate layer. Under a predetermined temperature condition, the domain wall motion phenomenon occurs in the reproducing layer. Under a temperature condition where the medium temperature is lower than the Curie temperature of the intermediate layer, the reproducing layer exchange-coupled to the recording layer via the intermediate layer includes a magnetic domain magnetized in the same direction as the recording layer and a domain wall in the magnetic domain. And are fixed. Under a temperature condition in which the medium temperature is higher than the Curie temperature of the intermediate layer, the spontaneous magnetization of the intermediate layer disappears, and the exchange coupling between the recording layer and the reproducing layer via the intermediate layer is broken. As a result, the domain wall can move in the reproducing layer having a small domain wall coercive force. The domain wall moves to a higher temperature region when a temperature gradient exists in the reproducing layer.
In the reproducing operation of the DWDD type magneto-optical disk in which the information track made of the magnetic material portion having the above-described configuration is formed, the information track is irradiated with a reproducing laser beam while rotating the disk. Scan the information track. At this time, a temperature gradient is generated in the scanning direction in the beam irradiation region inside the information track made of the magnetic material portion. In the beam irradiation region, the magnetic wall moves to the higher temperature side in the reproducing layer at the moment when the magnetic wall of the reproducing layer passes the isothermal line of the Curie temperature in the beam irradiation region from the low temperature region to the high temperature region with the scanning. To do. When the domain wall moves in the reproducing layer in this way, the magnetization of the domain wall moving region is reversed. By detecting this magnetization reversal with a predetermined optical system as a change in the polarization plane of the reflected light, the domain wall motion is detected. By irradiating the reproducing laser beam along the information track and sequentially detecting the domain wall movement, the recording signal of the medium is read.
In reproduction based on such a DWDD system, not the entire spot of the reproduction laser beam, but the isotherm in the beam spot (the isotherm of the Curie temperature of the intermediate layer) of the reproduction layer or the recording layer constituting the information track. Record patterns are discriminated. Therefore, in the DWDD system, even a signal recorded at a high density on the recording layer exceeding the resolution limit in the optical system for reading the reproduction signal, that is, with a recording pattern in which the minimum recording mark length is smaller than the spot diameter. Even if it exists, it can be played back. For example, even when a red laser (beam spot diameter: about 1 μm) is adopted as a reproducing laser beam, a recording mark having a length of 0.1 μm or less can be reproduced.
In the magneto-optical recording medium, the recording density increases as the length of the stable recording mark formed in the recording layer decreases. In the above-described MSR, MAMMOS, and DWDD magneto-optical recording media, there is a particularly strong demand for a high recording density of the recording layer in order to fully exhibit these reproduction resolutions. For example, a recording layer capable of stably recording continuous recording marks having a length of 0.1 μm or less is desired.
In order to form such a minute recording mark, it is necessary to refine the structure of the recording layer. That is, in the recording layer, it is necessary to obtain a magnetic state in which minute magnetic domains can be stably formed by increasing the perpendicular magnetic anisotropy.
In the technical field of magnetic materials, it is known that the magnetic state or magnetic properties of a magnetic film can be influenced by the underlying film on which the magnetic film is formed. Therefore, for example, in a magnetic recording medium that does not involve light irradiation during recording and reproduction, underlayers made of various materials are employed in order to adjust the magnetic state of the recording layer (magnetic film) as desired.
However, in the conventional back-illuminated conventional magneto-optical recording medium with light irradiation from the substrate side at the time of recording and reproduction, the conventional underlayer used in the magnetic recording medium is replaced with the perpendicular magnetic anisotropy of the recording layer. It is not realistic to adopt for improvement. In the magneto-optical recording medium, the recording and reproducing light (laser) needs to be sufficiently transmitted between the substrate and the magnetic material portion including the recording layer. This is because the conventional base film does not have sufficient light transmission.

The present invention has been conceived under such circumstances, and an object thereof is to achieve a high recording density in a back-illuminated magneto-optical recording medium.
According to a first aspect of the present invention, a magneto-optical recording medium is provided. This magneto-optical recording medium has a light-transmitting base material, a magnetic part responsible for a recording function and a reproducing function, and has a light-transmitting property interposed between the base material and the magnetic part. And an auxiliary layer having a column structure surface for increasing the perpendicular magnetic anisotropy of the magnetic part. “Being light transmissive” means sufficiently transmitting the recording laser and reproducing laser irradiated to the magnetic part of the magneto-optical recording medium.
According to such a configuration, a high recording density can be achieved in a back-illuminated magneto-optical recording medium. The magnetic part in the first aspect of the present invention has a recording function and a reproducing function, and therefore includes at least a recording layer. The auxiliary layer is interposed between such a magnetic part and the base material and has a surface in contact with the magnetic part. That is, in the magneto-optical recording medium of the present invention in which each layer is sequentially formed by depositing a material from the substrate side, the magnetic part is formed using the auxiliary layer as a base film. In the present invention, the contact surface of the auxiliary layer with the magnetic part has a column structure including a plurality of thin columns, and the magnetic part is formed by depositing a predetermined magnetic material on the column structure. . By depositing and growing a magnetic material using a thin column on the surface of the auxiliary layer as a nucleus, that is, a base point, a high perpendicular magnetic anisotropy can be obtained in the magnetic portion to be formed, and in the recording layer included therein. The higher the perpendicular magnetic anisotropy of the recording layer, the more stable recording marks can be formed in the recording layer, and as a result, it is suitable for improving the recording density of the recording layer.
The auxiliary layer is light transmissive with respect to the recording laser and the reproducing laser. Therefore, the presence of the auxiliary layer does not hinder the recording process and reproduction of the magneto-optical recording medium.
As described above, in the magneto-optical recording medium according to the first aspect of the present invention, the auxiliary layer provided as the base film of the magnetic part including the recording layer increases the perpendicular magnetic anisotropy of the magnetic part and thus the recording layer. The column structure is provided at the interface with the magnetic part and has sufficient light transmittance. Therefore, according to the magneto-optical recording medium according to the first aspect, it is possible to appropriately achieve a high recording density.
In the first aspect of the present invention, preferably, the column structure surface has a plurality of columns, and the average diameter of the plurality of columns is 5 to 35 nm. In this case, the column structure surface preferably has an average surface roughness Ra of 0.6 nm or less. According to such a fine column structure, the perpendicular magnetic anisotropy of the magnetic part, that is, the recording layer can be appropriately ensured.
Preferably, the auxiliary layer is made of a metal oxide. In this case, preferably, the metal oxide is an oxide of a metal selected from the group consisting of Ag, Al, Ni, Ti, Zr, Y, and Ru, or Ag, Al, Ni, Ti, Zr, Y And an oxide of an alloy containing a metal selected from the group consisting of Ru. The auxiliary layer of the present invention can be appropriately formed from such metal oxides.
Preferably, the auxiliary layer has a thickness of 0.2-5 nm. From the viewpoint of sufficiently growing the column structure at the contact surface of the auxiliary layer with the magnetic part when forming the auxiliary layer by sputtering or the like, and ensuring the light transmittance of the auxiliary layer, the thickness of the auxiliary layer is Such a range is preferable.
Preferably, the auxiliary layer is composed of two or more metal oxide films. In this case, it is preferable that two adjacent metal oxide films have different chemical compositions. By stacking metal oxide films, it may be possible to grow each column on the column structure surface of the auxiliary layer to be elongated.
Preferably, the magnetic part has a multilayer structure including a recording layer having a recording function and a reproducing layer having a reproducing function. In this case, the reproducing layer is preferably in contact with the column structure surface. Preferably, the magnetic part has a multilayer structure for realizing an MSR method, a MAMMOS method, or a DWDD method as a reproducing method. The present invention can be implemented in a magneto-optical recording medium having a recording layer made of a perpendicularly magnetized film, and particularly when implemented in an MSR, MAMMOS, and DWDD magneto-optical recording medium having excellent reproduction resolution. The profit is high.
According to the second aspect of the present invention, a light-transmitting base material, a magnetic part responsible for a recording function and a reproducing function, a light-transmitting property interposed between the base material and the magnetic part, and There is provided a method for producing a magneto-optical recording medium comprising an auxiliary layer having a column structure surface for increasing the perpendicular magnetic anisotropy of the magnetic part in contact with the magnetic part. This manufacturing method includes a step for forming a metal film on a substrate, an oxidation step for forming an auxiliary layer by oxidizing the metal film, and forming a magnetic material on the auxiliary layer. Forming a magnetic part. Here, the base material is a member that serves as a base on which an auxiliary layer is formed, and includes a substrate alone and a substrate on which a dielectric layer or the like is already formed on the laminated surface.
According to such a method, the magneto-optical recording medium according to the first aspect can be manufactured. Therefore, according to the second aspect of the present invention, the same effect as described above with respect to the first aspect can be achieved in the produced magneto-optical recording medium.
According to the third aspect of the present invention, a light-transmitting base material, a magnetic part responsible for a recording function and a reproducing function, a light-transmitting property interposed between the base material and the magnetic part, and Another method for manufacturing a magneto-optical recording medium comprising an auxiliary layer having a column structure surface for increasing the perpendicular magnetic anisotropy of the magnetic part in contact with the magnetic part is provided. The manufacturing method includes a step for forming a first metal film on a substrate, a first oxidation step for forming a first metal oxide film by oxidizing the first metal film, and a first A step for forming a second metal film on the metal oxide film; a second oxidation step for forming an auxiliary layer by oxidizing the second metal film to form a second metal oxide film; Forming a magnetic part by depositing a magnetic material on the auxiliary layer.
According to such a method, the magneto-optical recording medium according to the first aspect can be manufactured. Therefore, according to the third aspect of the present invention, the same effect as described above with respect to the first aspect can be obtained in the produced magneto-optical recording medium.
According to the fourth aspect of the present invention, the light-transmitting base material, the magnetic part responsible for the recording function and the reproducing function, the light-transmitting property interposed between the base material and the magnetic part, and Another method for manufacturing a magneto-optical recording medium comprising an auxiliary layer having a column structure surface for increasing the perpendicular magnetic anisotropy of the magnetic part in contact with the magnetic part is provided. The manufacturing method includes a step for forming a first metal film on a substrate, a step for forming a second metal film on the first metal film, and a first metal film and a second metal film. An oxidation process for forming an auxiliary layer by oxidation and a process for forming a magnetic part by forming a magnetic material on the auxiliary layer are included.
According to such a method, the magneto-optical recording medium according to the first aspect can be manufactured. Therefore, according to the fourth aspect of the present invention, the same effect as described above with respect to the first aspect can be obtained in the produced magneto-optical recording medium.
In the second to fourth aspects of the present invention, preferably, in the oxidation step, the metal film is exposed to an oxygen atmosphere. Alternatively, the metal film may be heated in the oxidation process. Alternatively, in the oxidation step, the metal film may be subjected to oxygen plasma etching. These techniques for oxidizing the metal once formed are suitable for forming a fine column structure.
The metal film in the second aspect of the present invention, and the first metal film and / or the second metal film in the third and fourth aspects are made of Ag, Al, Ni, Ti, Zr, Y, and Ru. A single metal selected from the group, or an alloy containing two or more metals selected from the group consisting of Ag, Al, Ni, Ti, Zr, Y, and Ru. These metals are suitable for forming an auxiliary layer having a fine column structure surface.

FIG. 1 is a schematic partial sectional view of a magneto-optical recording medium according to the first embodiment of the present invention.
FIG. 2 shows a laminated structure of the magneto-optical recording medium according to the present invention.
FIG. 3 is a schematic partial sectional view of a magneto-optical recording medium according to the second embodiment of the present invention.
FIG. 4 shows the laminated structure of the magneto-optical recording medium of Example 1.
FIG. 5 shows the laminated structure of the magneto-optical recording medium of Example 8.
FIG. 6 shows the laminated structure of the magneto-optical recording medium of Example 9.
FIG. 7 shows the laminated structure of the magneto-optical recording medium of Example 10.
FIG. 8 shows the laminated structure of the magneto-optical recording medium of Example 11.
FIG. 9 shows a laminated structure of the magneto-optical recording medium of Comparative Example 1.
FIG. 10 is an enlarged schematic cross-sectional view of the vicinity of the auxiliary layer surface in Example 1.
FIG. 11 is an enlarged schematic cross-sectional view of the vicinity of the surface of the dielectric layer in Comparative Example 1.
FIG. 12 is a table listing the average surface roughness Ra and the average column diameter in the auxiliary layers of Examples 1 to 7 and 11 and the dielectric layer of Comparative Example 1.
FIG. 13 shows the results of the characteristic evaluation in Example 1 and Comparative Example 1.
FIG. 14 shows the results of characteristic evaluation in Example 8 and Comparative Example 2.
FIG. 15 shows the results of characteristic evaluation in Example 9 and Comparative Example 3.
FIG. 16 shows the result of the characteristic evaluation in Example 10 and Comparative Example 4.
FIG. 17 shows the result of characteristic evaluation in Example 11 and Comparative Example 4.
FIG. 18 shows the thickness dependence of the average surface roughness Ra and the thickness dependence of the average column diameter for the auxiliary layer.

