JP2701337B2 - Magneto-optical recording medium - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium for recording / reproducing information using a laser beam or the like by utilizing a magneto-optical effect, and in particular, to suppress corrosion and pitting corrosion. The present invention relates to a magneto-optical recording medium capable of stably maintaining magneto-optical characteristics while maintaining stability.

[Summary of the Invention]

The present invention provides an artificial lattice film in which a Co layer and a Pt layer and / or a Pd layer are alternately laminated as a recording layer, and the recording layer is formed on a substrate via a dielectric underlayer to prevent corrosion and pitting. An object of the present invention is to provide a magneto-optical recording medium having good magneto-optical characteristics while suppressing eclipse.

[Conventional technology]

In recent years, as a rewritable high-density recording system, a magneto-optical recording system that performs recording and reproduction using a semiconductor laser beam or the like has attracted attention.

As a recording material used in this magneto-optical recording method,
An amorphous alloy combining rare earth elements such as Cd, Tb, and Dy with transition elements such as Fe and Co has been a typical example of the related art. But,
Rare earth elements and Fe constituting these amorphous alloys are very easily oxidized, and have a property of easily binding to oxygen in the air to form oxides. When such oxidation progresses and leads to corrosion or pitting, the loss of signal is induced. In particular, when the rare earth element undergoes selective oxidation, the C / N ratio decreases with the decrease in the coercive force and the remanent magnetic Kerr rotation angle. Is deteriorated. Such a problem cannot be avoided as long as a rare earth element is used.

The corrosion and pitting described above cause T
It can be prevented by adding an element that can form a passive film such as i, Cr, or Al, or an inert element such as Pt, Pd, or Co.The effect is confirmed when the layer is relatively thick. ing. However, the use of such additional elements often leads to a decrease in the magnetic Kerr rotation angle,
(4) Since the desired effect cannot be obtained with the layer thickness below, there is a problem that a protective film or the like must be used in combination.

On the other hand, the present applicant has previously disclosed Co-Pd in which a Co layer and a Pt layer and / or a Pd layer are alternately stacked without using a rare earth element.
It is disclosed that an artificial lattice film of a Co, Pt-based or Co-Pd-Pt-based material exhibits excellent corrosion resistance and has excellent magneto-optical properties in a thin metal region.

[Problems to be solved by the invention]

By the way, in order to put the magneto-optical recording medium into practical use in the future, not only the above-mentioned increase in the magnetic Kerr rotation angle but also an improvement in coercive force and an improvement in the squareness and squareness ratio of the magnetic Kerr curve are essential elements. Here, the squareness ratio is the ratio between the residual magnetic Kerr rotation angle theta _k ^r a saturated magnetic Kerr rotation angle theta _k ^s, the value is good closer to 1. In particular, in recent studies, the squareness and squareness ratio are closely related to the uniaxial anisotropy energy of the recording layer. It has been clarified that the shape of the write bit is sharpened by the decrease, and the C / N ratio at the time of reading is improved.

Co-Pd system, Co-Pt system, Co-Pd disclosed by the applicant earlier.
There is still room for improvement in the magneto-optical characteristics as described above for the -Pt-based signal grating film.

Therefore, an object of the present invention is to provide a magneto-optical recording medium having a recording layer in which a Co layer and a Pd layer and / or a Pt layer are alternately laminated, and having excellent coercive force and squareness of a magnetic Kerr curve and an excellent squareness ratio. I do.

[Means for solving the problem]

The magneto-optical recording medium according to the present invention has been proposed in order to achieve the above-mentioned object. An artificial lattice film in which Co layers and Pt layers and / or Pd layers are alternately laminated is used as a recording layer. The recording layer is formed on a substrate via a dielectric underlayer.

First, the artificial lattice film that can be used as a recording layer in the magneto-optical recording medium according to the present invention has a Co layer and a Pt layer laminated.
Co-Pt-based artificial lattice film, Co-Pd-based artificial lattice film in which a Co layer and a Pd layer are laminated, or a laminate of a Co layer and a Pt-Pd alloy layer or a Co layer, a Pt layer, and a Pd layer Is a Co-Pt-Pd-based artificial lattice film in which is laminated.

In any case, the total thickness of the artificial lattice film serving as the recording layer is
Preferably, it is in the range of 50 to 800 °. This is due to the fact that the magnetic car rotation angle and coercive force will deteriorate if it goes out of the range of
This is because a decrease in magneto-optical characteristics is observed.

In particular, in the case of a Co-Pt-based artificial lattice film, the Co layer is 2 to 8２〜,
More preferably, the Pt layer has a thickness of 3 to 40 ° and a total thickness of 50 to 400 °, and exhibits good magneto-optical characteristics in such a range. Of course, magneto-optical properties are exhibited in other ranges, but the total thickness is
If it exceeds 400 °, the squareness ratio tends to decrease slightly.

Similarly, in the case of a Co—Pd-based artificial lattice film, Co layers 1 to 9
Å, Pd layer 2２〜40Å, total thickness 50〜800Å exhibit good magneto-optical properties.

The above range of the layer thickness is set from the viewpoint of optimizing the magneto-optical characteristics. In any case, outside the above-mentioned range, an in-plane magnetization component is generated and the magneto-optical characteristics deteriorate.

The interface between the metal layers constituting the above-described artificial lattice film is ideally formed so as to have a so-called superlattice structure in which dissimilar metal atoms do not disturb each other and have a so-called superlattice structure. May have a so-called modulation structure (composition modulation structure) in which the composition fluctuates while maintaining a fixed period as a whole while causing the above.

The artificial lattice film can be formed by sputtering, vacuum deposition, or molecular beam epitaxy (MBE).

The artificial lattice film has B, C, Al, Si, P, Ti, V, Cr, Mn, Fe, Ni, C for the purpose of lowering the Curie point and improving thermal stability.
u, Zn, Ga, Ge, Zr, Nb, Mo, Ru, Rh, Ag, In, Sn, Hf, Ta, W, Re, Os, I
At least one of r, Au, Pb, Bi and rare earth elements may be appropriately added.

