JPH0528553A - Magneto-optical recording medium and production thereof - Google Patents

Abstract

PURPOSE:To improve the coercive force and perpendicular magnetic anisotropy of the artificial lattice films of the magneto-optical recording medium formed with the artificial lattice films of an iron family-platinum group system as a recording layer. CONSTITUTION:The artificial lattice films constituted by using the laminate laminated with a 1st layer 2 consisting of the metals selected from Co, Fe and Co-Fe alloy and a 2nd layer 3 consisting of the metal selected from Pt, Pd and Pt-Pd alloy as a repetitive unit 4 are formed on a substrate 1 consisting of a suitable material, such as glass or plastic. The artificial lattice films are formed in a gaseous atmosphere contg. elements (for example, O, N, H, C, S, F) which can decrease the saturation magnetization of the 1st layer 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium for recording / reproducing information with a laser beam or the like by utilizing the magneto-optical effect, and can realize particularly good perpendicular magnetic anisotropy and high coercive force. The present invention relates to a magneto-optical recording medium and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, as a rewritable high-density recording method, a magneto-optical recording medium for recording / reproducing with a semiconductor laser beam has attracted attention.

Conventionally, as magnetic materials used in magneto-optical recording media, rare earth elements such as Gd, Tb and Dy and Fe,
Amorphous alloys in combination with transition metal elements such as Co have been used. However, the rare earth elements and Fe constituting these amorphous alloys are easily oxidized, and there is a drawback that corrosion is likely to occur in a hot and humid environment.

On the other hand, a Co-Pt system using a noble metal such as Pt or Pd instead of the rare earth element, or Co-P
The d-type recording material is excellent in corrosion resistance, and a technique in which this system is used as an artificial lattice film to increase the coercive force is disclosed in Japanese Patent Laid-Open No.
No. 98144, JP-A-1-162257, and the like. According to these, in an extremely thin film thickness range of about 200 Å, a coercive force of about 100 to 200 Oe is obtained for a Co-Pt-based artificial lattice film, and a coercive force of about 500 to 2000 Oe is obtained for a Co-Pd-based artificial lattice film. It becomes a magnetic film. Here, the artificial lattice film is a so-called superlattice film or a modulation structure film, and a plurality of layers having different constituents and having a thickness of several tens of atomic layers or less are regularly and repeatedly laminated with a predetermined thickness. That is what was done.

[0005]

However, in the magneto-optical recording medium using the above-mentioned conventional artificial lattice film, the magnitude of the coercive force and the perpendicular magnetic anisotropy of the recording layer stabilizes the magneto-optical recording. There is a problem that it is not enough to carry out.

An object of the present invention is to provide a magneto-optical recording medium which has a sufficiently large coercive force and perpendicular magnetic anisotropy of an artificial lattice film used as a recording layer and which can be manufactured under wider film forming conditions. , To provide a manufacturing method thereof.

[0007]

A method of manufacturing a magneto-optical recording medium according to the present invention comprises a first layer made of a metal selected from Co, Fe and Co-Fe alloys, and Pt, Pd and Pt-. In a method of manufacturing a magneto-optical recording medium having an artificial lattice film in which a second layer made of a metal selected from the alloys of Pd alloys is repeatedly laminated, the saturation magnetization of the first layer is reduced. It is characterized in that the artificial lattice film is formed in a gas atmosphere containing an element capable of being added.

The magneto-optical recording medium of the present invention comprises a first metal selected from Co, Fe and Co--Fe alloys.
And a second layer made of a metal selected from the alloys of Pt, Pd, and Pt-Pd alloy, which are repeatedly laminated to form an artificial lattice film as a recording layer.
At least one element produced by the method for producing a magneto-optical recording medium according to the present invention and capable of decreasing the saturation magnetization of the first layer is contained in the first layer in an atomic ratio of 1 to 30.
%include.

The magneto-optical recording medium of the present invention will be described in detail below.

FIG. 1 is a sectional view of an example of a magneto-optical recording medium according to the present invention. The magneto-optical recording medium shown in FIG. 1 includes a first layer 2 made of a metal selected from Co, Fe and Co-Fe alloys, and Pt, Pd and Pt-.
A repeating unit 4 is formed by stacking a second layer 3 made of a metal selected from Pd alloys, and an artificial lattice film having a structure in which the repeating unit 4 is regularly and repeatedly stacked is used as a recording layer. It is a thing. This recording layer is provided on the substrate 1 made of an appropriate material such as glass or plastic.