1 and 2 show a magneto-optical recording medium X1 according to the first embodiment of the present invention. The magneto-optical recording medium X1 is configured as a rewritable back-illuminated magneto-optical disk having two functions of thermomagnetic recording and reproduction utilizing the magneto-optical effect. A portion 11, an auxiliary layer 12, dielectric layers 13 and 14, and a heat dissipation layer 15 are provided. FIG. 1 schematically shows a partial cross section of the magneto-optical recording medium X1, and FIG. 2 shows a stacked configuration in a land portion and / or a groove portion used as an information track of the magneto-optical recording medium X1. .
The substrate S has a predetermined concavo-convex shape including lands and grooves, and is sufficiently transmissive to the recording laser and the reproducing laser of the magneto-optical recording medium X1. Such a substrate S is made of, for example, polycarbonate (PC) resin, polymethyl methacrylate (PMMA) resin, epoxy resin, or polyolefin resin.
The magnetic unit 11 has a magnetic structure composed of one or two or more magnetic films capable of performing two functions of thermomagnetic recording and reproduction utilizing the magneto-optical effect. Configure an information track. For example, the magnetic part 11 is composed of a single recording layer having both a recording function and a reproducing function. Alternatively, the magnetic part 11 has a two-layer structure including a recording layer having a relatively large coercive force and performing a recording function, and a reproducing layer having a relatively large Kerr rotation angle and a reproducing function. Have Alternatively, the magnetic unit 11 has a three-layer structure including a recording layer, a reproducing layer, and an intermediate layer therebetween for realizing the MSR method, the MAMMOS method, or the DWDD method.
Each layer in each structure that the magnetic part 11 can take is a perpendicular magnetization film made of an amorphous alloy of a rare earth element and a transition metal and magnetized in the perpendicular direction with perpendicular magnetic anisotropy. The vertical direction means a direction perpendicular to the film surface of the magnetic film constituting each layer. As the rare earth element, Tb, Gd, Dy, Nd, Pr, or the like can be used. As the transition metal, Fe, Co, or the like can be used.
More specifically, the recording layer is made of, for example, TbFeCo, DyFeCo, or TbDyFeCo having a predetermined composition. When the reproduction layer is provided, the reproduction layer is made of, for example, GdFeCo, GdDyFeCo, GdTbDyFeCo, NdDyFeCo, NdGdFeCo, or PrDyFeCo having a predetermined composition. When the intermediate layer is provided, the intermediate layer is made of, for example, GdFe, TbFe, GdFeCo, GdDyFeCo, GdTbDyFeCo, NdDyFeCo, NdGdFeCo, or PrDyFeCo having a predetermined composition. The thickness of each layer is determined according to the magnetic structure desired for the magnetic part 11.
The auxiliary layer 12 has a column structure 12 a for increasing the perpendicular magnetic anisotropy of the magnetic part 11 formed on the auxiliary layer 12 at the interface with the magnetic part 11. The column structure 12a includes a plurality of columns. The average diameter of the plurality of columns is preferably 5 to 35 nm. The average roughness Ra of the auxiliary layer surface having such a column structure is preferably 0.6 nm or less. The auxiliary layer 12 is sufficiently transmissive to the recording laser and the reproducing laser for the magneto-optical recording medium X1.
Such an auxiliary layer 12 having a column structure 12a for increasing the perpendicular magnetic anisotropy of the magnetic part 11 and having sufficient light transmittance is made of Ag, Al, Ni, Ti, Zr, Y, or Ru. It is made of an oxide or an oxide of an alloy containing a metal selected from Ag, Al, Ni, Ti, Zr, Y, and Ru. Preferably, the auxiliary layer 12 is made of Ag ₂ O, Al ₂ O ₃ , NiO, Ni ₂ O ₃ , TiO, TiO ₂ , ZrO, ZrO ₂ , Y ₂ O ₃ , RuO ₂ , Ru ₂ O ₃ , AlTiO, AlCrO. , NiRuO, or ZrRuO. The thickness of the auxiliary layer 12 is preferably in the range of 0.2 to 5.0 nm.
The dielectric layers 13 and 14 are portions for avoiding or suppressing the magnetic influence from the outside on the magnetic part 11 and are made of, for example, SiN, SiO ₂ , YSiO ₂ , ZnSiO ₂ , AlO, or AlN.
The heat dissipation layer 15 is a part for efficiently diffusing heat generated in the magnetic part 11 or the like at the time of laser irradiation. For example, Ag, Ag alloy, Al alloy (AlTi, AlCr, etc.), Au, or Pt It is made of high heat conductive material. The magneto-optical recording medium X1 may further have a predetermined protective film on the heat dissipation layer 15 as necessary.
In the manufacture of the magneto-optical recording medium X1 having such a structure, after the smoothing surface treatment is performed on the substrate S, the dielectric layer 13 is first laminated on the substrate S. The dielectric layer 13 is formed by a sputtering method using a single target or a plurality of targets made of a predetermined material.
Next, a predetermined metal is formed on the dielectric layer 13 by sputtering. The metal is a single metal of Ag, Al, Ni, Ti, Zr, Y, or Ru, or an alloy containing two or more metals selected from these metals.
Next, the formed metal film is oxidized. Due to the oxidation, the surface of the metal film becomes needle-like, that is, becomes finer. As a result, the auxiliary layer 12 is formed having the column structure 12a on the exposed surface. In this step, oxidation can be achieved by exposing the metal film to an oxygen atmosphere. Alternatively, in this step, the metal film may be heated. Alternatively, in this step, oxygen plasma etching may be performed on the metal film. Alternatively, in this step, the metal film may be oxidized by combining these oxidation techniques. When oxygen plasma etching is employed, a part of the metal film is removed by etching, so that the metal film formed in the previous step is formed thick in consideration of the amount removed by etching.
Next, the magnetic part 11 is formed on the auxiliary layer 12. Specifically, the magnetic part 11 is formed by laminating a predetermined magnetic material on the auxiliary layer 12 by sputtering according to the magnetic structure of the magnetic part 11.
Next, the dielectric layer 14 and the heat dissipation layer 15 are sequentially formed on the magnetic part 11 by sputtering. In this way, the magneto-optical recording medium X1 can be manufactured.
In the magneto-optical recording medium X1, a high recording density can be achieved. The magnetic part 11 of the magneto-optical recording medium X1 has a recording function and a reproducing function, and therefore includes at least a recording layer. The auxiliary layer 12 is interposed between the magnetic part 11 and the light-transmitting substrate S and has a contact surface with the magnetic part 11. The contact surface of the auxiliary layer 12 with the magnetic part 11 has a column structure 12a including a plurality of thin columns, and the magnetic part 11 is formed by depositing a predetermined magnetic material on the column structure 12a. Is done. By depositing and growing a magnetic material with a thin column on the surface of the auxiliary layer as a nucleus, a high perpendicular magnetic anisotropy can be obtained in the magnetic part 11 to be formed and thus the recording layer included therein. The higher the perpendicular magnetic anisotropy of the recording layer, the more stable recording marks can be formed, and as a result, it is suitable for improving the recording density of the recording layer.
The auxiliary layer 12 is light transmissive with respect to the recording laser and the reproducing laser. Therefore, the presence of the auxiliary layer 12 does not hinder the recording process and reproduction of the magneto-optical recording medium X1.
As described above, in the magneto-optical recording medium X1, the auxiliary layer 12 provided as the base film of the magnetic part 11 including the recording layer has the column structure 12a for increasing the perpendicular magnetic anisotropy of the magnetic part 11 and thus the recording layer. It has at the interface with the magnetic part 11 and has sufficient light transmittance. Therefore, according to the magneto-optical recording medium X1, a high recording density can be appropriately achieved. Such a magneto-optical recording medium is particularly effective when implemented as an MSR, MAMMOS, and DWDD magneto-optical disk having excellent reproduction resolution.
FIG. 3 is a schematic partial sectional view of a magneto-optical recording medium X2 according to the second embodiment of the present invention. The magneto-optical recording medium X2 includes a substrate S, a magnetic part 11, an auxiliary layer 20, dielectric layers 13 and 14, and a heat dissipation layer 15, and in a land part and / or a groove part used as an information track. Similar to the magneto-optical recording medium X1, it has a laminated structure as shown in FIG. The magneto-optical recording medium X2 differs from the magneto-optical recording medium X1 in that an auxiliary layer 20 different from the auxiliary layer 12 is provided, and the other configuration is the same as that of the magneto-optical recording medium X1.
The auxiliary layer 20 has a laminated structure including a metal oxide film 21 and a metal oxide film 22 thereon. The metal oxide film 21 has a column structure including a plurality of columns at the interface with the metal oxide film 22. In addition, the metal oxide film 22 has a column structure 22 a for increasing the perpendicular magnetic anisotropy of the magnetic part 11 formed on the layer at the interface with the magnetic part 11. The column structure 22a includes a plurality of columns. In this embodiment, the average diameter of the plurality of columns is 5 to 35 nm. In the present embodiment, the average roughness Ra of the surface of the auxiliary layer 12 having such a column structure is 0.6 nm or less.
The metal oxide films 21 and 22 constituting the auxiliary layer 12 are sufficiently transmissive to the recording laser and the reproducing laser for the magneto-optical recording medium X2.
As the constituent material of the metal oxide films 21 and 22, the metal oxide listed above as the constituent material of the auxiliary layer 12 in the first embodiment can be employed.
In the manufacture of the magneto-optical recording medium X2 having such a structure, the dielectric layer 13 is first formed on the substrate S subjected to the surface smoothing process in the same manner as described in the first embodiment. To do.
Next, in the first metal film forming step, a predetermined metal is formed on the dielectric layer 13 by sputtering. The metal is Ag, Al, Ni, Ti, Zr, Y, or Ru, or an alloy containing two or more metals selected from these. Next, in the first oxidation step, the formed metal film is oxidized. As a result, the metal oxide film 21 is formed.
Next, in the second metal film forming step, a predetermined metal is formed on the metal oxide film 21 by a sputtering method. The metal is Ag, Al, Ni, Ti, Zr, Y, or Ru, or an alloy containing two or more metals selected from these. Preferably, the metal film formed in the second metal film forming step is made of a chemical species different from the metal film formed in the first metal film forming step.
In forming the auxiliary layer 20, next, in the second oxidation step, the metal film formed in the second metal film formation step is oxidized. As a result, the metal oxide film 22 is formed having the column structure 22a on the exposed surface. The metal film oxidation method in the first and second oxidation steps is the same as that described above with respect to the oxidation step in the first embodiment.
The column structure 22a of the metal oxide film 22 tends to become more acicular or finer because the metal oxide film 22 is formed on the fine column structure of the metal oxide film 21. The column structure 22a of the metal oxide film 22 is considered to be grown on the column structure of the metal oxide film 21.
In the formation of the auxiliary layer 20, instead of the above-described method, before the metal film formed in the first metal film forming step is oxidized, the auxiliary layer 20 is further formed on the metal film in the second metal film forming step. The metal films may be laminated and then these two metal films may be oxidized in a single oxidation step. The metal material used in each metal film formation step and the oxidation method in the oxidation step are the same as those described above. Also by such a technique, the auxiliary layer 20 composed of the metal oxide film 21 and the metal oxide film 22 having a fine column structure 22a can be formed.
In the manufacture of the magneto-optical recording medium X2, next, on the auxiliary layer 20 formed in this manner, the magnetic portion 11, the dielectric layer 14, and the like, as described above with respect to the first embodiment, And the heat dissipation layer 15 is formed sequentially. In this way, the magneto-optical recording medium X2 can be manufactured.
In the magneto-optical recording medium X2, the auxiliary layer 20 provided as a base film for the magnetic part 11 including the recording layer has a column structure 22a for increasing the perpendicular magnetic anisotropy of the magnetic part 11 and thus the recording layer. And has sufficient light transmittance. Therefore, according to the magneto-optical recording medium X2, similarly to the magneto-optical recording medium X1, a high recording density can be appropriately achieved.
In addition, in the magneto-optical recording medium X2, since the metal oxide film 22 is laminated on the column structure of the metal oxide film 21, the column structure 22a of the metal oxide film 22 or the auxiliary layer 20 has a fine structure. It tends to become. The finer the column structure 22a, the higher the perpendicular magnetic anisotropy of the magnetic part 11 formed on the stacked structure.
Such a magneto-optical recording medium is particularly effective when implemented as an MSR, MAMMOS, and DWDD magneto-optical disk having excellent reproduction resolution.