In the magneto-optical recording medium according to the present invention, prior to forming the recording layer as described above, a dielectric base film is first formed on a suitable substrate such as glass by sputtering, vacuum deposition, MBE, or the like. The thickness of the dielectric base film is selected in the range of 5 to 5000 °. If it is smaller than the above range, the desired effect as the dielectric underlayer cannot be obtained, and if it is larger than the above range, the magneto-optical characteristics may be deteriorated, and also from the viewpoint of productivity and economy. Not practical.

As the material of the above-mentioned dielectric underlayer, Al ₂ O ₃ , Ta ₂ O ₅ , Mg
_{O, SiO 2, TiO 2,} Fe 2 O 3, ZrO 2, Bi 2 O 3, ZrN, TiN, Si
_{3 N 4, AlN, AlSiN,} BN, TaN, NbN can be used. This underlayer has an effect (enhancement effect) of increasing the rotation angle of the magnetic Kerr by an interference effect when an optimum layer thickness is selected.

Further, as the kind of the substrate used in the present invention, a material usually used as a substrate of a magneto-optical recording medium can be used, and typical examples thereof include glass, polycarbonate, PMMA (polymethyl methacrylate) and the like.

FIG. 1 shows a basic configuration of such a magneto-optical recording medium. Here, a recording layer (3) is formed on a substrate (1) via a dielectric base film (2). However, in practice, as shown in FIG.
It is common to provide a metal reflection film (4) of l, Au, Pt, Cu or the like. In order to further improve the magneto-optical characteristics, another dielectric layer (5) is formed on the recording layer (3) as shown in FIG.
May be provided. The material of the derivative layer (5) at this time is
The material may be the same as or different from the material of the above-described derivative base film (2). Alternatively, as shown in FIG. 4, a metal reflection film (4) may be further provided on the dielectric layer (5).

The method of writing on the recording layer of the magneto-optical recording medium having the above-described configuration can supply energy necessary for generating a reversal magnetic domain, such as a needle-shaped magnetic head, a hot pen, and an electron beam, in addition to a light beam. Needless to say, anything can be used.

[Action]

In the magneto-optical recording medium according to the present invention, Co-Pd
By providing a dielectric underlayer between a substrate and a recording layer comprising a Co-Pt-based or Co-Pd-Pt-based artificial lattice film, the perpendicular magnetic anisotropy energy of the recording layer increases.
Thereby, the shape of the write bit is sharpened, and the C / N ratio at the time of reading is improved. Further, when the thickness of the underlayer is optimally selected, an increase in the magnetic Kerr rotation angle can be expected. Therefore, high-quality and high-density perpendicular magnetic recording can be performed.

〔Example〕

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

This example first embodiment, through the Si ₃ N ₄ base film on a glass substrate Co
5 is an example of a magneto-optical recording medium on which a Pt-based artificial lattice film is formed.

First, a Si ₃ N ₄ sintered target having a diameter of 100 mm was placed in a chamber, and a glass substrate was placed on a base provided with a water-cooling device facing the target. Next, reactive sputtering was performed at a gas pressure of 2.5 mTorr in an argon gas atmosphere containing 1% of nitrogen gas to form a Si ₃ N ₄ underlayer at various layer pressures.

Next, Co and Pt targets each having a diameter of 100 mm were set in the same chamber, and the glass substrate on which the Si ₃ N ₄ base film was formed was mounted on a rotating base with a water-cooling device arranged opposite to these targets. The sample was placed and subjected to dual simultaneous magnetron sputtering in an argon gas atmosphere at a gas pressure of 5 mTorr. At this time, DC sputtering (input power: 0.40 A, 300 W) was performed for Co, and high-frequency sputtering (input power: 360 W) was performed for Pt, and the rotation speed of the rotating base was 16 rpm, and the total thickness of the Co-Pt artificial lattice was 100 mm. A membrane was made.

In addition, the period of the created artificial lattice film was obtained from the peak angle in small-angle X-ray scattering.

The magneto-optical characteristics at 780 nm of each magneto-optical recording medium prepared in this manner were evaluated from the glass substrate side using a Kerr curve measuring device. The results are shown in FIGS. 5 (A) and 5 (B). FIG. 5 (A) shows Si ₃ N
_{4 When} the thickness of the underlayer is 550 mm, FIG.
Is equivalent to For comparison, FIG. 5 (C) shows the magneto-optical characteristics of a magneto-optical recording medium similarly prepared without providing a base film. In these figures, the vertical axis is the magnetic car rotation angle θ _k (゜), and the horizontal axis is the intensity H (kOe) of the external magnetic field.
Represents When these figures are compared, it is clear that the coercive force and the squareness are improved when the Si ₃ N ₄ underlayer is provided as compared with the case where the Si ₃ N ₄ underlayer is not provided.

Here, in order to examine the effect of the layer thickness of the Si ₃ N ₄ underlayer on the magneto-optical characteristics in more detail, FIG. 6 shows changes in the coercive force and the magnetic Kerr rotation angle depending on the layer thickness of the Si ₃ N ₄ underlayer. Show. In the figure, the vertical axis indicates coercive force (Oe) or magnetic Kerr rotation angle (゜)
The horizontal axis represents the layer thickness (Å) of the Si ₃ N ₄ underlayer, the black circle (●) plots the coercive force, and the white circle (○) plots the magnetic Kerr rotation angle. Referring to this figure, the coercive force has a layer thickness of 550 corresponding to the case shown in FIG.
It can be seen that the maximum is shown in Å. In addition, the magnetic Kerr rotation angle periodically changes with the thickness of the Si ₃ N ₄ underlayer, and a value between the lowest value and the maximum value in the measured range is 25 degrees.
It can be seen that there is a difference of about%. This indicates that the magnetic Kerr rotation angle can be increased by optimizing the layer thickness.