The layer thickness of the first layer 2 is preferably about 2 to 30Å, and the layer thickness of the second layer 3 is preferably about 3 to 40Å. In each repeating unit 4, the layer thickness of the first layer 2 is uniform, and the layer thickness of the second layer 3 is also uniform. It is desirable that the finally laminated artificial lattice film, that is, the recording layer has a thickness of about 50 to 800 Å.

Each of these layers contains elements such as O, N, H, C and S in an atomic number ratio of about 1% to 30%. The interface constituting the artificial lattice film described above, that is, the first layer and the second layer
It is desirable that the interface with the layer is flat, with atoms in both layers not disturbing each other, but it is a composition-modulated structure in which the composition fluctuates while maintaining a constant period even though the interface is slightly disturbed. It may be. This artificial lattice film can be formed by sputtering, vacuum deposition, molecular beam epitaxy (MBE), or the like. In addition, various elements may be added for the purpose of increasing thermal stability or changing the Curie temperature. For example, as the element added to the first layer, B, C, Al, Si, P, Ti, V, Ni, C
It is preferably at least one of u, Ga, Ge, Zr, Nb, Mo, In, Sn and Sb. For example, as the element to be added to the second layer, in addition to the same element as the first layer, C
r, Mn, Co, Zn, Y, Rh, Ag, La, Nd, Sm, E
Examples include u, Ho, Hf, W, Ir, Au, Pb and Bi.

When the above-mentioned artificial lattice film is used as a recording layer of a magneto-optical recording medium, this recording layer is generally formed on a transparent substrate. In this case, on both sides of this recording layer,
It is possible to provide a protective layer using a metal, a semimetal, a semiconductor, or a dielectric. When a metal material is used as the protective layer, Cu, Rh, Pd, Ag, which has a face-centered cubic structure,
Ir, Pt, Au and W having a body-centered cubic structure
It is preferable to provide the film with a film thickness of up to 500 Å. When a dielectric is used, Al ₂ O ₃ , Ta ₂ O ₅ , MgO, SiO ₂ , Fe ₂ O ₃ ,
Oxide compounds such as ZrO ₂ and Bi ₂ O ₃ , or Zr
N, TiN, Si ₃ N ₄ , AlN, AlSiN, BN, TaN,
It is preferable to provide a nitrogen compound such as NbN with a film thickness of 5 to 5000 Å. When a semi-metal or a semiconductor is used, Si, Ge, ZnSe, SiC, ZnS or the like may be provided in a film thickness of 5 to 5000Å.

In addition to the recording layer and the protective layer, it is possible to provide a layer having a high reflectance. For example,
If the recording layer is an ultrathin film of 200 Å or less, most of the incident light will pass through the recording layer. In general, light for recording and reading is incident from the side of a substrate made of a transparent material, and therefore, by providing a reflective layer on the side opposite to the recording layer when viewed from the side of the substrate, the magneto-optical of light transmitted through the recording layer is provided. The effect can be fully utilized. As this reflective layer,
Appropriate metals can be used.

[0015]

In a conventional magneto-optical recording medium using a Co-Pd or Co-Pt artificial lattice film as a recording layer, the saturation magnetization of the artificial lattice film, which is the recording layer, is large. The magnetic anisotropy of (i.e., perpendicular magnetic anisotropy) was not sufficient. Where Co, Fe and Co-Fe
When an artificial lattice film that is a recording layer is formed under the condition that an element capable of reducing the saturation magnetization of a layer made of a metal selected from the alloy is mixed in this layer, As a result, the saturation magnetization decreases and the coercive force and perpendicular magnetic anisotropy close to those of the rare earth-transition metal amorphous alloy system are exhibited.

[0016]

EXAMPLES Next, examples of the present invention will be described with reference to comparative examples and numerical values. [Example 1] Co and Pd targets each having a diameter of 3 inches were placed in a magnetron sputtering apparatus. As described in detail below, a slide glass substrate is placed at a position facing these targets, sputtering is performed under conditions such that the gas pressure during sputtering is 5 mTorr, and an artificial lattice film is formed on the slide glass substrate. The following recording layers were formed to prepare samples of magneto-optical recording media (Examples 1-1 to 6).