A magneto-optical recording medium of this example was manufactured as a magneto-optical disk having the laminated structure shown in FIG. In the magneto-optical recording medium of this embodiment, the magnetic part is composed of a single recording layer.
In the production of the magneto-optical recording medium of this example, first, SiN is formed on a magneto-optical disk substrate (made of polycarbonate) by a DC magnetron sputtering method using a DC magnetron sputtering apparatus until the thickness becomes 75 nm. Was formed into a dielectric layer. Specifically, SiN was formed on the substrate by reactive sputtering performed using an Si target and using Ar gas and N ₂ gas as sputtering gas. The substrate has predetermined lands and grooves on the dielectric layer lamination surface. In this sputtering, the flow ratio of Ar gas and N ₂ gas was 2: 1, the sputtering gas pressure was 0.3 Pa, and the sputtering power was 0.5 kW. Subsequent film formation was also carried out by DC magnetron sputtering using the same apparatus.
Next, a metal film for forming an auxiliary layer was formed on the dielectric layer by depositing Ag to a thickness of 0.5 nm. In this sputtering, an Ag target was used, Ar gas was used as the sputtering gas, the sputtering gas pressure was 0.1 Pa, and the sputtering power was 0.5 kW.
Next, the metal film formed as described above was oxidized. Specifically, after introducing O ₂ gas into the sputtering chamber of the DC magnetron sputtering apparatus after forming the metal film, the metal film was allowed to stand for 3 minutes under the condition of a gas pressure of 1 Pa. It has been confirmed that the metal film can be oxidized by allowing the metal film to stand for 10 minutes under the condition of a gas pressure of 1 Pa after introducing O ₂ gas. It has also been confirmed that the metal film can be oxidized by leaving the metal film in the chamber for 10 minutes at a substrate temperature of 80 ° C. without introducing O ₂ gas. In addition, it has been confirmed that the oxidation of the metal film can be performed by oxygen plasma etching. In this case, for example, the oxygen gas pressure in the chamber is 0.5 Pa, and the etching time is 20 seconds.
In the production of the magneto-optical recording medium of this example, a recording layer was then formed by depositing a TbFeCo amorphous alloy (Tb ₂₀ Fe ₇₀ Co ₁₀ ) on the auxiliary layer until the thickness reached 25 nm. . In this sputtering, a TbFeCo alloy target was used, Ar gas was used as the sputtering gas, the sputtering gas pressure was 0.5 Pa, and the sputtering power was 0.5 kW. The Curie temperature of the formed Tb ₂₀ Fe ₇₀ Co ₁₀ recording layer was about 200 ° C.
Next, a dielectric layer was formed by depositing SiN on the recording layer to a thickness of 15 nm. The specific conditions are the same as described above with respect to the formation of the SiN dielectric layer described above in this embodiment.
Next, a heat dissipation layer was formed by depositing Ag on the dielectric layer until the thickness reached 30 nm. In this sputtering, an Ag target was used, Ar gas was used as the sputtering gas, the sputtering gas pressure was 0.1 Pa, and the sputtering power was 0.5 kW. As described above, the magneto-optical recording medium of this example was produced.

Examples 2-7

  The metal film for forming the auxiliary layer is replaced with the film formation of Ag, Al (Example 2), Ni (Example 3), Ti (Example 4), Zr (Example 5), Y (Example 6) ) Or Ru (Example 7), and the same conditions as in Example 1 except that the conditions (gas pressure and standing time) according to each metal film were changed in the subsequent oxidation treatment. From the formation of the dielectric layer (SiN, thickness 75 nm) to the formation of the heat dissipation layer (Ag, thickness 30 nm), the magneto-optical recording medium of each example was manufactured.

A magneto-optical recording medium of this example was manufactured as a magneto-optical disk having the laminated structure shown in FIG. In the magneto-optical recording medium of this example, the magnetic part has a two-layer structure including a recording layer and a reproducing layer.
In the production of the magneto-optical recording medium of this example, first, as in Example 1, a dielectric layer (SiN, thickness 75 nm) and an auxiliary layer (silver oxide, thickness) are formed on the magneto-optical disk substrate. 0.5 nm) were sequentially formed.
Next, a reproduction layer was formed by depositing a GdFeCo amorphous alloy (Gd ₂₂ Fe ₅₈ Co ₂₀ ) on the auxiliary layer to a thickness of 7 nm. In this sputtering, a GdFeCo alloy target was used, Ar gas was used as the sputtering gas, the sputtering gas pressure was 0.5 Pa, and the sputtering power was 0.5 kW.
Next, a recording layer was formed by depositing a TbFeCo amorphous alloy (Tb ₂₀ Fe ₇₀ Co ₁₀ ) on the reproducing layer to a thickness of 18 nm. In this sputtering, a TbFeCo alloy target was used, Ar gas was used as the sputtering gas, the sputtering gas pressure was 0.5 Pa, and the sputtering power was 0.5 kW. The Curie temperature of the formed Tb ₂₀ Fe ₇₀ Co ₁₀ recording layer was about 200 ° C.
Next, as in Example 1, a dielectric layer (SiN, thickness 15 nm) and a heat dissipation layer (Ag, thickness 30 nm) were sequentially formed on the recording layer. As described above, the magneto-optical recording medium of this example was produced. In the magneto-optical recording medium of the present example, the recording layer has a larger perpendicular coercivity than the reproducing layer, and the reproducing layer has a Kerr rotation angle in the reproducing laser larger than that of the recording layer.

A magneto-optical recording medium of this example was manufactured as an MSR type magneto-optical disk having the laminated structure shown in FIG. In the magneto-optical recording medium of the present embodiment, the magnetic part has a three-layer structure including a recording layer, a reproducing layer, and an intermediate layer between them in order to realize MSR reproduction.
In the production of the magneto-optical recording medium of this example, first, as in Example 1, a dielectric layer (SiN, thickness 75 nm) and an auxiliary layer (silver oxide, thickness) are formed on the magneto-optical disk substrate. 0.5 nm) were sequentially formed.
Next, a reproduction layer was formed by depositing a GdFeCo amorphous alloy (Gd ₂₅ Fe ₆₂ Co ₁₃ ) on the auxiliary layer until the thickness reached 40 nm. In this sputtering, a GdFeCo alloy target was used, Ar gas was used as the sputtering gas, the sputtering gas pressure was 0.5 Pa, and the sputtering power was 0.5 kW. The Curie temperature of the formed Gd ₂₅ Fe ₆₂ Co ₁₃ reproducing layer was about 300 ° C.
Next, an intermediate layer was formed by depositing a GdFe amorphous alloy (Gd ₃₁ Fe ₆₉ ) on the reproduction layer until the thickness reached 40 nm. In this sputtering, a GdFe alloy target was used, Ar gas was used as the sputtering gas, the sputtering gas pressure was 0.5 Pa, and the sputtering power was 0.5 kW. The Curie temperature of the formed Gd ₃₁ Fe ₆₉ intermediate layer was about 220 ° C.
Next, a recording layer was formed by depositing a TbFeCo amorphous alloy (Tb ₂₄ Fe ₅₉ Co ₁₇ ) on the intermediate layer until the thickness reached 50 nm. In this sputtering, a TbFeCo alloy target was used, Ar gas was used as the sputtering gas, the sputtering gas pressure was 0.5 Pa, and the sputtering power was 0.5 kW. The Curie temperature of the formed Tb ₂₄ Fe ₅₉ Co ₁₇ recording layer was about 280 ° C.
Next, as in Example 1, a dielectric layer (SiN, thickness 15 nm) and a heat dissipation layer (Ag, thickness 30 nm) were sequentially formed on the recording layer. As described above, the magneto-optical recording medium of this example was produced. In the magneto-optical recording medium of this example, the recording layer has a higher perpendicular coercivity than the reproducing layer, the reproducing layer has a larger Kerr rotation angle in the reproducing laser than the recording layer, and the intermediate layer has a Curie temperature higher than the other layers. Is low.

A magneto-optical recording medium of this example was manufactured as a MAMMOS type magneto-optical disk having the laminated structure shown in FIG. In the magneto-optical recording medium of the present embodiment, the magnetic part has a three-layer structure including a recording layer, a reproducing layer, and an intermediate layer between them in order to realize MAMMOS reproduction.
In the production of the magneto-optical recording medium of this example, first, as in Example 1, a dielectric layer (SiN, thickness 75 nm) and an auxiliary layer (silver oxide, thickness) are formed on the magneto-optical disk substrate. 0.5 nm) were sequentially formed.
Next, a reproduction layer of this example was formed by depositing a GdFeCo amorphous alloy (Gd ₂₇ Fe ₆₂ Co ₁₁ ) on the auxiliary layer to a thickness of 30 nm. In this sputtering, a GdFeCo alloy target was used, Ar gas was used as the sputtering gas, the sputtering gas pressure was 0.5 Pa, and the sputtering power was 0.5 kW. The Curie temperature of the formed Gd ₂₇ Fe ₆₂ Co ₁₁ reproducing layer was about 240 ° C.
Next, an intermediate layer of this example was formed by depositing a TbFeCo amorphous alloy (Tb ₂₀ Fe ₇₉ Co ₁ ) on the reproducing layer until the thickness reached 10 nm. In this sputtering, a TbFeCo alloy target was used, Ar gas was used as the sputtering gas, the sputtering gas pressure was 0.5 Pa, and the sputtering power was 0.5 kW. The Curie temperature of the formed Tb ₂₀ Fe 79 Co ₁ intermediate layer was about 130 ° C.
Next, a TbFeCo amorphous alloy (Tb ₂₇ Fe ₅₇ Co ₁₆ ) was formed on the intermediate layer to a thickness of 60 nm, thereby forming the recording layer of this example. In this sputtering, a TbFeCo alloy target was used, Ar gas was used as the sputtering gas, the sputtering gas pressure was 0.5 Pa, and the sputtering power was 0.5 kW. The Curie temperature of the formed Tb ₂₇ Fe ₅₇ Co ₁₆ recording layer was about 260 ° C.
Next, as in Example 1, a dielectric layer (SiN, thickness 15 nm) and a heat dissipation layer (Ag, thickness 30 nm) were sequentially formed on the recording layer. As described above, the magneto-optical recording medium of this example was produced. In the magneto-optical recording medium of this example, the recording layer has a higher perpendicular coercivity than the reproducing layer, the reproducing layer has a larger Kerr rotation angle in the reproducing laser than the recording layer, and the intermediate layer has a Curie temperature higher than the other layers. Is low.

A magneto-optical recording medium of this example was manufactured as a MAMMOS type magneto-optical disk having the laminated structure shown in FIG. In the magneto-optical recording medium of the present embodiment, the magnetic part has a three-layer structure including a recording layer, a reproducing layer, and an intermediate layer between them in order to realize MAMMOS reproduction.
In the production of the magneto-optical recording medium of this example, first, similarly to Example 1, a dielectric layer (SiN, thickness 75 nm) was formed on the magneto-optical disk substrate.
Next, a first metal film was formed by depositing Ag on the dielectric layer to a thickness of 0.5 nm. In this sputtering, an Ag target was used, Ar gas was used as the sputtering gas, the sputtering gas pressure was 0.1 Pa, and the sputtering power was 0.5 kW.
Next, a second metal film was formed by depositing Ru on the first metal film to a thickness of 0.5 nm. In this sputtering, a Ru target was used, Ar gas was used as the sputtering gas, the sputtering gas pressure was 0.2 Pa, and the sputtering power was 0.5 kW.
Next, the first and second metal films formed as described above were oxidized. Specifically, after introducing O ₂ gas into the sputtering chamber of the DC magnetron sputtering apparatus after forming the metal film, the metal film was allowed to stand for 15 minutes under the condition of a gas pressure of 1 Pa. In this manner, the auxiliary layer of this example having a laminated structure composed of the first metal oxide film and the second metal oxide film was formed.
Next, on the auxiliary layer, as in Example 10, the reproducing layer (Gd ₂₇ Fe ₆₂ Co ₁₁ , thickness 30 nm), the intermediate layer (Tb ₂₀ Fe ₇₉ Co ₁ , thickness 10 nm), and the recording layer (Tb ₂₇ Fe ₅₇ Co ₁₆ , thickness 60 nm), dielectric layer (SiN, thickness 15 nm), and heat dissipation layer (Ag, thickness 30 nm) were sequentially formed. As described above, the magneto-optical recording medium of this example was produced. In the magneto-optical recording medium of this example, the recording layer has a higher perpendicular coercivity than the reproducing layer, the reproducing layer has a larger Kerr rotation angle in the reproducing laser than the recording layer, and the intermediate layer has a Curie temperature higher than the other layers. Is low.