Second Embodiment This embodiment is an example in which a polycarbonate substrate is used instead of the above-mentioned glass substrate as a substrate in a magneto-optical recording medium similarly using a Si ₃ N ₄ underlayer and a Co—Pt-based artificial lattice film. is there.

This magneto-optical recording medium was prepared as follows. First, reactive sputtering was performed at a gas pressure of 2.5 mTorr in an argon gas atmosphere containing 1% nitrogen gas,
The underlayer of Si ₃ N ₄ was formed on a polycarbonate substrate. Subsequently, in an argon atmosphere with a glass pressure of 5 mTorr, a Co layer was sequentially laminated on the substrate by DC sputtering at a power of 0.3 A and 300 W, and a Pt layer was sequentially laminated by high-frequency sputtering at a power of 360 W to form a Co layer having a total thickness of 100 mm. -A Pt-based artificial lattice film was formed to prepare a magneto-optical recording medium. For comparison, a magneto-optical recording medium without a Si ₃ N ₄ underlayer was similarly prepared.

FIG. 7A and FIG. 7B show magnetic Kerr curves when the magneto-optical characteristics of each of these magneto-optical recording media are measured from the substrate side. FIG. 7A corresponds to the case where a Si ₃ N ₄ underlayer of 700 ° is provided, and FIG. 7B corresponds to the case where no Si ₃ N ₄ underlayer is provided. Comparing these figures, it can be seen that perpendicular magnetic characteristics do not appear on the polycarbonate substrate when no underlayer is provided, and good perpendicular magnetic characteristics appear only when the underlayer is provided.

FIG. 8 shows changes in coercive force and magnetic Kerr rotation angle depending on the thickness of the Si ₃ N ₄ underlayer. In the figure, the vertical axis is the coercive force (Oe)
Alternatively, the abscissa represents the layer thickness (Å) of the Si ₃ N ₄ underlayer, the plot of black circles (●) represents the coercive force, and the plot of white circles (○) represents the squareness ratio. Looking at this figure, the holding force is a layer thickness 700 corresponding to the case shown in FIG.
It can be seen that the maximum is obtained in the layer thickness region near Å. It can also be seen that the squareness ratio shows an almost perfect value in the same layer thickness region, and shows a good value close to 1 in the layer thickness region of 700 ° or more.

Further, FIG. 9 shows a change in the magnetic Kerr rotation angle depending on the thickness of the Si ₃ N ₄ underlayer. In the figure, the vertical axis represents the magnetic Kerr rotation angle (゜), and the horizontal axis represents the layer thickness (Å) of the Si ₃ N ₄ underlayer. Here, as in the case shown in FIG. 6, there is a periodic change in the magnetic Kerr rotation angle with respect to the layer thickness.

Third Embodiment The above is an example of a magneto-optical recording medium using Si ₃ N ₄ as a base film. However, in this embodiment, Co-Pt is formed on a glass substrate via a base film made of another nitride derivative. 1 is an example of a magneto-optical recording medium on which a system artificial lattice film is formed.

The nitride derivatives used in this example were ZrN, BN, AlN and
TiN. A magneto-optical recording medium using these was prepared as follows. First, reactive sputtering is performed at a gas pressure of 2.5 mTorr in an argon gas atmosphere containing 1% nitrogen gas, and a ZrN underlayer, a BN underlayer, or an AlN underlayer of various thicknesses is formed on a glass substrate. Formed.
Subsequently, in an argon atmosphere at a gas pressure of 5 mTorr, a Co layer was applied on each of these glass substrates by direct current sputtering at a power of 0.35 A and 300 V, and a Pt layer was successively laminated by high frequency sputtering at an input power of 380 W to obtain a total thickness. 100Å Co-P
A t-system artificial lattice film was formed to create a magneto-optical recording medium.
For comparison, a magneto-optical recording medium without a base film was similarly prepared.

The magnetic Kerr curves of the magneto-optical characteristics of these magneto-optical recording media measured from the substrate side are shown in FIGS.
It is shown in FIG. FIG. 10 (A) shows a 480 ° ZrN base film,
FIG. 10 (B) shows a 400Å BN undercoat, and FIG. 10 (C) shows a 700Å
FIG. 10 (D) shows a case where no underlying film is provided, which corresponds to the case where an AlN underlying film is provided, respectively. Here, the coercive force when no underlayer is provided is 112 Oe, and the magnetic Kerr rotation angle is 0.61 °. On the other hand, when the underlayer was provided, the coercive force, the squareness, and the rotation angle of the magnetic Kerr were all improved, and particularly when ZrN was used as the underlayer, a remarkable improvement was observed.

FIG. 11 shows the results of examining changes in coercive force and magnetic Kerr rotation angle depending on the thickness of the underlayer when ZrN is used as the underlayer. In the figure, the ordinate represents the coercive force (Oe) or the magnetic Kerr rotation angle (゜), the abscissa represents the layer thickness (Å) of the ZrN underlayer, and the black circle (●) plots the coercive force and the white circle (）). Plots indicate the magnetic car rotation angles, respectively. The figure shows that the coercive force increases with increasing layer thickness.
It can be seen that there is a tendency to saturate around 1000 °, and that the magnetic Kerr rotation angle becomes maximum near the layer thickness of 800 °. The tendency that the magnetic Kerr rotation angle becomes maximum near the layer thickness of 800 ° was also observed when TiN was used as the underlayer under the same conditions as shown in FIG.

Fourth Embodiment In the above embodiments, the case where a Co—Pt-based artificial lattice film is used as a recording layer has been described. However, in this embodiment, a Co—Pd-based artificial lattice film is formed on a glass substrate via a ZrN underlayer. This is an example of a magneto-optical recording medium on which a lattice film is formed.