For sputtering, a mixture of Ar and a gas as shown in Table 1 was used, and the flow rate of the entire gas was set to 20 SCCM (equivalent to 20 cc at standard condition [0 ° C., 1 atmosphere]). I did it. For example, in Example 1-1, 10 SCCM of pure Ar gas and 10 SCCM of gas in which Ar is mixed with 5% of O ₂ are introduced into the apparatus while being mixed. At this time, the O ₂ concentration (volume ratio) is 2.5%.

The target of Co is 0.1A-300V
DC of 0.15A- is applied to the Pd target.
Simultaneous DC sputtering is performed under the condition that a DC of 300 V is applied, and by alternately opening and closing the shutter plates provided on each of these targets, Co and Pd are alternately laminated on the slide glass substrate. Formed artificial lattice film. Table 1 shows the film thicknesses of the Co layer (first layer) and the Pd layer (second layer), and the total film thickness of the artificial lattice film as a whole.

Next, a sample vibration type magnetization measuring instrument (VSM),
Saturation magnetization (emu) of each of the obtained samples was measured by a Kerr effect measuring instrument using a laser beam with a wavelength of 830 nm.
/ Cc), coercive force (kOe), magnetic field (kOe) necessary for saturation of magnetization in the direction perpendicular to the film surface, and Kerr rotation angle (°) from the artificial lattice film surface were measured. Subsequently, the concentrations of light elements such as O, N, S, C, H and F in each sample were quantified by fluorescent X-ray analysis. The results are shown in Table 1. In addition, the volume ratio of the mixed gas shown in Table 1 shows the volume ratio of the additive gas (the gas other than Ar) in the introduced gas. [Comparative Example 1] Samples of magneto-optical recording media were prepared in the same manner as in Example 1 except that the additive gas was not added to the Ar gas used in sputtering, and Comparative Examples 1-1 and 2 were obtained.
Various magnetic properties were similarly measured for Comparative Examples 1-1 and 2. The results are shown in Table 1.

The above Examples 1-1 to 6 and Comparative Example 1-1,
From the results of No. 2, in Comparative Example 1-1, that is, the reference sample of the artificial lattice film of the Co—Pd system containing no additive, the saturation magnetization (both in the perpendicular direction and the in-plane direction) was large, and the magnetization saturation in the perpendicular direction was observed. Requires an applied magnetic field of 2.8 kOe. Here, a sample with an increased Pd ratio (Comparative Example 1-
In 2), it was possible to reduce the saturation magnetization to some extent, but the coercive force decreased to 0.6 kOe, and the applied magnetic field for saturation of the magnetization in the perpendicular direction increased to 3.0 kOe. This indicates that the saturation magnetization is reduced but the perpendicular magnetic anisotropy is not improved only by increasing the ratio of Pd and diluting the magnetism of Co.

On the other hand, the samples of Examples 1-1 to 6 are
In both cases, although the composition ratio between Co and Pd is the same as in Comparative Example 1-1, the saturation magnetization (especially in-plane direction)
, The applied magnetic field for saturation of magnetization in the perpendicular direction was greatly reduced, and the magnetic anisotropy in the perpendicular direction was improved.

The difference between Examples 1-1 to 6 and Comparative Example 1-2 is that in each of these Examples, light elements such as O, N, and S added at the time of sputtering are mixed in the Co or Fe lattice and the magnetic properties are reduced. It is thought that this is because not only is the strength weakened, but also a columnar shape having such a composition region on the outer periphery is formed to cause some form anisotropy.

[0023]

[Table 1] [Example 2 and Comparative Example 2] Table 2 shows the materials and film thicknesses to be placed on each of the two targets, the kind of gas to be added, the flow rate, etc., by the same sputtering as in Example 1 and Comparative Example 1. Samples (Examples 2-1 to 4 and Comparative examples 2-1 to 3) were prepared while changing the above. Also,
The evaluation of the prepared sample was also performed in the same manner as in Example 1 and Comparative Example 1 described above. The results are shown in Table 2.

Each of the samples of Example 2 and Comparative Example 2 contained the Fe element, and tended to be an in-plane anisotropic film as compared with the system containing only the Co element. Example 2-
From the results of Nos. 1 and 2 and Comparative Example 2-1, it was found that even in the Fe-Pd system, the addition of the elements O and N reduces the saturation magnetization and the vertical saturation magnetic field. In both Example 2-3 and Comparative example 2-2, FeCo alloy-P
Although it was a t-based system, Example 2-3 in which the N element was added had a decreased saturation magnetization, increased anisotropy in the vertical direction, and the Kerr rotation angle value was also measurable. Although both Example 2-4 and Comparative Example 2-3 are FeCo alloy-PtPd alloy system, in Example 2-4 in which O element is added,
The saturation magnetization decreased, and the magnitude of the residual magnetization in the perpendicular direction became a perpendicular magnetization film which was almost close to the saturation magnetization.