Examples 12-21

The thickness of the auxiliary layer (thickness of the metal film for forming the auxiliary layer) is changed to 0.5 nm, 0.1 nm (Example 12), 0.2 nm (Example 13), 0.7 nm (Example 14) ), 1.0 nm (Example 15), 1.5 nm (Example 16), 2.0 nm (Example 17), 3.0 nm (Example 18), 4.0 nm (Example 19), 5.0 nm Except for (Example 20) or 6.0 nm (Example 21), the formation of the dielectric layer (SiN, thickness 75 nm) to the formation of the heat dissipation layer (Ag, thickness 30 nm) are the same as in Example 1. Thus, the magneto-optical recording medium of each example was manufactured.
[Comparative Example 1]
A magneto-optical recording medium of this comparative example was manufactured as a magneto-optical disk having the laminated structure shown in FIG. Specifically, from the formation of the dielectric layer (SiN, thickness 75 nm) as in Example 1, except that the formation of the metal film for forming the auxiliary layer and the subsequent oxidation treatment were not performed, the heat dissipation layer ( The magneto-optical recording medium of this comparative example was manufactured by performing the process up to the formation of (Ag, thickness 30 nm).
[Comparative Examples 2 to 4]
A dielectric layer (SiN, thickness 75 nm) was formed in the same manner as in Example 8, Example 9, and Example 10 except that the formation of the metal film for forming the auxiliary layer and the subsequent oxidation treatment were not performed. The magneto-optical recording media of Comparative Example 2, Comparative Example 3, and Comparative Example 4 were produced by performing the formation to the formation of the heat dissipation layer (Ag, thickness 30 nm). Therefore, the magneto-optical recording medium of Comparative Example 2 has a laminated structure in which the auxiliary layer is removed from the magneto-optical recording medium of Example 8. Similarly, each magneto-optical recording medium of Comparative Examples 3 and 4 has a laminated structure in which the auxiliary layer is removed from the corresponding magneto-optical recording medium of Examples 9 and 10.
[Observation of auxiliary layer surface]
During the medium preparation process of Example 1, before forming the recording layer on the auxiliary layer, the surface of the auxiliary layer was observed using an atomic force microscope (manufactured by Seiko Instruments). The surface shape obtained by observation is schematically shown in FIG. In FIG. 10, the cross section of the auxiliary layer is hatched. A plurality of needle-like columns were formed on the surface of the auxiliary layer. The average surface roughness Ra of the auxiliary layer in Example 1 was 0.3 nm, and the average diameter of the column was 12 nm. The average diameter was determined by taking the diameter at the half height of the column as the diameter of each column. These results are listed in the table of FIG.
During the medium production process in Examples 2 to 7 and 11, the auxiliary layer surface was observed in the same manner as in Example 1 before forming the magnetic part on the auxiliary layer. For the auxiliary layer in each example, the average surface roughness Ra and column average diameter obtained by observation are listed in the table of FIG.
It has been confirmed that the column structure of the auxiliary layer in each example is substantially maintained on the exposed surface of the magnetic part (recording layer) formed on the auxiliary layer.
During the medium production process in Comparative Example 1, the surface of the dielectric layer was observed in the same manner as in Example 1 before forming the recording layer on the dielectric layer. The surface shape obtained by observation is schematically shown in FIG. In FIG. 11, the cross section of the surface of the dielectric layer is indicated by the same scale as FIG. 10 with hatching. In this comparative example, the average surface roughness Ra of the dielectric layer was 0.9 nm. When each convex shape was regarded as a column, the average diameter of the column was 53 nm. These results are listed in the table of FIG.
From the comparison between FIG. 10 and FIG. 11, it can be seen that the column structure on the surface of the auxiliary layer in Example 1 is more acicular or finer than the uneven shape on the surface of the dielectric layer in Comparative Example 1.
From the table of FIG. 12, it can be seen that the column structure on the surface of the auxiliary layer in Examples 1 to 7 is finer than the uneven shape on the surface of the dielectric layer in Comparative Example 1.
(Characteristic evaluation)
The recording / reproducing characteristics of the magneto-optical recording media of Examples 1, 8 to 11 and Comparative Examples 1 to 5 were examined.
For the magneto-optical recording medium of Example 1, first, a predetermined mark is passed through a sufficiently long space (space length: 2.0 μm) with respect to the information track in the magneto-optical recording medium (magneto-optical disk) of Example 1. A long recording mark was repeatedly recorded. The recording process was performed by a light modulation recording method using a read / write tester. The numerical aperture NA of the objective lens of this tester is 0.6, and the laser wavelength is 650 nm. In the recording process, the power of the recording laser was appropriately changed, the laser scanning speed was 6 m / s, and the applied magnetic field was 150 Oe. Next, the magneto-optical recording medium was reproduced, and the carrier level (C level) of the reproduction signal having the maximum intensity was measured. The reproduction process was performed using the same read / write tester, the laser power was 1.5 mW, the laser scanning speed was 6 m / s, and the applied magnetic field was 0 Oe. The C level of the reproduced signal was measured using a spectrum analyzer. Such recording processing and reproduction processing were performed for each mark length by changing the mark length of the recording mark. On the other hand, the recording / reproducing characteristics of the magneto-optical recording medium of Comparative Example 1 were examined under the same conditions. The result of the characteristic evaluation of each magneto-optical recording medium of Example 1 and Comparative Example 1 is shown in the graph of FIG. In the graph of FIG. 13, the horizontal axis represents the mark length, and the vertical axis represents the change from the C level when the mark length is sufficiently long. The same applies to the graphs of FIGS. 14 to 17 described later.
For the magneto-optical recording media of Example 8 and Comparative Example 2, the recording / reproducing characteristics were examined in the same manner as the magneto-optical recording medium of Example 1. The result of the characteristic evaluation of each magneto-optical recording medium of Example 8 and Comparative Example 2 is shown in the graph of FIG.
For the magneto-optical recording medium of Example 9, first, a recording mark having a predetermined mark length was repeatedly recorded on the information track in the magneto-optical recording medium of Example 9. The recording process was performed by the light modulation recording method using the same read / write tester as used in Example 1. In the recording process, the power of the recording laser was appropriately changed, the laser scanning speed was 6 m / s, and the applied magnetic field was 300 Oe. Next, the magneto-optical recording medium was reproduced using the same read / write tester, and the C level of the reproduced signal was measured. In the reproduction process, the laser power was 2.7 mW, the laser scanning speed was 6 m / s, and the applied magnetic field was 300 Oe. The C level of the reproduced signal was measured using a spectrum analyzer. Such recording processing and reproduction processing were performed for each mark length by changing the mark length of the recording mark. The magneto-optical recording medium of Comparative Example 3 was also examined for recording / reproducing characteristics under the same conditions. The result of the characteristic evaluation of each magneto-optical recording medium of Example 9 and Comparative Example 3 is shown in the graph of FIG.
For the magneto-optical recording medium of Example 10, first, a recording mark having a predetermined mark length was repeatedly recorded on the information track in the magneto-optical recording medium of Example 10. The recording process was performed by a laser strobe magnetic field recording method using the same read / write tester as used in Example 1. In the recording process, the power of the recording laser was 10 mW, the laser scanning speed was 6 m / s, and the applied magnetic field was 250 Oe. Next, the magneto-optical recording medium was reproduced using the same read / write tester, and the C level of the reproduced signal was measured. In the reproduction process, the laser power was 2.2 mW, the laser scanning speed was 6 m / s, and the applied magnetic field was 0 Oe. The C level of the reproduced signal was measured using a spectrum analyzer. Such recording processing and reproduction processing were performed for each mark length by changing the mark length of the recording mark. The magneto-optical recording medium of Comparative Example 4 was also examined for recording / reproducing characteristics under the same conditions. The result of the characteristic evaluation of each magneto-optical recording medium of Example 10 and Comparative Example 4 is shown in the graph of FIG.
For the magneto-optical recording medium of Example 11, the recording / reproducing characteristics were examined under the same conditions as for the magneto-optical recording medium of Example 10. The result of the characteristic evaluation of the magneto-optical recording medium of Example 11 is shown in the graph of FIG. 17 together with the result of Comparative Example 4.
As shown in the graphs of FIGS. 13 to 17, when reproducing a recording mark having a short mark length, the magneto-optical recording medium according to the embodiment of the present invention has the same stacked structure except that it does not have an auxiliary layer. The C level is higher than that of the magneto-optical recording medium according to the comparative example. Therefore, it can be seen that the magneto-optical recording media of Examples 1 and 8 to 11 are more advantageous for stably recording recording marks having a shorter mark length than the corresponding magneto-optical recording media of Comparative Examples 1 to 4. .
[Dependence of column structure on auxiliary layer thickness]
Before forming the recording layer on the auxiliary layer during the medium preparation process of Examples 12 to 21 having different auxiliary layer thicknesses, the surface of the auxiliary layer was formed using an atomic force microscope (manufactured by Seiko Instruments). The average surface roughness Ra and the average column diameter of each auxiliary layer were observed. The result is shown in the graph of FIG. In the graph, the horizontal axis represents the auxiliary layer thickness, the left vertical axis represents the average surface roughness Ra, and the right vertical axis represents the average column diameter. The two plots at the auxiliary layer thickness of 0 nm correspond to the data for Comparative Example 1 listed in the table of FIG. In the graph of FIG. 18, the line 31 represents the dependence of the average surface roughness Ra on the auxiliary layer thickness, and the line 32 represents the dependence of the average column diameter on the auxiliary layer thickness.
As shown in the graph of FIG. 18, the average surface roughness Ra and the column diameter both suddenly decrease when the auxiliary layer thickness is between 0.1 nm and 0.2 nm, and the auxiliary layer thickness is 0.2 nm. Both are small enough. In addition, when the auxiliary layer thickness exceeds 5 nm, the column diameter is particularly significantly increased. Thus, it can be seen from the graph of FIG. 18 that the column structure on the surface of the auxiliary layer is fine when the auxiliary layer thickness is in the range of 0.2 to 0.5 nm. Therefore, in the present invention, it can be understood that the auxiliary layer thickness is preferably in the range of 0.2 to 5.0 nm.