This magneto-optical recording medium was prepared as follows. First, ZrN underlayers of various thicknesses were formed on a glass substrate according to the direction in the third embodiment described above. Subsequently, in an argon atmosphere with a gas pressure of 11 mTorr, DC sputtering of input power of 0.35 A, 300 V for Co, and high-frequency sputtering of input power of 380 W for Pd were performed, and a Co layer and a Pd layer were formed on each of the above glass substrates. Laminated sequentially, total thickness 10
A 0 ° Co-Pd-based artificial lattice film was formed to prepare a magneto-optical recording medium. For comparison, a magneto-optical recording medium without a base film was similarly prepared.

FIG. 13 (A) and FIG. 13 (A) show the magnetic Kerr curves when the magneto-optical characteristics of each of these magneto-optical recording media were measured from the substrate side.
It is shown in FIG. FIG. 13 (A) corresponds to a case where a 200 ° ZrN base film is provided, and FIG. 13 (B) corresponds to a case where a ZrN base film is not provided. Comparing these figures, when the ZrN underlayer was not provided, the coercive force was 225 Oe and the magnetic Kerr rotation angle was 0.
In contrast to 17 °, when the ZrN underlayer was provided, the coercive force and the magnetic Kerr rotation angle were improved, and the squareness was significantly improved.

FIG. 14 shows a change in coercive force depending on the thickness of the ZrN underlayer. As shown in this figure, the coercive force reaches saturation near the layer thickness of 500 °, and the value at that time is about twice as large as the case where the ZrN underlayer is not provided.

Further, FIG. 15 shows a change in the magnetic Kerr rotation angle depending on the layer pressure of the ZrN underlayer. According to this figure, the magnetic Kerr rotation angle periodically changes with respect to the layer thickness of the ZrN underlayer, and at the peak, the enhancement effect is twice or more as compared with the case where the ZrN underlayer is not provided. I have. However, in a certain layer thickness region, a so-called reversal phenomenon of the magnetic Kerr curve in which the magnetic Kerr rotation angle becomes a negative value after passing through 0 appears, so that it is necessary to consider an optimum layer thickness in practical use.

A similar reversal phenomenon of the magnetic Kerr curve appeared more remarkably when the TiN underlayer was used under the same conditions as shown in FIG.

Fifth Embodiment The fourth embodiment described above is an example in which a ZrN underlayer and a magneto-optical recording medium are used. However, in the present embodiment, a Cor layer is formed on a glass substrate through another underlayer made of a nitride dielectric. 5 is an example of a magneto-optical recording medium on which a Pd-based artificial lattice film is formed.

The nitride dielectric used in this example is Si ₃ N ₄ , AlN and
BN. A magneto-optical recording medium using these was prepared as follows. First, according to the method of the above-described fourth embodiment, Si ₃ N ₄ underlayers, AlN underlayers, or BN underlayers of various thicknesses were formed on a glass substrate. Subsequently, in an argon atmosphere at a gas pressure of 11 mTorr, DC sputtering of input power of 0.35 A, 300 V was performed for Co, and high-frequency sputtering of input power of 360 W was performed for the Pd target. The layers were sequentially laminated to form a Co-Pd-based artificial lattice film having a total thickness of 100 °, and a magneto-optical recording medium was produced. For comparison, a magneto-optical recording medium without a base film was similarly prepared.

The magnetic Kerr curves of the magneto-optical characteristics of each of these magneto-optical recording media measured from the substrate side are shown in FIGS.
It is shown in FIG. 17 (D). FIG. 17 (A) is a 1300 ° Si ₃ N ₄ underlayer, FIG. 17 (B) is a 300 ° AlN underlayer, and FIG. 17 (C) is
This is equivalent to the case where each of the 1200 mm
FIG. 3D shows the case where no base film is provided. here,
The coercive force when no underlayer is provided is 675 Oe, and the magnetic Kerr rotation angle is 0.195 °. In contrast, coercivity Any case of providing a base film, squareness, improved magnetic Kerr rotation angle, significant improvement was observed particularly when the Si ₃ N ₄ base film.

Here, FIG. 18 shows a change in the magnetic Kerr rotation angle depending on the layer thickness of the Si ₃ N ₄ underlayer, and FIG. 19 shows a change in the magnetic Kerr rotation angle depending on the layer thickness of the AlN underlayer. It is clear from these figures that the optimum layer thickness exists in each case, and the enhancement effect at the peak is more than twice as large as the case where the base film is not provided.

Sixth Embodiment In all of the above embodiments, examples have been described in which a nitride dielectric is used as a base film. Next, examples in which an oxide dielectric is used as a base film will be described.

In the present embodiment, a glass substrate was coated with a Ta ₂ O ₅
5 is an example of a magneto-optical recording medium on which a Pt-based artificial lattice film is formed.

This magneto-optical recording medium was prepared as follows. That is, first, gas pressure was measured using a Ta ₂ O ₅ target with a diameter of 100 mm.
RF sputtering was performed at a power of 300 W in an argon atmosphere of 4 mTorr, and 1600 mm of Ta ₂ O ₅ was deposited on a glass substrate.
An underlayer was deposited. Subsequently, in an argon atmosphere at a gas pressure of 4 mTorr, the input power was set to 0.4 at a rotation speed of the rotating base of 16 rpm.
A Co layer was formed by DC sputtering at 0 A and 300 V, and a Pt layer was sequentially formed on the glass substrate by high-frequency sputtering at a power of 350 W to form a Co-Pt-based artificial lattice film having a total thickness of 100 mm. Created media. For comparison, a magneto-optical recording medium without a Ta ₂ O ₅ underlayer was similarly prepared.

FIG. 20 (A) and FIG. 20 (A) show the magnetic Kerr curve when the magneto-optical characteristics of each of these magneto-optical recording media were measured from the substrate side.
The results are shown in FIG. FIG. 20 (A) corresponds to a case where a Ta ₂ O ₅ base film of 1600 ° is provided, and FIG. 20 (B) corresponds to a case where a Ta ₂ O ₅ base film is not provided. First, when the Ta ₂ O ₅ underlayer was not provided, the magnetic Kerr rotation angle was 0.84 ° and the coercive force was 180 Oe. On the other hand, when the Ta ₂ O ₅ underlayer was provided, the magnetic Kerr rotation angle was 0.98 ° and the coercive force was 225 Oe, both of which increased.