[0025]

[Table 2] From these results, it was found that Co-Fe-Pt-Pd-based thin films, which were conventionally difficult to be made into a perpendicular magnetization film, were repeatedly laminated to form an artificial lattice film, and C
By mixing a light element having the effect of diluting the magnetization of o and Fe into the sputtering, the magnetization can be reduced to a magnitude close to that of a rare earth element-transition metal element amorphous alloy conventionally used. It can be seen that this can improve the perpendicular magnetic anisotropy.

In the conventional rare earth element-transition metal element amorphous alloy, the rare earth element is easily oxidized, and if a light element is mixed during film formation, it often becomes an in-plane anisotropic film. It has been found that the Co-Fe-Pt-Pd system is superior in oxidation resistance, or rather, the anisotropy in the vertical direction is improved. Particularly, when the ratio of the mixed gas was about 1 to 10% by volume, particularly good results were shown. The ratio of these light elements taken into the artificial lattice film may change depending on the pressure during sputtering or the evacuation capacity, but it is effective to reduce the saturation magnetization to improve the perpendicular magnetic anisotropy. It is about 1 to 30 atomic%, and if it is less than this, the effect of addition is not obtained, and if it is more than this, the Curie temperature is lower than room temperature and the ferromagnetism is often not exhibited. In this case, O, N, S, C, H,
Since elements such as F have a high affinity for Co and Fe, even when the artificial lattice film is formed by the co-sputtering method, they are mixed in the layer made of Co and Fe,
It is considered that the layer made of Pt or Pd is hardly mixed.

With respect to the samples of the respective examples of the present invention, 0.1
a test of soaking in mol / l saline for 3 hours and 70
As a result of a test in which the test was left for 1 week in an environment of 90 ° C. and 90% relative humidity, there was almost no change in coercive force, saturation magnetization, Kerr rotation angle, etc. even after these tests, and the magneto-optical recording according to the present invention. It was found that good corrosion resistance and storage stability can be expected in the medium. Note that these tests were performed on a substrate in which the artificial lattice film was left exposed without providing a protective layer or the like.

[0028]

As described above, according to the present invention, Co,
A first layer made of a metal selected from Fe and Co-Fe alloys and a second layer made of a metal selected from alloys of Pt, Pd and Pt-Pd alloys were repeatedly laminated. In a magneto-optical recording medium having an artificial lattice film as a recording layer, the artificial lattice film layer is formed in a gas atmosphere containing an element capable of reducing the saturation magnetization of the first layer. As a result, the coercive force and the perpendicular magnetic anisotropy are improved, and the magneto-optical recording medium having stable characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of an example of a magneto-optical medium according to the present invention.

[Explanation of symbols]

1 substrate 2 First layer 3 Second layer 4 repeating units

Claims (3)

[Claims] 1. A first layer made of a metal selected from Co, Fe and Co-Fe alloys, and a second layer made of a metal selected from Pt, Pd and Pt-Pd alloy alloys. In a method of manufacturing a magneto-optical recording medium having an artificial lattice film in which layers are repeatedly laminated as a recording layer, the artificial lattice is formed under a gas atmosphere containing an element capable of reducing the saturation magnetization of the first layer. A method for manufacturing a magneto-optical recording medium, which comprises forming a film. 2. The element capable of reducing the saturation magnetization of the first layer is one or more kinds of elements selected from O, N, H, C, S and F. A method for manufacturing the magneto-optical recording medium described. 3. A first layer made of a metal selected from Co, Fe and Co-Fe alloys, and a second layer made of a metal selected from Pt, Pd and Pt-Pd alloy alloys. A magneto-optical recording medium having an artificial lattice film in which layers are repeatedly laminated as a recording layer, which is manufactured by the method for manufacturing a magneto-optical recording medium according to claim 1 or 2, and has a saturation magnetization of the first layer. A magneto-optical recording medium in which the first layer contains at least one element capable of reducing the amount of 1 to 30% in atomic ratio.