[Document Name] Description [Claims]
1. A substrate having optical transparency;
A magnetic part for recording and reproducing functions;
Having a light-transmitting property interposed between the base material and the magnetic part, and having a column structure surface for increasing the perpendicular magnetic anisotropy of the magnetic part in contact with the magnetic part;
A magneto-optical recording medium comprising: an auxiliary layer.
2. A light-transmitting base material, a magnetic part responsible for a recording function and a reproducing function, a light-transmitting substance interposed between the base material and the magnetic part, and the magnetic part An auxiliary layer having a column structure surface for increasing the perpendicular magnetic anisotropy of the magnetic part in contact with the magneto-optical recording medium,
Forming a metal film on the substrate;
An oxidation step for forming the auxiliary layer by oxidizing the metal film;
Forming the magnetic part by depositing a magnetic material on the auxiliary layer.
3. A light-transmitting base material, a magnetic part for recording and reproducing functions, a light-transmitting material interposed between the base material and the magnetic part, and the magnetic part An auxiliary layer having a column structure surface for increasing the perpendicular magnetic anisotropy of the magnetic part in contact with the magneto-optical recording medium,
Forming a first metal film on the substrate;
A first oxidation step for forming a first metal oxide film by oxidizing the first metal film;
Forming a second metal film on the first metal oxide film;
A second oxidation step for forming the auxiliary layer by oxidizing the second metal film to form a second metal oxide film;
Forming the magnetic part by depositing a magnetic material on the auxiliary layer.
4. A light-transmitting base material, a magnetic part for recording and reproducing functions, a light-transmitting material interposed between the base material and the magnetic part, and the magnetic part An auxiliary layer having a column structure surface for increasing the perpendicular magnetic anisotropy of the magnetic part in contact with the magneto-optical recording medium,
Forming a first metal film on the substrate;
Forming a second metal film on the first metal film;
Forming the auxiliary layer by oxidizing the first metal film and the second metal film;
Forming the magnetic part by depositing a magnetic material on the auxiliary layer.
DETAILED DESCRIPTION OF THE INVENTION
[0001]
【Technical field】
The present invention relates to a back-illuminated magneto-optical recording medium and a manufacturing method thereof.
[0002]
[Background]
In recent years, magneto-optical recording media have attracted attention. The magneto-optical recording medium is a rewritable recording medium that is configured using various magnetic properties of a magnetic material and has two functions of thermomagnetic recording and reproduction using a magneto-optical effect. The magneto-optical recording medium has a recording layer made of a perpendicular magnetization film, and a predetermined signal is recorded in the recording layer as a change in the magnetization direction. This recording signal is read by a predetermined optical system for reading a reproduction signal. Such a magneto-optical recording medium is disclosed in, for example, Japanese Patent Application Laid-Open Nos. 6-111405 and 6-290496.
[0003]
In the field of magneto-optical recording media, various reproducing systems have been developed for practically reproducing signals recorded at a high density exceeding the limit of resolution in an optical system for reading reproduced signals. For example, MSR (magnetic super resolution), MAMMOS (magnetic amplifying magneto-optical system), and DWDD (domain wall displacement detection).
[0004]
In a DWDD type magneto-optical recording medium, a magnetic material portion having a laminated structure of a recording layer, a reproducing layer, and an intermediate layer therebetween is provided on a predetermined substrate. Each of these three layers is a perpendicular magnetization film generally made of a rare earth-transition metal amorphous alloy, and is laminated so that exchange interaction works between two adjacent layers when not heated. The recording layer exhibits a relatively large domain wall coercivity, the reproducing layer exhibits a relatively small domain wall coercivity, and the intermediate layer has a lower Curie temperature than the other two layers.
[0005]
A predetermined signal is recorded on the recording layer along the scanning direction of the medium. Specifically, the recording layer is formed with a plurality of magnetic domains each having a predetermined length corresponding to a recording signal, the magnetization of which is alternately reversed continuously in the medium scanning direction. A plurality of domain walls standing at intervals corresponding to the recording signal are formed along the. In the reproducing layer and the intermediate layer, the recording layer and the reproducing layer are exchange-coupled via the intermediate layer under a temperature condition where the medium temperature is lower than the Curie temperature of the intermediate layer, and the medium temperature exceeds the Curie temperature of the intermediate layer. Under a predetermined temperature condition, the domain wall motion phenomenon occurs in the reproducing layer. Under a temperature condition where the medium temperature is lower than the Curie temperature of the intermediate layer, the reproducing layer exchange-coupled to the recording layer via the intermediate layer includes a magnetic domain magnetized in the same direction as the recording layer and a domain wall in the magnetic domain. And are fixed. Under a temperature condition in which the medium temperature is higher than the Curie temperature of the intermediate layer, the spontaneous magnetization of the intermediate layer disappears, and the exchange coupling between the recording layer and the reproducing layer via the intermediate layer is broken. As a result, the domain wall can move in the reproducing layer having a small domain wall coercive force. The domain wall moves to a higher temperature region when a temperature gradient exists in the reproducing layer.
[0006]
In the reproducing operation of the DWDD type magneto-optical disk in which the information track made of the magnetic material portion having the above-described configuration is formed, the information track is irradiated with a reproducing laser beam while rotating the disk. Scan the information track. At this time, a temperature gradient is generated in the scanning direction in the beam irradiation region inside the information track made of the magnetic material portion. In the beam irradiation region, the magnetic wall moves to the higher temperature side in the reproducing layer at the moment when the magnetic wall of the reproducing layer passes the isothermal line of the Curie temperature in the beam irradiation region from the low temperature region to the high temperature region with the scanning. To do. When the domain wall moves in the reproducing layer in this way, the magnetization of the domain wall moving region is reversed. By detecting this magnetization reversal with a predetermined optical system as a change in the polarization plane of the reflected light, the domain wall motion is detected. By irradiating the reproducing laser beam along the information track and sequentially detecting the domain wall movement, the recording signal of the medium is read.
[0007]
In reproduction based on such a DWDD system, not the entire spot of the reproduction laser beam, but the isotherm in the beam spot (the isotherm of the Curie temperature of the intermediate layer) of the reproduction layer or the recording layer constituting the information track. Record patterns are discriminated. Therefore, in the DWDD system, even a signal recorded at a high density on the recording layer exceeding the resolution limit in the optical system for reading the reproduction signal, that is, with a recording pattern in which the minimum recording mark length is smaller than the spot diameter. Even if it exists, it can be played back. For example, even when a red laser (beam spot diameter: about 1 μm) is adopted as a reproducing laser beam, a recording mark having a length of 0.1 μm or less can be reproduced.
[0008]
In the magneto-optical recording medium, the recording density increases as the length of the stable recording mark formed in the recording layer decreases. In the above-described MSR, MAMMOS, and DWDD magneto-optical recording media, there is a particularly strong demand for a high recording density of the recording layer in order to fully exhibit these reproduction resolutions. For example, a recording layer capable of stably recording continuous recording marks having a length of 0.1 μm or less is desired.
[0009]
In order to form such a minute recording mark, it is necessary to refine the structure of the recording layer. That is, in the recording layer, it is necessary to obtain a magnetic state in which minute magnetic domains can be stably formed by increasing the perpendicular magnetic anisotropy.
[0010]
In the technical field of magnetic materials, it is known that the magnetic state or magnetic properties of a magnetic film can be influenced by the underlying film on which the magnetic film is formed. Therefore, for example, in a magnetic recording medium that does not involve light irradiation during recording and reproduction, underlayers made of various materials are employed in order to adjust the magnetic state of the recording layer (magnetic film) as desired.
[0011]
However, in the conventional back-illuminated conventional magneto-optical recording medium with light irradiation from the substrate side at the time of recording and reproduction, the conventional underlayer used in the magnetic recording medium is replaced with the perpendicular magnetic anisotropy of the recording layer. It is not realistic to adopt for improvement. In the magneto-optical recording medium, the recording and reproducing light (laser) needs to be sufficiently transmitted between the substrate and the magnetic material portion including the recording layer. This is because the conventional base film does not have sufficient light transmission.
[0012]
DISCLOSURE OF THE INVENTION
The present invention has been conceived under such circumstances, and an object thereof is to achieve a high recording density in a back-illuminated magneto-optical recording medium.
[0013]
According to a first aspect of the present invention, a magneto-optical recording medium is provided. This magneto-optical recording medium has a light-transmitting base material, a magnetic part responsible for a recording function and a reproducing function, and has a light-transmitting property interposed between the base material and the magnetic part. And an auxiliary layer having a column structure surface for increasing the perpendicular magnetic anisotropy of the magnetic part. “Being light transmissive” means sufficiently transmitting the recording laser and reproducing laser irradiated to the magnetic part of the magneto-optical recording medium.
[0014]
According to such a configuration, a high recording density can be achieved in a back-illuminated magneto-optical recording medium. The magnetic part in the first aspect of the present invention has a recording function and a reproducing function, and therefore includes at least a recording layer. The auxiliary layer is interposed between such a magnetic part and the base material and has a surface in contact with the magnetic part. That is, in the magneto-optical recording medium of the present invention in which each layer is sequentially formed by depositing a material from the substrate side, the magnetic part is formed using the auxiliary layer as a base film. In the present invention, the contact surface of the auxiliary layer with the magnetic part has a column structure including a plurality of thin columns, and the magnetic part is formed by depositing a predetermined magnetic material on the column structure. . By depositing and growing a magnetic material using a thin column on the surface of the auxiliary layer as a nucleus, that is, a base point, a high perpendicular magnetic anisotropy can be obtained in the magnetic portion to be formed, and in the recording layer included therein. The higher the perpendicular magnetic anisotropy of the recording layer, the more stable recording marks can be formed in the recording layer, and as a result, it is suitable for improving the recording density of the recording layer.
[0015]
The auxiliary layer is light transmissive with respect to the recording laser and the reproducing laser. Therefore, the presence of the auxiliary layer does not hinder the recording process and reproduction of the magneto-optical recording medium.
[0016]
As described above, in the magneto-optical recording medium according to the first aspect of the present invention, the auxiliary layer provided as the base film of the magnetic part including the recording layer increases the perpendicular magnetic anisotropy of the magnetic part and thus the recording layer. The column structure is provided at the interface with the magnetic part and has sufficient light transmittance. Therefore, according to the magneto-optical recording medium according to the first aspect, it is possible to appropriately achieve a high recording density.
[0017]
In the first aspect of the present invention, preferably, the column structure surface has a plurality of columns, and the average diameter of the plurality of columns is 5 to 35 nm. In this case, the column structure surface preferably has an average surface roughness Ra of 0.6 nm or less. According to such a fine column structure, the perpendicular magnetic anisotropy of the magnetic part, that is, the recording layer can be appropriately ensured.
[0018]
Preferably, the auxiliary layer is made of a metal oxide. In this case, preferably, the metal oxide is an oxide of a metal selected from the group consisting of Ag, Al, Ni, Ti, Zr, Y, and Ru, or Ag, Al, Ni, Ti, Zr, Y And an oxide of an alloy containing a metal selected from the group consisting of Ru. The auxiliary layer of the present invention can be appropriately formed from such metal oxides.
[0019]
Preferably, the auxiliary layer has a thickness of 0.2-5 nm. From the viewpoint of sufficiently growing the column structure at the contact surface of the auxiliary layer with the magnetic part when forming the auxiliary layer by sputtering or the like, and ensuring the light transmittance of the auxiliary layer, the thickness of the auxiliary layer is Such a range is preferable.
[0020]
Preferably, the auxiliary layer is composed of two or more metal oxide films. In this case, it is preferable that two adjacent metal oxide films have different chemical compositions. By stacking metal oxide films, it may be possible to grow each column on the column structure surface of the auxiliary layer to be elongated.
[0021]
Preferably, the magnetic part has a multilayer structure including a recording layer having a recording function and a reproducing layer having a reproducing function. In this case, the reproducing layer is preferably in contact with the column structure surface. Preferably, the magnetic part has a multilayer structure for realizing an MSR method, a MAMMOS method, or a DWDD method as a reproducing method. The present invention can be implemented in a magneto-optical recording medium having a recording layer made of a perpendicularly magnetized film, and particularly when implemented in an MSR, MAMMOS, and DWDD magneto-optical recording medium having excellent reproduction resolution. The profit is high.
[0022]
According to the second aspect of the present invention, a light-transmitting base material, a magnetic part responsible for a recording function and a reproducing function, a light-transmitting property interposed between the base material and the magnetic part, and There is provided a method for producing a magneto-optical recording medium comprising an auxiliary layer having a column structure surface for increasing the perpendicular magnetic anisotropy of the magnetic part in contact with the magnetic part. This manufacturing method includes a step for forming a metal film on a substrate, an oxidation step for forming an auxiliary layer by oxidizing the metal film, and forming a magnetic material on the auxiliary layer. Forming a magnetic part. Here, the base material is a member that serves as a base on which an auxiliary layer is formed, and includes a substrate alone and a substrate on which a dielectric layer or the like is already formed on the laminated surface.
[0023]
According to such a method, the magneto-optical recording medium according to the first aspect can be manufactured. Therefore, according to the second aspect of the present invention, the same effect as described above with respect to the first aspect can be achieved in the produced magneto-optical recording medium.
[0024]
According to the third aspect of the present invention, a light-transmitting base material, a magnetic part responsible for a recording function and a reproducing function, a light-transmitting property interposed between the base material and the magnetic part, and Another method for manufacturing a magneto-optical recording medium comprising an auxiliary layer having a column structure surface for increasing the perpendicular magnetic anisotropy of the magnetic part in contact with the magnetic part is provided. The manufacturing method includes a step for forming a first metal film on a substrate, a first oxidation step for forming a first metal oxide film by oxidizing the first metal film, and a first A step for forming a second metal film on the metal oxide film; a second oxidation step for forming an auxiliary layer by oxidizing the second metal film to form a second metal oxide film; Forming a magnetic part by depositing a magnetic material on the auxiliary layer.
[0025]
According to such a method, the magneto-optical recording medium according to the first aspect can be manufactured. Therefore, according to the third aspect of the present invention, the same effect as described above with respect to the first aspect can be obtained in the produced magneto-optical recording medium.
[0026]
According to the fourth aspect of the present invention, the light-transmitting base material, the magnetic part responsible for the recording function and the reproducing function, the light-transmitting property interposed between the base material and the magnetic part, and Another method for manufacturing a magneto-optical recording medium comprising an auxiliary layer having a column structure surface for increasing the perpendicular magnetic anisotropy of the magnetic part in contact with the magnetic part is provided. The manufacturing method includes a step for forming a first metal film on a substrate, a step for forming a second metal film on the first metal film, and a first metal film and a second metal film. An oxidation process for forming an auxiliary layer by oxidation and a process for forming a magnetic part by forming a magnetic material on the auxiliary layer are included.
[0027]
According to such a method, the magneto-optical recording medium according to the first aspect can be manufactured. Therefore, according to the fourth aspect of the present invention, the same effect as described above with respect to the first aspect can be obtained in the produced magneto-optical recording medium.
[0028]
In the second to fourth aspects of the present invention, preferably, in the oxidation step, the metal film is exposed to an oxygen atmosphere. Alternatively, the metal film may be heated in the oxidation process. Alternatively, in the oxidation step, the metal film may be subjected to oxygen plasma etching. These techniques for oxidizing the metal once formed are suitable for forming a fine column structure.
[0029]
The metal film in the second aspect of the present invention, and the first metal film and / or the second metal film in the third and fourth aspects are made of Ag, Al, Ni, Ti, Zr, Y, and Ru. A single metal selected from the group, or an alloy containing two or more metals selected from the group consisting of Ag, Al, Ni, Ti, Zr, Y, and Ru. These metals are good applicable in forming the auxiliary layer having a fine column structure surface.
[0030]
BEST MODE FOR CARRYING OUT THE INVENTION
1 and 2 show a magneto-optical recording medium X1 according to the first embodiment of the present invention. The magneto-optical recording medium X1 is configured as a rewritable back-illuminated magneto-optical disk having two functions of thermomagnetic recording and reproduction utilizing the magneto-optical effect. A portion 11, an auxiliary layer 12, dielectric layers 13 and 14, and a heat dissipation layer 15 are provided. FIG. 1 schematically shows a partial cross section of the magneto-optical recording medium X1, and FIG. 2 shows a stacked configuration in a land portion and / or a groove portion used as an information track of the magneto-optical recording medium X1. .