Then, next, it was examined how the magnetic Kerr rotation angle and the coercive force change depending on the thickness of the Ta ₂ O ₅ underlayer. That is, high-frequency sputtering was performed at an input power of 300 W in an argon atmosphere at a gas pressure of 4 mTorr, and Ta ₂ O ₅ underlayers of various thicknesses were deposited on a glass substrate. Then gas pressure 4mTor
In an argon atmosphere of r, the rotation speed of the rotating base was set to 16 rpm, and a Co layer was formed by DC sputtering (input power: 0.40 A, 300 V), and high-frequency sputtering (input power: 4
50 W), a Pt layer is sequentially laminated on the glass substrate,
A 100-mm thick Co-Pt-based artificial lattice film was formed, and a magneto-optical recording medium was prepared. FIG. 21 shows the results of measuring the magneto-optical characteristics of these magneto-optical recording media. In the figure, the vertical axis represents the magnetic Kerr rotation angle θ _K (゜) or the coercive force (Oe) measured from the substrate side, and the horizontal axis represents the layer thickness (Å) of the Ta ₂ O ₅ underlayer. ) Indicates the magnetic Kerr rotation angle θ _K , and the white square (□) indicates the coercive force. Also, a black circle (●) are values theta _K at measuring the magnetic Kerr rotation angle of the magneto-optical recording medium without the Ta ₂ O ₅ base film from the film side. First, it should be noted that even when the Ta ₂ O ₅ underlayer is not provided, the magnetic Kerr rotation θ _K measured from the substrate side is larger than the magnetic Kerr rotation angle θ _K measured from the recording layer side. This is a manifestation of an enhancement effect reflecting the refractive index of the substrate. The magnetic Kerr rotation angle θ _K measured from the substrate side is
The maximum value is obtained when the thickness of the Ta ₂ O ₅ underlayer is around 800 mm. On the other hand, the coercive force increases up to a thickness of about 600 mm of the Ta ₂ O ₅ base film as compared with the case where no base film is provided, but decreases with a larger layer thickness.

Next, in this embodiment, an attempt is made to evaluate the square of the magnetic Kerr curve, which has been evaluated with squareness, by using a value ΔH which is considered to be a measure of anisotropic energy. This Δ
H is the strength of the magnetic field when the magnetic car rotation angle reaches saturation
Represented by the difference between the strength of H ₂ magnetic field when the H ₁ and saturated magnetic Kerr rotation angle starts to increase _{(ΔH = H 1 -H 2)} , smaller the value increases perpendicular magnetic anisotropy energy, Alternatively, it is considered that the uniformity of the anisotropic energy is improved. No.
ΔH in FIG. 20 (A) is 350 Oe, and ΔH in FIG. 20 (B) is 540 Oe. According to this evaluation method, the case where the Ta ₂ O ₅ base film is provided has better magneto-optical characteristics. Is confirmed.

Seventh Embodiment This embodiment is an example of a magneto-optical recording medium having a Ta ₂ O ₅ upper dielectric layer on the Co—Pt-based artificial lattice film of the magneto-optical recording medium prepared in the sixth embodiment. It is.

The Ta ₂ O ₅ upper dielectric layer was formed in the same manner as the Ta ₂ O ₅ underlayer, and finally a Pt reflection film was formed.

First, a Ta ₂ O ₅ underlayer and a Ta ₂ O ₅
FIG. 22 shows the result of examining the change in coercive force depending on the thickness of the upper dielectric layer. In the figure, the vertical axis is the coercive force (Oe), and the horizontal axis is
Ta ₂ O ₅ represents the thickness (Å) of the upper dielectric layer. Each curve corresponds to the case where Ta ₂ O ₅ underlayers with various layer thicknesses are provided. The open circles (○) are plots of squares (□) when no Ta ₂ O ₅ underlayers are provided. Is Ta ₂ O ₅ underlayer 180Å
In the case of, the plot of diamonds (◇) represents the case of 230Å, the plot of white triangles (△) represents the case of 350Å, and the plot of black triangles (▲) represents the case of 700Å. Also in the FIG. 23 shows the result of examining the change in the magneto-optical recording medium of the Ta ₂ O ₅ base film and Ta ₂ O ₅ magnetic Kerr rotation angle of the substrate side due to the thickness of the upper dielectric layer theta _K. In the figure, the vertical axis is the magnetic Kerr rotation angle θ _K (゜), and the horizontal axis is the thickness of the Ta ₂ O ₅ upper dielectric layer (Å).
Represents The meaning of each curve is the same as in the case of FIG. 22 described above.

22 and 23 that the coercive force is Ta ₂ O ₅
It can be seen that the state changes variously depending on the combination of the thicknesses of the base film and the upper dielectric layer of Ta ₂ O ₅ . Ta ₂ O ₅
When only the upper dielectric layer of a ₂ O ₅ is provided, the coercive force tends to decrease as a whole. On the other hand, when the Ta ₂ O ₅ underlayer is provided with a certain layer thickness, the coercive force increases when the thickness of the Ta ₂ O ₅ upper dielectric layer exceeds the thickness of the Ta ₂ O ₅ underlayer. In particular, the thickness of the Ta ₂ O ₅ underlayer was 180Å
In the case of (3), it increases remarkably to 410 Oe, in the case of 230 °, to 570 Oe, and in the case of 350 °, to 700 Oe. Further, the magnetic Kerr rotation angle θ _K also changes depending on the thickness of the Ta ₂ O ₅ underlayer, and the enhancement effect appears up to a certain layer thickness of the Ta ₂ O ₅ upper dielectric layer. Therefore, it is possible to improve both the coercive force and the magnetic Kerr rotation angle by appropriately selecting the thicknesses of the Ta ₂ O ₅ base film and the Ta ₂ O ₅ upper dielectric layer.

Eighth Embodiment This embodiment is an example of a magneto-optical recording medium using a polycarbonate substrate instead of the glass substrate in the sixth embodiment.

This magneto-optical recording medium was prepared as follows. That is, a Ta ₂ O ₅ underlayer was formed in various thicknesses in the same manner as in the sixth embodiment except that a polycarbonate substrate was used as the substrate. Subsequently, in an argon atmosphere with a gas pressure of 4 mTorr, the rotation speed of the rotating base was increased to 16 rp.
DC sputtering as m (input power: 0.40A, 300V)
And a Pt layer was sequentially laminated on the glass substrate by high-frequency sputtering (input power: 450 W) to form a Co-Pt-based artificial lattice film having a total thickness of 100 mm, thereby producing a magneto-optical recording medium. . For comparison, a magneto-optical recording medium without a Ta ₂ O ₅ underlayer was similarly prepared.

The magnetic Kerr curves of the magneto-optical characteristics of each of these magneto-optical recording media measured from the substrate side are shown in FIGS.
This is shown in FIG. FIG. 24 (A) shows a case where a 30 ° Ta ₂ O ₅ base film is provided, FIG. 24 (B) shows a case where a 130 ° Ta ₂ O ₅ base film is provided, and FIG. 24 (C) shows a case where a 220 ° Ta film is provided. FIG. 24 (D) corresponds to the case where the base film is not provided when the ₂ O ₅ base film is provided. First, the coercive force without a Ta ₂ O ₅ underlayer was 1
80 Oe. On the other hand, the coercive force of the obtained magneto-optical recording medium increases as the layer thickness increases, with 230 Oe when the Ta ₂ O ₅ underlayer of 30 ° is provided, 250 Oe at 130 °, and 270 Oe at 220 °. This is probably because the provision of the underlayer increases the perpendicular magnetic anisotropy energy.

Ninth Embodiment This embodiment is an example of a magneto-optical recording medium using a Co-Pt-based artificial lattice film in place of the Co-Pt-based artificial lattice film in the sixth embodiment.

This magneto-optical recording medium was prepared as follows. That is, a 1000 ° Ta ₂ O ₅ underlayer was first deposited on a glass substrate in the same manner as in the above-described sixth embodiment. Subsequently, in an argon atmosphere with a gas pressure of 12 mTorr, the rotation speed of the rotating base was set to 16 rpm, and a Co layer was formed by DC sputtering (input power: 0.35 A, 300 V), and a Pd layer was formed by high frequency sputtering (input power: 330 W). A Co-Pd-based artificial lattice film having a total thickness of 100 ° was formed on the above glass substrate in order to form a magneto-optical recording medium. For comparison, a magneto-optical recording medium without a Ta ₂ O ₅ underlayer was similarly prepared.

FIG. 25 (A) and FIG. 25 (A) show the magnetic Kerr curve when the magneto-optical characteristics of each of these magneto-optical recording media were measured from the substrate side.
This is shown in FIG. FIG. 25 (A) corresponds to a case where a Ta ₂ O ₅ base film is provided, and FIG. 25 (B) corresponds to a case where a Ta ₂ O ₅ base film is not provided. First, when no Ta ₂ O ₅ underlayer was provided, the magnetic Kerr rotation angle was 0.21 °, the coercive force was 640 Oe, and ΔH was about 380.
Oe. In contrast, when a Ta ₂ O ₅ underlayer is provided, the magnetic Kerr rotation angle is 0.21 °, the coercive force is 570 Oe, and ΔH is about 75 Oe.
It can be seen that, although the coercive force is slightly reduced as compared with the case where the underlayer is not provided, ΔH is about １, and excellent perpendicular magnetic anisotropy is exhibited.

Tenth Embodiment Although the sixth to ninth embodiments described above are examples of a magneto-optical recording medium using a Ta ₂ O ₅ underlayer, this embodiment is different from the first embodiment in that another oxide is formed on a glass substrate. Via a dielectric film
This is an example of a magneto-optical recording medium on which a Co-Pd-based artificial lattice film is formed.

The oxide dielectric used in this example was SiO ₂ and Al ₂ O ₃
It is.

A magneto-optical recording medium using these was prepared as follows. That is, a gas pressure of 4 m in an argon gas atmosphere
Sputtering was performed at Torr, and a SiO ₂ base film and an Al ₂ O ₃ base film with various thicknesses were deposited on a glass substrate. Subsequently, in an argon atmosphere at a gas pressure of 12 mTorr, a Co layer was sequentially laminated on each of these glass substrates by DC sputtering (input power: 0.35 A, 300 V), and a Pd layer was deposited by high frequency sputtering (input power: 330 W). As a result, a Co-Pd-based artificial lattice film having a total thickness of 100 mm was formed, and a magneto-optical recording medium was produced. For comparison, a magneto-optical recording medium without a base film was similarly prepared.

The magnetic Kerr curves of the magneto-optical characteristics of each of the magneto-optical recording media measured from the substrate side are shown in FIGS.
It is shown in FIG. FIG. 26 (A) shows a 500 ° SiO ₂ underlayer,
FIG. 26 (B) shows a 20 ° Al ₂ O ₃ base film, and FIG.
26 corresponds to the case where the Al ₂ O ₃
FIG. 3D shows the case where no base film is provided.

First, the rotation angle of the magnetic car when the underlayer is not provided is 0.
32 ゜, the coercive force is 1100 Oe. In contrast, 500Å of SiO
_{(2) When the} underlayer is provided, the magnetic Kerr rotation angle is 0.38 ° and the coercive force is 1000 Oe. The coercive force is slightly reduced, but the magnetic Kerr rotation angle and the squareness are improved. Such improvement of the magnetic Kerr rotation angle and squareness is observed even when the Al ₂ O ₃ underlayer is provided.