[0031]
The substrate S has a predetermined concavo-convex shape including lands and grooves, and is sufficiently transmissive to the recording laser and the reproducing laser of the magneto-optical recording medium X1. Such a substrate S is made of, for example, polycarbonate (PC) resin, polymethyl methacrylate (PMMA) resin, epoxy resin, or polyolefin resin.
[0032]
The magnetic unit 11 has a magnetic structure composed of one or two or more magnetic films capable of performing two functions of thermomagnetic recording and reproduction utilizing the magneto-optical effect. Configure an information track. For example, the magnetic part 11 is composed of a single recording layer having both a recording function and a reproducing function. Alternatively, the magnetic part 11 has a two-layer structure including a recording layer having a relatively large coercive force and performing a recording function, and a reproducing layer having a relatively large Kerr rotation angle and a reproducing function. Have Alternatively, the magnetic unit 11 has a three-layer structure including a recording layer, a reproducing layer, and an intermediate layer therebetween for realizing the MSR method, the MAMMOS method, or the DWDD method.
[0033]
Each layer in each structure that the magnetic part 11 can take is a perpendicular magnetization film made of an amorphous alloy of a rare earth element and a transition metal and magnetized in the perpendicular direction with perpendicular magnetic anisotropy. The vertical direction means a direction perpendicular to the film surface of the magnetic film constituting each layer. As the rare earth element, Tb, Gd, Dy, Nd, Pr, or the like can be used. As the transition metal, Fe, Co, or the like can be used.
[0034]
More specifically, the recording layer is made of, for example, TbFeCо, DyFeCо, or TbDyFeCо having a predetermined composition. When the reproduction layer is provided, the reproduction layer is made of, for example, GdFeCо, GdDyFeCо, GdTbDyFeCо, NdDyFeCо, NdGdFeCо, or PrDyFeCо having a predetermined composition. When providing the intermediate layer, the intermediate layer is made of, for example, GdFe, TbFe, GdFeCо, GdDyFeCо, GdTbDyFeCо, NdDyFeCо, NdGdFeCо, or PrDyFeCо having a predetermined composition. The thickness of each layer is determined according to the magnetic structure desired for the magnetic part 11.
[0035]
The auxiliary layer 12 has a column structure 12 a for increasing the perpendicular magnetic anisotropy of the magnetic part 11 formed on the auxiliary layer 12 at the interface with the magnetic part 11. The column structure 12a includes a plurality of columns. The average diameter of the plurality of columns is preferably 5 to 35 nm. The average roughness Ra of the auxiliary layer surface having such a column structure is preferably 0.6 nm or less. The auxiliary layer 12 is sufficiently transmissive to the recording laser and the reproducing laser for the magneto-optical recording medium X1.
[0036]
Such an auxiliary layer 12 having a column structure 12a for increasing the perpendicular magnetic anisotropy of the magnetic part 11 and having sufficient light transmittance is made of Ag, Al, Ni, Ti, Zr, Y, or Ru. It is made of an oxide or an oxide of an alloy containing a metal selected from Ag, Al, Ni, Ti, Zr, Y, and Ru. Preferably, the auxiliary layer 12 is made of Ag ₂ O, Al ₂ O ₃ , NiO, Ni ₂ O ₃ , TiO, TiO ₂ , ZrO, ZrO ₂ , Y ₂ O ₃ , RuO ₂ , Ru ₂ O ₃ , AlTiO, AlCrO. , NiRuO, or ZrRuO. The thickness of the auxiliary layer 12 is preferably in the range of 0.2 to 5.0 nm.
[0037]
The dielectric layers 13 and 14 are portions for avoiding or suppressing an external magnetic influence on the magnetic part 11 and are made of, for example, SiN, SiO ₂ , YSiO ₂ , ZnSiO ₂ , AlO, or AlN.
[0038]
The heat dissipation layer 15 is a part for efficiently diffusing heat generated in the magnetic part 11 or the like at the time of laser irradiation. For example, Ag, Ag alloy, Al alloy (AlTi, AlCr, etc.), Au, or Pt It is made of high heat conductive material. The magneto-optical recording medium X1 may further have a predetermined protective film on the heat dissipation layer 15 as necessary.
[0039]
In the manufacture of the magneto-optical recording medium X1 having such a structure, after the smoothing surface treatment is performed on the substrate S, the dielectric layer 13 is first laminated on the substrate S. The dielectric layer 13 is formed by a sputtering method using a single target or a plurality of targets made of a predetermined material.
[0040]
Next, a predetermined metal is formed on the dielectric layer 13 by sputtering. The metal is a single metal of Ag, Al, Ni, Ti, Zr, Y, or Ru, or an alloy containing two or more metals selected from these metals.
[0041]
Next, the formed metal film is oxidized. Due to the oxidation, the surface of the metal film becomes needle-like, that is, becomes finer. As a result, the auxiliary layer 12 is formed having the column structure 12a on the exposed surface. In this step, oxidation can be achieved by exposing the metal film to an oxygen atmosphere. Alternatively, in this step, the metal film may be heated. Alternatively, in this step, oxygen plasma etching may be performed on the metal film. Alternatively, in this step, the metal film may be oxidized by combining these oxidation techniques. When oxygen plasma etching is employed, a part of the metal film is removed by etching, so that the metal film formed in the previous step is formed thick in consideration of the amount removed by etching.
[0042]
Next, the magnetic part 11 is formed on the auxiliary layer 12. Specifically, the magnetic part 11 is formed by laminating a predetermined magnetic material on the auxiliary layer 12 by sputtering according to the magnetic structure of the magnetic part 11.
[0043]
Next, the dielectric layer 14 and the heat dissipation layer 15 are sequentially formed on the magnetic part 11 by sputtering. In this way, the magneto-optical recording medium X1 can be manufactured.
[0044]
In the magneto-optical recording medium X1, a high recording density can be achieved. The magnetic part 11 of the magneto-optical recording medium X1 has a recording function and a reproducing function, and therefore includes at least a recording layer. The auxiliary layer 12 is interposed between the magnetic part 11 and the light-transmitting substrate S and has a contact surface with the magnetic part 11. The contact surface of the auxiliary layer 12 with the magnetic part 11 has a column structure 12a including a plurality of thin columns, and the magnetic part 11 is formed by depositing a predetermined magnetic material on the column structure 12a. Is done. By depositing and growing a magnetic material with a thin column on the surface of the auxiliary layer as a nucleus, a high perpendicular magnetic anisotropy can be obtained in the magnetic part 11 to be formed and thus the recording layer included therein. The higher the perpendicular magnetic anisotropy of the recording layer, the more stable recording marks can be formed, and as a result, it is suitable for improving the recording density of the recording layer.
[0045]
The auxiliary layer 12 is light transmissive with respect to the recording laser and the reproducing laser. Therefore, the presence of the auxiliary layer 12 does not hinder the recording process and reproduction of the magneto-optical recording medium X1.
[0046]
As described above, in the magneto-optical recording medium X1, the auxiliary layer 12 provided as the base film of the magnetic part 11 including the recording layer has the column structure 12a for increasing the perpendicular magnetic anisotropy of the magnetic part 11 and thus the recording layer. It has at the interface with the magnetic part 11 and has sufficient light transmittance. Therefore, according to the magneto-optical recording medium X1, a high recording density can be appropriately achieved. Such a magneto-optical recording medium is particularly effective when implemented as an MSR, MAMMOS, and DWDD magneto-optical disk having excellent reproduction resolution.
[0047]
FIG. 3 is a schematic partial sectional view of a magneto-optical recording medium X2 according to the second embodiment of the present invention. The magneto-optical recording medium X2 includes a substrate S, a magnetic part 11, an auxiliary layer 20, dielectric layers 13 and 14, and a heat dissipation layer 15, and in a land part and / or a groove part used as an information track. Similar to the magneto-optical recording medium X1, it has a laminated structure as shown in FIG. The magneto-optical recording medium X2 differs from the magneto-optical recording medium X1 in that an auxiliary layer 20 different from the auxiliary layer 12 is provided, and the other configuration is the same as that of the magneto-optical recording medium X1.
[0048]
The auxiliary layer 20 has a laminated structure including a metal oxide film 21 and a metal oxide film 22 thereon. The metal oxide film 21 has a column structure including a plurality of columns at the interface with the metal oxide film 22. In addition, the metal oxide film 22 has a column structure 22 a for increasing the perpendicular magnetic anisotropy of the magnetic part 11 formed on the layer at the interface with the magnetic part 11. The column structure 22a includes a plurality of columns. In this embodiment, the average diameter of the plurality of columns is 5 to 35 nm. In the present embodiment, the average roughness Ra of the surface of the auxiliary layer 20 having such a column structure is 0.6 nm or less.
[0049]
The metal oxide films 21 and 22 constituting the auxiliary layer 20 are sufficiently transmissive to the recording laser and the reproducing laser for the magneto-optical recording medium X2.
[0050]
As the constituent material of the metal oxide films 21 and 22, the metal oxide listed above as the constituent material of the auxiliary layer 12 in the first embodiment can be adopted.
[0051]
In the manufacture of the magneto-optical recording medium X2 having such a structure, the dielectric layer 13 is first formed on the substrate S subjected to the surface smoothing process in the same manner as described in the first embodiment. To do.
[0052]
Next, in the first metal film forming step, a predetermined metal is formed on the dielectric layer 13 by sputtering. The metal is Ag, Al, Ni, Ti, Zr, Y, or Ru, or an alloy containing two or more metals selected from these. Next, in the first oxidation step, the formed metal film is oxidized. As a result, the metal oxide film 21 is formed.
[0053]
Next, in the second metal film forming step, a predetermined metal is formed on the metal oxide film 21 by a sputtering method. The metal is Ag, Al, Ni, Ti, Zr, Y, or Ru, or an alloy containing two or more metals selected from these. Preferably, the metal film formed in the second metal film forming step is made of a chemical species different from the metal film formed in the first metal film forming step.
[0054]
In forming the auxiliary layer 20, next, in the second oxidation step, the metal film formed in the second metal film formation step is oxidized. As a result, the metal oxide film 22 is formed having the column structure 22a on the exposed surface. The metal film oxidation method in the first and second oxidation steps is the same as that described above with respect to the oxidation step in the first embodiment.
[0055]
The column structure 22a of the metal oxide film 22 tends to become more acicular or finer because the metal oxide film 22 is formed on the fine column structure of the metal oxide film 21. The column structure 22a of the metal oxide film 22 is considered to be grown on the column structure of the metal oxide film 21.
[0056]
In the formation of the auxiliary layer 20, instead of the above-described method, before the metal film formed in the first metal film forming step is oxidized, the auxiliary layer 20 is further formed on the metal film in the second metal film forming step. The metal films may be laminated and then these two metal films may be oxidized in a single oxidation step. The metal material used in each metal film formation step and the oxidation method in the oxidation step are the same as those described above. Also by such a technique, the auxiliary layer 20 composed of the metal oxide film 21 and the metal oxide film 22 having a fine column structure 22a can be formed.
[0057]
In the manufacture of the magneto-optical recording medium X2, next, on the auxiliary layer 20 formed in this manner, the magnetic portion 11, the dielectric layer 14, and the like, as described above with respect to the first embodiment, And the heat dissipation layer 15 is formed sequentially. In this way, the magneto-optical recording medium X2 can be manufactured.
[0058]
In the magneto-optical recording medium X2, the auxiliary layer 20 provided as a base film for the magnetic part 11 including the recording layer has a column structure 22a for increasing the perpendicular magnetic anisotropy of the magnetic part 11 and thus the recording layer. And has sufficient light transmittance. Therefore, according to the magneto-optical recording medium X2, similarly to the magneto-optical recording medium X1, a high recording density can be appropriately achieved.
[0059]
In addition, in the magneto-optical recording medium X2, since the metal oxide film 22 is laminated on the column structure of the metal oxide film 21, the column structure 22a of the metal oxide film 22 or the auxiliary layer 20 has a fine structure. It tends to become. The finer the column structure 22a, the higher the perpendicular magnetic anisotropy of the magnetic part 11 formed on the stacked structure.
[0060]
Such a magneto-optical recording medium X2 is particularly useful when implemented as an MSR, MAMMOS, or DWDD magneto-optical disk having excellent reproduction resolution.
[0061]
[Example 1]
A magneto-optical recording medium of this example was manufactured as a magneto-optical disk having the laminated structure shown in FIG. In the magneto-optical recording medium of this embodiment, the magnetic part is composed of a single recording layer.
[0062]
In the production of the magneto-optical recording medium of this example, first, SiN is formed on a magneto-optical disk substrate (made of polycarbonate) by a DC magnetron sputtering method using a DC magnetron sputtering apparatus until the thickness becomes 75 nm. Was formed into a dielectric layer. Specifically, SiN was formed on the substrate by reactive sputtering performed using an Si target and using Ar gas and N ₂ gas as sputtering gas. The substrate has predetermined lands and grooves on the dielectric layer lamination surface. In this sputtering, the flow ratio of Ar gas and N ₂ gas was 2: 1, the sputtering gas pressure was 0.3 Pa, and the sputtering power was 0.5 kW. Subsequent film formation was also carried out by DC magnetron sputtering using the same apparatus.
[0063]
Next, a metal film for forming an auxiliary layer was formed on the dielectric layer by depositing Ag to a thickness of 0.5 nm. In this sputtering, an Ag target was used, Ar gas was used as the sputtering gas, the sputtering gas pressure was 0.1 Pa, and the sputtering power was 0.5 kW.
[0064]
Next, the metal film formed as described above was oxidized. Specifically, after introducing O ₂ gas into the sputtering chamber of the DC magnetron sputtering apparatus after forming the metal film, the metal film was allowed to stand for 3 minutes under the condition of a gas pressure of 1 Pa. It has been confirmed that the metal film can be oxidized by allowing the metal film to stand for 10 minutes under the condition of a gas pressure of 1 Pa after introducing the O ₂ gas. It has also been confirmed that the metal film can be oxidized by leaving the metal film in the chamber for 10 minutes at a substrate temperature of 80 ° C. without introducing O ₂ gas. In addition, it has been confirmed that the oxidation of the metal film can be performed by oxygen plasma etching. In this case, for example, the oxygen gas pressure in the chamber is 0.5 Pa, and the etching time is 20 seconds.
[0065]
In the production of the magneto-optical recording medium of this example, a recording layer was then formed by depositing a TbFeCо amorphous alloy (Tb ₂₀ Fe ₇₀ Cо ₁₀ ) on the auxiliary layer until the thickness reached 25 nm. . In this sputtering, a TbFeCо alloy target was used, Ar gas was used as the sputtering gas, the sputtering gas pressure was 0.5 Pa, and the sputtering power was 0.5 kW. The Curie temperature of the formed Tb ₂₀ Fe ₇₀ CO ₁₀ recording layer was about 200 ° C.
[0066]
Next, a dielectric layer was formed by depositing SiN on the recording layer to a thickness of 15 nm. The specific conditions are the same as described above with respect to the formation of the SiN dielectric layer described above in this embodiment.
[0067]
Next, a heat dissipation layer was formed by depositing Ag on the dielectric layer until the thickness reached 30 nm. In this sputtering, an Ag target was used, Ar gas was used as the sputtering gas, the sputtering gas pressure was 0.1 Pa, and the sputtering power was 0.5 kW. As described above, the magneto-optical recording medium of this example was produced.
[0068]
[Examples 2 to 7]
The metal film for forming the auxiliary layer is replaced with the film formation of Ag, Al (Example 2), Ni (Example 3), Ti (Example 4), Zr (Example 5), Y (Example 6) ) Or Ru (Example 7), and the same conditions as in Example 1 except that the conditions (gas pressure and standing time) according to each metal film were changed in the subsequent oxidation treatment. From the formation of the dielectric layer (SiN, thickness 75 nm) to the formation of the heat dissipation layer (Ag, thickness 30 nm), the magneto-optical recording medium of each example was manufactured.
[0069]
Example 8
A magneto-optical recording medium of this example was manufactured as a magneto-optical disk having the laminated structure shown in FIG. In the magneto-optical recording medium of this example, the magnetic part has a two-layer structure including a recording layer and a reproducing layer.
[0070]
In the production of the magneto-optical recording medium of this example, first, as in Example 1, a dielectric layer (SiN, thickness 75 nm) and an auxiliary layer (silver oxide, thickness) are formed on the magneto-optical disk substrate. 0.5 nm) were sequentially formed.
[0071]
Next, a reproduction layer was formed by depositing a GdFeCо amorphous alloy (Gd ₂₂ Fe ₅₈ Cо ₂₀ ) on the auxiliary layer to a thickness of 7 nm. In this sputtering, a GdFeCо alloy target was used, Ar gas was used as the sputtering gas, the sputtering gas pressure was 0.5 Pa, and the sputtering power was 0.5 kW.
[0072]
Next, a recording layer was formed by depositing a TbFeCо amorphous alloy (Tb ₂₀ Fe ₇₀ Cо ₁₀ ) on the reproducing layer to a thickness of 18 nm. In this sputtering, a TbFeCо alloy target was used, Ar gas was used as the sputtering gas, the sputtering gas pressure was 0.5 Pa, and the sputtering power was 0.5 kW. The Curie temperature of the formed Tb ₂₀ Fe ₇₀ CO ₁₀ recording layer was about 200 ° C.
[0073]
Next, as in Example 1, a dielectric layer (SiN, thickness 15 nm) and a heat dissipation layer (Ag, thickness 30 nm) were sequentially formed on the recording layer. As described above, the magneto-optical recording medium of this example was produced. In the magneto-optical recording medium of the present example, the recording layer has a larger perpendicular coercivity than the reproducing layer, and the reproducing layer has a Kerr rotation angle in the reproducing laser larger than that of the recording layer.
[0074]
Example 9
A magneto-optical recording medium of this example was manufactured as an MSR type magneto-optical disk having the laminated structure shown in FIG. In the magneto-optical recording medium of the present embodiment, the magnetic part has a three-layer structure including a recording layer, a reproducing layer, and an intermediate layer between them in order to realize MSR reproduction.
[0075]
In the production of the magneto-optical recording medium of this example, first, as in Example 1, a dielectric layer (SiN, thickness 75 nm) and an auxiliary layer (silver oxide, thickness) are formed on the magneto-optical disk substrate. 0.5 nm) were sequentially formed.
[0076]
Next, a reproduction layer was formed by depositing a GdFeCо amorphous alloy (Gd ₂₅ Fe ₆₂ Co ₁₃ ) on the auxiliary layer to a thickness of 40 nm. In this sputtering, a GdFeCо alloy target was used, Ar gas was used as the sputtering gas, the sputtering gas pressure was 0.5 Pa, and the sputtering power was 0.5 kW. The Curie temperature of the formed Gd ₂₅ Fe ₆₂ Co ₁₃ reproducing layer was about 300 ° C.
[0077]
Next, an intermediate layer was formed by depositing a GdFe amorphous alloy (Gd ₃₁ Fe ₆₉ ) on the reproducing layer until the thickness reached 40 nm. In this sputtering, a GdFe alloy target was used, Ar gas was used as the sputtering gas, the sputtering gas pressure was 0.5 Pa, and the sputtering power was 0.5 kW. The Curie temperature of the formed Gd ₃₁ Fe ₆₉ intermediate layer was about 220 ° C.
[0078]
Next, a recording layer was formed by depositing a TbFeCo amorphous alloy (Tb ₂₄ Fe ₅₉ Co ₁₇ ) on the intermediate layer until the thickness reached 50 nm. In this sputtering, a TbFeCo alloy target was used, Ar gas was used as the sputtering gas, the sputtering gas pressure was 0.5 Pa, and the sputtering power was 0.5 kW. The Curie temperature of the formed Tb ₂₄ Fe ₅₉ Co ₁₇ recording layer was about 280 ° C.
[0079]
Next, as in Example 1, a dielectric layer (SiN, thickness 15 nm) and a heat dissipation layer (Ag, thickness 30 nm) were sequentially formed on the recording layer. As described above, the magneto-optical recording medium of this example was produced. In the magneto-optical recording medium of this example, the recording layer has a higher perpendicular coercivity than the reproducing layer, the reproducing layer has a larger Kerr rotation angle in the reproducing laser than the recording layer, and the intermediate layer has a Curie temperature higher than the other layers. Is low.
[0080]
Example 10
A magneto-optical recording medium of this example was manufactured as a MAMMOS type magneto-optical disk having the laminated structure shown in FIG. In the magneto-optical recording medium of the present embodiment, the magnetic part has a three-layer structure including a recording layer, a reproducing layer, and an intermediate layer between them in order to realize MAMMOS reproduction.
[0081]
In the production of the magneto-optical recording medium of this example, first, as in Example 1, a dielectric layer (SiN, thickness 75 nm) and an auxiliary layer (silver oxide, thickness) are formed on the magneto-optical disk substrate. 0.5 nm) were sequentially formed.
[0082]
Next, a reproducing layer of this example was formed by forming a GdFeCо amorphous alloy (Gd ₂₇ Fe ₆₂ Co ₁₁ ) on the auxiliary layer until the thickness reached 30 nm. In this sputtering, a GdFeCо alloy target was used, Ar gas was used as the sputtering gas, the sputtering gas pressure was 0.5 Pa, and the sputtering power was 0.5 kW. The Curie temperature of the formed Gd ₂₇ Fe ₆₂ Co ₁₁ reproducing layer was about 240 ° C.
[0083]
Next, an intermediate layer of this example was formed by depositing a TbFeCo amorphous alloy (Tb ₂₀ Fe ₇₉ Co ₁ ) on the reproduction layer until the thickness reached 10 nm. In this sputtering, a TbFeCo alloy target was used, Ar gas was used as the sputtering gas, the sputtering gas pressure was 0.5 Pa, and the sputtering power was 0.5 kW. The Curie temperature of the formed Tb ₂₀ Fe ₇₉ Co ₁ intermediate layer was about 130 ° C.
[0084]
Next, a TbFeCo amorphous alloy (Tb ₂₇ Fe ₅₇ Co ₁₆ ) was formed on the intermediate layer to a thickness of 60 nm, thereby forming the recording layer of this example. In this sputtering, a TbFeCo alloy target was used, Ar gas was used as the sputtering gas, the sputtering gas pressure was 0.5 Pa, and the sputtering power was 0.5 kW. The Curie temperature of the formed Tb ₂₇ Fe ₅₇ Co ₁₆ recording layer was about 260 ° C.
[0085]
Next, as in Example 1, a dielectric layer (SiN, thickness 15 nm) and a heat dissipation layer (Ag, thickness 30 nm) were sequentially formed on the recording layer. As described above, the magneto-optical recording medium of this example was produced. In the magneto-optical recording medium of this example, the recording layer has a higher perpendicular coercivity than the reproducing layer, the reproducing layer has a larger Kerr rotation angle in the reproducing laser than the recording layer, and the intermediate layer has a Curie temperature higher than the other layers. Is low.
[0086]
Example 11
A magneto-optical recording medium of this example was manufactured as a MAMMOS type magneto-optical disk having the laminated structure shown in FIG. In the magneto-optical recording medium of the present embodiment, the magnetic part has a three-layer structure including a recording layer, a reproducing layer, and an intermediate layer between them in order to realize MAMMOS reproduction.
[0087]
In the production of the magneto-optical recording medium of this example, first, similarly to Example 1, a dielectric layer (SiN, thickness 75 nm) was formed on the magneto-optical disk substrate.
[0088]
Next, a first metal film was formed by depositing Ag on the dielectric layer to a thickness of 0.5 nm. In this sputtering, an Ag target was used, Ar gas was used as the sputtering gas, the sputtering gas pressure was 0.1 Pa, and the sputtering power was 0.5 kW.
[0089]
Next, a second metal film was formed by depositing Ru on the first metal film to a thickness of 0.5 nm. In this sputtering, a Ru target was used, Ar gas was used as the sputtering gas, the sputtering gas pressure was 0.2 Pa, and the sputtering power was 0.5 kW.
[0090]
Next, the first and second metal films formed as described above were oxidized. Specifically, after introducing O ₂ gas into the sputtering chamber of the DC magnetron sputtering apparatus after forming the metal film, the metal film was allowed to stand for 15 minutes under a gas pressure of 1 Pa. In this manner, the auxiliary layer of this example having a laminated structure composed of the first metal oxide film and the second metal oxide film was formed.
[0091]
Next, on the auxiliary layer, in the same manner as in Example 10, the reproducing layer (Gd ₂₇ Fe ₆₂ Co ₁₁ , thickness 30 nm), the intermediate layer (Tb ₂₀ Fe ₇₉ Co ₁ , thickness 10 nm), and the recording layer (Tb ₂₇ Fe ₅₇ Co ₁₆ , thickness 60 nm), dielectric layer (SiN, thickness 15 nm), and heat dissipation layer (Ag, thickness 30 nm) were sequentially formed. As described above, the magneto-optical recording medium of this example was produced. In the magneto-optical recording medium of this example, the recording layer has a higher perpendicular coercivity than the reproducing layer, the reproducing layer has a larger Kerr rotation angle in the reproducing laser than the recording layer, and the intermediate layer has a Curie temperature higher than the other layers. Is low.
[0092]
[Examples 12 to 21]
The thickness of the auxiliary layer (thickness of the metal film for forming the auxiliary layer) is changed to 0.5 nm, 0.1 nm (Example 12), 0.2 nm (Example 13), 0.7 nm (Example 14) ), 1.0 nm (Example 15), 1.5 nm (Example 16), 2.0 nm (Example 17), 3.0 nm (Example 18), 4.0 nm (Example 19), 5.0 nm Except for (Example 20) or 6.0 nm (Example 21), the formation of the dielectric layer (SiN, thickness 75 nm) to the formation of the heat dissipation layer (Ag, thickness 30 nm) are the same as in Example 1. Thus, the magneto-optical recording medium of each example was manufactured.
[0093]
[Comparative Example 1]
A magneto-optical recording medium of this comparative example was manufactured as a magneto-optical disk having the laminated structure shown in FIG. Specifically, from the formation of the dielectric layer (SiN, thickness 75 nm) as in Example 1, except that the formation of the metal film for forming the auxiliary layer and the subsequent oxidation treatment were not performed, the heat dissipation layer ( The magneto-optical recording medium of this comparative example was manufactured by performing the process up to the formation of (Ag, thickness 30 nm).
[0094]
[Comparative Examples 2 to 4]
A dielectric layer (SiN, thickness 75 nm) was formed in the same manner as in Example 8, Example 9, and Example 10 except that the formation of the metal film for forming the auxiliary layer and the subsequent oxidation treatment were not performed. The magneto-optical recording media of Comparative Example 2, Comparative Example 3, and Comparative Example 4 were produced by performing the formation to the formation of the heat dissipation layer (Ag, thickness 30 nm). Therefore, the magneto-optical recording medium of Comparative Example 2 has a laminated structure in which the auxiliary layer is removed from the magneto-optical recording medium of Example 8. Similarly, each magneto-optical recording medium of Comparative Examples 3 and 4 has a laminated structure in which the auxiliary layer is removed from the corresponding magneto-optical recording medium of Examples 9 and 10.
[0095]
[Observation of auxiliary layer surface]
During the medium preparation process of Example 1, before forming the recording layer on the auxiliary layer, the surface of the auxiliary layer was observed using an atomic force microscope (manufactured by Seiko Instruments). The surface shape obtained by observation is schematically shown in FIG. In FIG. 10, the cross section of the auxiliary layer is hatched. A plurality of needle-like columns were formed on the surface of the auxiliary layer. The average surface roughness Ra of the auxiliary layer in Example 1 was 0.3 nm, and the average diameter of the column was 12 nm. The average diameter was determined by taking the diameter at the half height of the column as the diameter of each column. These results are listed in the table of FIG.
[0096]
During the medium production process in Examples 2 to 7 and 11, the auxiliary layer surface was observed in the same manner as in Example 1 before forming the magnetic part on the auxiliary layer. For the auxiliary layer in each example, the average surface roughness Ra and column average diameter obtained by observation are listed in the table of FIG.
[0097]
It has been confirmed that the column structure of the auxiliary layer in each example is substantially maintained on the exposed surface of the magnetic part (recording layer) formed on the auxiliary layer.
[0098]
During the medium production process in Comparative Example 1, the surface of the dielectric layer was observed in the same manner as in Example 1 before forming the recording layer on the dielectric layer. The surface shape obtained by observation is schematically shown in FIG. In FIG. 11, the cross section of the surface of the dielectric layer is indicated by the same scale as FIG. 10 with hatching. In this comparative example, the average surface roughness Ra of the dielectric layer was 0.9 nm. When each convex shape was regarded as a column, the average diameter of the column was 53 nm. These results are listed in the table of FIG.
[0099]
From the comparison between FIG. 10 and FIG. 11, it can be seen that the column structure on the surface of the auxiliary layer in Example 1 is more acicular or finer than the uneven shape on the surface of the dielectric layer in Comparative Example 1.
[0100]
From the table of FIG. 12, it can be seen that the column structure on the surface of the auxiliary layer in Examples 1 to 7 and 11 is finer than the uneven shape on the surface of the dielectric layer in Comparative Example 1.
[0101]
(Characteristic evaluation)
The recording / reproducing characteristics of the magneto-optical recording media of Examples 1, 8 to 11 and Comparative Examples 1 to 5 were examined.
[0102]
For the magneto-optical recording medium of Example 1, first, a predetermined mark is passed through a sufficiently long space (space length: 2.0 μm) with respect to the information track in the magneto-optical recording medium (magneto-optical disk) of Example 1. A long recording mark was repeatedly recorded. The recording process was performed by a light modulation recording method using a read / write tester. The numerical aperture NA of the objective lens of this tester is 0.6, and the laser wavelength is 650 nm. In the recording process, the power of the recording laser was appropriately changed, the laser scanning speed was 6 m / s, and the applied magnetic field was 150 Oe. Next, the magneto-optical recording medium was reproduced, and the carrier level (C level) of the reproduction signal having the maximum intensity was measured. The reproduction process was performed using the same read / write tester, the laser power was 1.5 mW, the laser scanning speed was 6 m / s, and the applied magnetic field was 0 Oe. The C level of the reproduced signal was measured using a spectrum analyzer. Such recording processing and reproduction processing were performed for each mark length by changing the mark length of the recording mark. On the other hand, the recording / reproducing characteristics of the magneto-optical recording medium of Comparative Example 1 were examined under the same conditions. The result of the characteristic evaluation of each magneto-optical recording medium of Example 1 and Comparative Example 1 is shown in the graph of FIG. In the graph of FIG. 13, the horizontal axis represents the mark length, and the vertical axis represents the change from the C level when the mark length is sufficiently long. The same applies to the graphs of FIGS. 14 to 17 described later.
[0103]
For the magneto-optical recording media of Example 8 and Comparative Example 2, the recording / reproducing characteristics were examined in the same manner as the magneto-optical recording medium of Example 1. The result of the characteristic evaluation of each magneto-optical recording medium of Example 8 and Comparative Example 2 is shown in the graph of FIG.
[0104]
For the magneto-optical recording medium of Example 9, first, a recording mark having a predetermined mark length was repeatedly recorded on the information track in the magneto-optical recording medium of Example 9. The recording process was performed by the light modulation recording method using the same read / write tester as used in Example 1. In the recording process, the power of the recording laser was appropriately changed, the laser scanning speed was 6 m / s, and the applied magnetic field was 300 Oe. Next, the magneto-optical recording medium was reproduced using the same read / write tester, and the C level of the reproduced signal was measured. In the reproduction process, the laser power was 2.7 mW, the laser scanning speed was 6 m / s, and the applied magnetic field was 300 Oe. The C level of the reproduced signal was measured using a spectrum analyzer. Such recording processing and reproduction processing were performed for each mark length by changing the mark length of the recording mark. The magneto-optical recording medium of Comparative Example 3 was also examined for recording / reproducing characteristics under the same conditions. The result of the characteristic evaluation of each magneto-optical recording medium of Example 9 and Comparative Example 3 is shown in the graph of FIG.
[0105]
For the magneto-optical recording medium of Example 10, first, a recording mark having a predetermined mark length was repeatedly recorded on the information track in the magneto-optical recording medium of Example 10. The recording process was performed by a laser strobe magnetic field recording method using the same read / write tester as used in Example 1. In the recording process, the power of the recording laser was 10 mW, the laser scanning speed was 6 m / s, and the applied magnetic field was 250 Oe. Next, the magneto-optical recording medium was reproduced using the same read / write tester, and the C level of the reproduced signal was measured. In the reproduction process, the laser power was 2.2 mW, the laser scanning speed was 6 m / s, and the applied magnetic field was 0 Oe. The C level of the reproduced signal was measured using a spectrum analyzer. Such recording processing and reproduction processing were performed for each mark length by changing the mark length of the recording mark. The magneto-optical recording medium of Comparative Example 4 was also examined for recording / reproducing characteristics under the same conditions. The result of the characteristic evaluation of each magneto-optical recording medium of Example 10 and Comparative Example 4 is shown in the graph of FIG.
[0106]
For the magneto-optical recording medium of Example 11, the recording / reproducing characteristics were examined under the same conditions as for the magneto-optical recording medium of Example 10. The result of the characteristic evaluation of the magneto-optical recording medium of Example 11 is shown in the graph of FIG. 17 together with the result of Comparative Example 4.
[0107]
As shown in the graphs of FIGS. 13 to 17, when reproducing a recording mark having a short mark length, the magneto-optical recording medium according to the embodiment of the present invention has the same stacked structure except that it does not have an auxiliary layer. The C level is higher than that of the magneto-optical recording medium according to the comparative example. Therefore, it can be seen that the magneto-optical recording media of Examples 1 and 8 to 11 are more advantageous for stably recording recording marks having a shorter mark length than the corresponding magneto-optical recording media of Comparative Examples 1 to 4. .
[0108]
[Dependence of column structure on auxiliary layer thickness]
Before forming the recording layer on the auxiliary layer during the medium preparation process of Examples 12 to 21 having different auxiliary layer thicknesses, the surface of the auxiliary layer was formed using an atomic force microscope (manufactured by Seiko Instruments). The average surface roughness Ra and the average column diameter of each auxiliary layer were observed. The result is shown in the graph of FIG. In the graph, the horizontal axis represents the auxiliary layer thickness, the left vertical axis represents the average surface roughness Ra, and the right vertical axis represents the average column diameter. The two plots at the auxiliary layer thickness of 0 nm correspond to the data for Comparative Example 1 listed in the table of FIG. In the graph of FIG. 18, the line 31 represents the dependence of the average surface roughness Ra on the auxiliary layer thickness, and the line 32 represents the dependence of the average column diameter on the auxiliary layer thickness.
[0109]
As shown in the graph of FIG. 18, the average surface roughness Ra and the column diameter both suddenly decrease when the auxiliary layer thickness is between 0.1 nm and 0.2 nm, and the auxiliary layer thickness is 0.2 nm. Both are small enough. In addition, when the auxiliary layer thickness exceeds 5 nm, the column diameter is particularly significantly increased. Thus, it can be seen from the graph of FIG. 18 that the column structure on the surface of the auxiliary layer is fine when the auxiliary layer thickness is in the range of 0.2 to 5.0 nm. Therefore, in the present invention, it can be understood that the auxiliary layer thickness is preferably in the range of 0.2 to 5.0 nm.
[Brief description of the drawings]
[Figure 1]
1 is a partial cross-sectional schematic diagram of a magneto-optical recording medium according to a first embodiment of the present invention.
[Figure 2]
1 illustrates a laminated configuration of a magneto-optical recording medium according to the present invention.
[Fig. 3]
It is a partial cross-sectional schematic diagram of the magneto-optical recording medium based on the 2nd Embodiment of this invention.
[Fig. 4]
1 illustrates a laminated configuration of a magneto-optical recording medium of Example 1.
[Figure 5]
8 shows a stacked configuration of a magneto-optical recording medium of Example 8.
[Fig. 6]
10 shows a stacked structure of a magneto-optical recording medium of Example 9.
[Fig. 7]
2 illustrates a stacked configuration of a magneto-optical recording medium according to Example 10.
[Fig. 8]
2 shows a stacked structure of a magneto-optical recording medium of Example 11.
FIG. 9
2 shows a laminated structure of a magneto-optical recording medium of Comparative Example 1.
FIG. 10
5 is an enlarged schematic cross-sectional view of the vicinity of the auxiliary layer surface in Example 1. FIG.
FIG. 11
4 is an enlarged schematic cross-sectional view of the vicinity of a dielectric layer surface in Comparative Example 1. FIG.
FIG.
4 is a table in which average surface roughness Ra and average column diameter in the auxiliary layers of Examples 1 to 7 and 11 and the dielectric layer of Comparative Example 1 are listed.
FIG. 13
The result of the characteristic evaluation in Example 1 and Comparative Example 1 is represented.
FIG. 14
The result of the characteristic evaluation in Example 8 and Comparative Example 2 is represented.
FIG. 15
The result of the characteristic evaluation in Example 9 and Comparative Example 3 is represented.
FIG. 16
The result of the characteristic evaluation in Example 10 and Comparative Example 4 is represented.
FIG. 17
The result of the characteristic evaluation in Example 11 and Comparative Example 4 is represented.
FIG. 18
Regarding the auxiliary layer, it represents the thickness dependency of the average surface roughness Ra and the thickness dependency of the average column diameter.