Eleventh Embodiment This embodiment uses a polycarbonate substrate instead of the glass substrate in the above-described embodiment of FIG. 10, and forms a Co-Pd-based artificial lattice film through an Al ₂ O ₃ underlayer. It is an example of a magnetic recording medium.

This magneto-optical recording medium was prepared as follows. That is, sputtering was performed at a gas pressure of 4 mTorr in an argon gas atmosphere, and Al ₂ O ₃ underlayers of various thicknesses were deposited on a polycarbonate substrate. Subsequently, the tenth
In the same manner as in the procedure of the embodiment shown in FIG.
A d-system artificial lattice film was formed, and a magneto-optical recording medium was created.

The magnetic Kerr curves of the magneto-optical characteristics of each of these magneto-optical recording media measured from the substrate side are shown in FIGS.
This is shown in FIG. 27 (D). FIG. 27 (A) shows a case where an Al ₂ O ₃ underlayer of 20 ° is provided, FIG. 27 (B) shows a case where an Al ₂ O ₃ underlayer of 100 ° is provided, and FIG. case of providing ₂ O ₃ base film, view the 27 (D) corresponds to the case where not provided Al ₂ O ₃ base film. From these figures, it can be seen that the Al ₂ O ₃
It can be seen that the coercive force increases even with a layer thickness as small as about 0 °, and that the squareness improves as the layer thickness increases.

In the above embodiments, the magneto-optical recording medium having a Co-Pt-based artificial lattice film or a Co-Pd-based artificial lattice film as a recording layer has been described, but the present invention is limited to the above-described embodiments. Not Co, Pd layer and Pt
The same dielectric substance is also used for a magnetic recording medium having a Co-Pd-Pt-based artificial lattice film in which a Co layer and a Pd-Pt alloy layer are laminated in an appropriate layer thickness and in an appropriate order. The effect of the underlayer can be expected.

〔The invention's effect〕

As is clear from the above description, in the magneto-optical recording medium according to the present invention, Co-Pd-based, Co-Pt-based or
By providing a dielectric underlayer between the recording layer made of the o-Pd-Pt-based artificial lattice film and the substrate, the perpendicular magnetic anisotropy energy of the recording layer is increased. Thereby, the shape of the write bit is sharpened, and the C / N ratio at the time of reading is improved. Further, when the thickness of the underlayer is optimally selected, an increase in the magnetic Kerr rotation angle can be expected. Therefore, high-quality and high-density magneto-optical recording can be performed.

Furthermore, since the above-mentioned artificial lattice film does not use rare earth elements that are expected to be tightly supplied worldwide,
A stable and economical supply of magneto-optical recording media can be expected.

If such a magneto-optical recording medium is used as a storage medium for a magneto-optical memory such as a so-called beam-addressable file memory for performing writing using a light beam and performing reading using the magnetic Kerr effect, it is extremely high. A memory device having a high density and a high C / N ratio and maintaining high reliability for a long time can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing the most basic configuration of a magneto-optical recording medium according to the present invention. 2 to 4 are schematic sectional views showing other examples of the configuration of the magneto-optical recording medium according to the present invention. FIG. 2 shows an example in which a metal reflective film is provided on a recording layer, and FIG. FIG. 4 shows an example in which a dielectric layer is provided on a recording layer, and FIG. 4 shows an example in which a dielectric layer and a metal reflection film are provided in this order on the recording layer. FIGS. 5 (A) to 5 (C) show magneto-optics of a magneto-optical recording medium in which a Co-Pt-based artificial lattice film is formed on a glass substrate via a Si ₃ N ₄ underlayer of various thicknesses. FIG. 5 (A) is a magnetic Kerr curve showing characteristics.
FIG. 5B shows a case where the thickness of the Si ₃ N ₄ underlayer is 550 °.
In the case of 50 °, FIG. 5C shows a comparative example in which no Si ₃ N ₄ base film was provided. FIG. 6 is a characteristic diagram showing changes in coercive force and magnetic Kerr rotation angle depending on the thickness of the Si ₃ N ₄ underlayer in the same magneto-optical recording medium. 7 (A) and 7 (B) show the results on a polycarbonate substrate.
FIG. 7 (A) is a magnetic Kerr curve showing a change in magneto-optical characteristics depending on the presence or absence of a Si ₃ N ₄ underlayer in a magneto-optical recording medium on which a Co—Pt-based artificial lattice film is formed. ₃ N ₄
If having a base film, Si ₃ N Figure 7 (B) is a comparative example
₄ represents a case without a base film. FIG. 8 is a characteristic diagram showing changes in coercive force and squareness depending on the thickness of the Si ₃ N ₄ underlayer in the same magneto-optical recording medium. FIG. 9 is a characteristic diagram showing a change in the magnetic Kerr rotation angle depending on the thickness of the Si ₃ N ₄ underlayer in the same magneto-optical recording medium. Fig. 10 (A)
FIG. 10 (D) is a magnetic Kerr curve showing the magneto-optical characteristics of a magneto-optical recording medium in which a Co-Pt-based artificial lattice film is formed on a glass substrate via an underlayer made of another nitride dielectric. FIG. 10 (A) shows a case where a ZrN underlayer with a layer thickness of 480 mm is provided, FIG. 10 (B) shows a case where a BN underlayer with a layer thickness of 400 mm is provided, and FIG. FIG. 10 (D) shows the case where the underlayer was not provided as a comparative example. FIG. 11 is a characteristic diagram showing changes in coercive force and magnetic Kerr rotation angle depending on the thickness of the ZrN underlayer in the magneto-optical recording medium having a ZrN underlayer. Twelfth
The figure is a characteristic diagram showing a change in coercive force depending on the thickness of the TiN underlayer in the magneto-optical recording medium having a TiN underlayer instead of the ZrN underlayer. Fig. 13 (A) and Fig. 13 (B)
FIG. 13A is a magnetic Kerr curve showing a change in magneto-optical characteristics depending on the presence or absence of a ZrN underlayer in a magneto-optical recording medium in which a Co—Pd-based artificial lattice film is formed on a glass substrate. FIG. FIG. 13 (B) shows a case without a ZrN base film as a comparative example. First
FIG. 4 is a characteristic diagram showing a change in coercive force depending on the thickness of the ZrN underlayer in the same magneto-optical recording medium. FIG. 15 is a characteristic diagram showing a change in the magnetic Kerr rotation angle depending on the thickness of the ZrN underlayer in the same magneto-optical recording medium. FIG. 16 is a characteristic diagram showing a change in the magnetic Kerr rotation angle depending on the thickness of the TiN underlayer in the magneto-optical recording medium having a TiN underlayer instead of the ZrN underlayer. FIGS. 17 (A) to 17 (D) show Co on a glass substrate through another underlayer made of a nitride dielectric.
FIG. 17 (A) is a magnetic Kerr curve showing magneto-optical characteristics of a magneto-optical recording medium on which a Pd-based artificial lattice film is formed.
If provided Si ₃ N ₄ base film of 1300 Å, when view the 17 (B) is provided with an AlN underlayer having a thickness of 300 Å, view the 17 (C) is a layer thickness
FIG. 17 (D) shows a case where a BN underlayer of 1200 ° is provided and a case where no underlayer is provided as a comparative example. 18th
The figure is a characteristic diagram showing a change in the magnetic Kerr rotation angle depending on the thickness of the Si ₃ N ₄ underlayer in the same magneto-optical recording medium. FIG. 19 is a characteristic diagram showing a change in the magnetic Kerr rotation angle depending on the thickness of the AlN underlayer in the same magneto-optical recording medium. FIGS. 20 (A) and 20 (B) show changes in magneto-optical characteristics of a magneto-optical recording medium having a Co—Pt-based artificial lattice film formed on a glass substrate depending on the presence or absence of a Ta ₂ O ₅ underlayer. FIG. 20 (A) shows a magnetic Kerr curve. FIG. 20 (A) shows a case having a Ta ₂ O ₅ underlayer with a thickness of 200 °, and FIG. 20 (B) shows a comparative example without a Ta ₂ O ₅ underlayer. . Fig. 21 shows a glass substrate
FIG. 3 is a characteristic diagram showing a change in magneto-optical characteristics depending on the thickness of a Ta ₂ O ₅ underlayer in a magneto-optical recording medium on which a Co—Pt-based artificial lattice film is formed. FIG. 22 shows a change in coercive force due to a combination of the thicknesses of the Ta ₂ O ₅ underlayer and the Ta ₂ O ₅ upper dielectric layer in the magneto-optical recording medium having a Co-Pt-based artificial lattice film formed on a glass substrate. FIG. 23 is a characteristic diagram showing a change in the magnetic Kerr rotation angle in the same magneto-optical recording medium. FIGS. 24 (A) to 24 (D) show magneto-optics of a magneto-optical recording medium in which a Co-Pt-based artificial lattice film is formed on a polycarbonate substrate via a Ta ₂ O ₅ underlayer of various thicknesses. FIG. 24 (A) is a magnetic Kerr curve showing characteristics. FIG. 24 (A) shows a case where the thickness of the Ta ₂ O ₅ underlayer is 30 °, and FIG.
FIG. 24 (C) shows the case where the angle is 220 °, and FIG. 24 (D) shows the case where no Ta ₂ O ₅ base film is provided as a comparative example.
FIGS. 25 (A) and 25 (B) show Co on a glass substrate.
-In magneto-optical recording media with Pd-based artificial lattice film formed
Ta ₂ O with and without ₅ underlayer is a magnetic Kerr curve showing the change in the magneto-optical properties, Ta ₂ O ₅ of Figure 25 (A) is the layer thickness 1000Å
FIG. 25 (B) shows an example in which Ta ₂ O
₅ represents a case without a base film. Fig. 26 (A)
FIG. 26 (D) is a magnetic Kerr curve showing the magneto-optical characteristics of a magneto-optical recording medium in which a Co—Pd-based artificial lattice film is formed on a glass substrate via a base film made of another oxide dielectric. FIG. 26 (A) shows the case where an SiO ₂ underlayer with a layer thickness of 500 ° is provided, FIG. 26 (B) shows the case where an Al ₂ O ₃ underlayer with a thickness of 20 ° is provided, and FIG. 26 (C) shows the layer FIG. 26D shows a case where an Al ₂ O ₃ base film having a thickness of 60 ° is provided and a case where no base film is provided as a comparative example. Fig. 27 (A) to Fig. 27 (D)
FIG. 27 is a characteristic diagram showing a magnetic Kerr curve of a magneto-optical recording medium in which a Co—Pd-based artificial lattice film is formed on a polycarbonate substrate via Al ₂ O ₃ underlayers of various thicknesses. ) Is
When the layer thickness of the Al ₂ O ₃ underlayer is 20 mm, FIG.
27 (C) shows the case where the angle is 150 °, and FIG. 27 (D) shows the case where no Al ₂ O ₃ base film is provided as a comparative example. DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Dielectric base film 3 ... Recording layer 4 ... Metal reflective film 5 ... Dielectric layer

Claims (1)

(57) [Claims] An artificial lattice film in which a Co layer and a Pt layer and / or a Pd layer are alternately laminated is used as a recording layer, and the recording layer is made of Al.
₂ O ₃ , Ta ₂ O ₅ , MgO, SiO ₂ , TiO ₂ , Fe ₂ O ₃ , ZrO ₂ , Bi ₂ O ₃ , Z
A magneto-optical recording medium formed on a substrate via a derivative base film made of any one of rN, TiN, Si ₃ N ₄ , AlN, AlSiN, BN, TaN, and NbN.