Claims (20)

A substrate having optical transparency;
A magnetic part for recording and reproducing functions;
An auxiliary layer having a column structure surface interposed between the base material and the magnetic part to have optical transparency and to increase perpendicular magnetic anisotropy of the magnetic part in contact with the magnetic part; A magneto-optical recording medium. The magneto-optical recording medium according to claim 1, wherein the column structure surface has a plurality of columns, and the average diameter of the plurality of columns is 5 to 35 nm. The magneto-optical recording medium according to claim 2, wherein the column structure surface has an average surface roughness of 0.6 nm or less. The magneto-optical recording medium according to claim 1, wherein the auxiliary layer is made of a metal oxide. The metal oxide is an oxide of a metal selected from the group consisting of Ag, Al, Ni, Ti, Zr, Y, and Ru, or Ag, Al, Ni, Ti, Zr, Y, and Ru. The magneto-optical recording medium according to claim 4, which is an oxide of an alloy containing a metal selected from the group. The magneto-optical recording medium according to claim 1, wherein the auxiliary layer has a thickness of 0.2 to 5 nm. The magneto-optical recording medium according to claim 1, wherein the auxiliary layer is composed of two or more metal oxide films. The magneto-optical recording medium according to claim 1, wherein the magnetic part has a multilayer structure including a recording layer having a recording function and a reproducing layer having a reproducing function. The magneto-optical recording medium according to claim 8, wherein the reproducing layer is in contact with the column structure surface. The magneto-optical recording medium according to claim 8, wherein the magnetic part has a multilayer structure for realizing an MSR method, a MAMMOS method, or a DWDD method. A light-transmitting base material; a magnetic part responsible for a recording function and a reproducing function; and a light-transmitting material interposed between the base material and the magnetic part and in contact with the magnetic part. A method for manufacturing a magneto-optical recording medium comprising an auxiliary layer having a column structure surface for increasing the perpendicular magnetic anisotropy of a portion,
Forming a metal film on the substrate;
An oxidation step for forming the auxiliary layer by oxidizing the metal film;
Forming the magnetic part by depositing a magnetic material on the auxiliary layer. The method for manufacturing a magneto-optical recording medium according to claim 11, wherein in the oxidation step, the metal film is exposed to an oxygen atmosphere. The method of manufacturing a magneto-optical recording medium according to claim 11, wherein the metal film is heated in the oxidation step. 12. The method of manufacturing a magneto-optical recording medium according to claim 11, wherein the metal film is subjected to oxygen plasma etching in the oxidation step. The metal film is selected from a single metal selected from the group consisting of Ag, Al, Ni, Ti, Zr, Y, and Ru, or from a group consisting of Ag, Al, Ni, Ti, Zr, Y, and Ru. The method for producing a magneto-optical recording medium according to claim 11, which is an alloy containing two or more metals. A light-transmitting base material; a magnetic part responsible for a recording function and a reproducing function; and a light-transmitting material interposed between the base material and the magnetic part and in contact with the magnetic part. A method for manufacturing a magneto-optical recording medium comprising an auxiliary layer having a column structure surface for increasing the perpendicular magnetic anisotropy of a portion,
Forming a first metal film on the substrate;
A first oxidation step for forming a first metal oxide film by oxidizing the first metal film;
Forming a second metal film on the first metal oxide film;
A second oxidation step for forming the auxiliary layer by oxidizing the second metal film to form a second metal oxide film;
Forming the magnetic part by depositing a magnetic material on the auxiliary layer. 17. The method of manufacturing a magneto-optical recording medium according to claim 16, wherein in the first oxidation step and / or the second oxidation step, the first metal film and / or the second metal film are exposed to an oxygen atmosphere. 17. The method of manufacturing a magneto-optical recording medium according to claim 16, wherein in the first oxidation step and / or the second oxidation step, the first metal film and / or the second metal film are heated. 17. The magneto-optical recording medium manufacturing according to claim 16, wherein in the first oxidation step and / or the second oxidation step, oxygen plasma etching is performed on the first metal film and / or the second metal film. Method. A light-transmitting base material; a magnetic part responsible for a recording function and a reproducing function; and a light-transmitting material interposed between the base material and the magnetic part and in contact with the magnetic part. A method for manufacturing a magneto-optical recording medium comprising an auxiliary layer having a column structure surface for increasing the perpendicular magnetic anisotropy of a portion,
Forming a first metal film on the substrate;
Forming a second metal film on the first metal film;
Forming the auxiliary layer by oxidizing the first metal film and the second metal film;
Forming the magnetic part by depositing a magnetic material on the auxiliary layer.

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