JPH02267722A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To obtain a recording medium which can be used for high density recording by forming a first base layer on a substrate, and successively a second and third base layers thereon and further forming a magnetic film comprising a Co-alloy and a carbon protective film thereon. CONSTITUTION:The first base layer 2 of a Cr film, the second base layer 3 of a C film, the third base layer 4 of a Cr film, the magnetic film 5 of a Co- alloy film and the carbon protective film 6 are successively formed on a glass substrate 1 at room temp. to produce the magnetic recording medium. By this method, the base Cr film 4 of the magnetic film 5 gives a highly oriented state of crystals and roughness, so that the magnetic film 5 has excellent epitaxial assist effect and magnetic peening effect. Thus, the obtd. medium has excellent magnetic characteristics such as coercive force and squareness ratio, namely, it can be used for high density recording.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a magnetic recording medium and a method for manufacturing the same, and more particularly to a magnetic recording medium such as a spanned hard disk used as an external recording medium for a computer, and a method for manufacturing the same. Regarding its manufacturing method.

(Prior Art) The hard disk is a typical example of the magnetic recording medium. Such conventional magnetic recording media were iron oxide coated type or Go plating type, but in recent years magnetic recording media capable of higher density recording have been developed to replace these and have begun to be put into practical use. There is.

Regarding the above-mentioned high-density magnetic recording medium, its structure is usually
As shown in the figure, three layers are formed on a substrate (1). The substrate (1) is an AI alloy or glass substrate with N1-P coating.

The three layers on the substrate (1) are a base layer (4) consisting of a C film (
It consists of a magnetic film (5) made of a Co alloy film (hereinafter referred to as a base Cr film), and a protective film (6) made of C, and the film thickness is usually 1000 to 3000, 500 to 700, and 500 to 700, respectively.
There are 300 to 400 people.

A sputtering method is adopted as the manufacturing method, and the substrate (1
), each of the above films is sequentially formed on top of the film.

This film formation requires one in-line sputtering device for mass production.
be used.

Magnetic properties include coercive force = 600-7000e, squareness ratio S
: 0.75 to 0.85 was obtained.

(A! Problem to be solved by the invention) Recently, there has been a strong demand for a magnetic recording medium that can record at higher density. For example, it has a coercive force of 1,000 to 15,000 e, and is suitable for playback as the trunk becomes narrower. In order to compensate for the decrease in output, there is a strong desire to develop a magnetic recording medium having a squareness ratio S of 0.9 or more.

However, conventional magnetic recording media have the problem that, due to their structure, there is a limit to the improvement of magnetic properties, and the above requirements cannot be met.

In other words, many factors are involved in the coercive force of a magnetic recording medium, but among them, the influence of the underlying Cr film is the largest.
The major factors are the evixaxial assist effect, which improves the crystal orientation of the magnetic film by the underlying Cr film, and the pinning effect, which traps domain walls in the magnetic film due to the roughness of the back surface of the underlying Cr film. Increasing the former increases the holding power. Increasing the latter increases the coercive force.

All of the above effects depend on the crystal orientation and surface condition of the underlying Cr film. Therefore, if it is possible to form a base Cr film that has both high crystal orientation and roughness,
Coercive force can be increased.

Although the above-mentioned high crystal orientation and roughness can be controlled to some extent by film forming conditions, it is extremely difficult to achieve both. For example, if you try to improve the crystal orientation of the underlying Cr film by lowering the Ar gas pressure under the film forming conditions,
The surface of the underlying Cr film becomes smooth, so the domain walls move easily (it becomes an n-type film. Conversely, if the Ar gas pressure is increased,
The column structure in the underlying Cr film becomes noticeable and can increase roughness, but the crystal orientation of the underlying Cr film decreases, resulting in insufficient orientation, which worsens the squareness ratio S, and as a result, the coercive force decreases. cannot be increased.

It is also possible to increase the coercive force by reducing the thickness of the magnetic film, but in this case the reproduction output will decrease, and as a countermeasure, it is necessary to extremely shorten the distance between the magnetic recording medium and the head. This makes quality control of the surface of the magnetic recording medium difficult and complicated.

The present invention has been made in view of these circumstances, and its purpose is to solve the above-mentioned problems of the conventional ones, and to solve the problems of the conventional ones. A magnetic recording medium in which the CR film has both high crystal orientation and roughness, the epitaxial assist effect and domain wall pinning effect of the magnetic film are excellent, and the magnetic properties such as coercive force and squareness ratio S are poor, that is, high density. The present invention aims to provide a recordable magnetic recording medium and a method for manufacturing the same.

(Means for Solving the Problems) In order to achieve the above object, a magnetic recording medium and a method for manufacturing the same according to the present invention have the following configuration.

That is, the method for manufacturing a magnetic recording medium according to the first aspect includes forming a first base layer having a rough surface on a substrate by sputtering, and forming a second base layer made of an amorphous film on top of the first base layer. Further, a third underlayer made of a highly crystal oriented film, a magnetic film made of a Co alloy, and a protective film made of C are formed in this order on the top layer by a sputtering method. This is the manufacturing method.

The method for manufacturing a magnetic recording medium according to claim 2 is characterized in that the first
The method for producing a Cl gas recording medium according to claim 1, wherein the underlayer is formed by sputtering a high melting point metal or a high melting point alloy.

In the method for manufacturing a magnetic recording medium according to the third aspect, the refractory metal or refractory alloy is Cr, Mo, WTa,
2. A method for manufacturing a magnetic recording medium according to claim 2, comprising one or more of Zr and Nb.

A magnetic recording medium according to a fourth aspect includes a substrate, a first underlayer having a rough surface, a second underlayer made of an amorphous film, a third underlayer made of a highly crystalline oriented film, and a Co alloy. This is a magnetic recording medium in which a magnetic film made of C and a protective film made of C are laminated in this order.

The magnetic recording medium according to the fifth aspect is the magnetic recording medium according to the fourth aspect, wherein the second underlayer is a C film or a SiO□ film.

(Function) As described above, the magnetic recording medium according to the present invention has
The first lower jlj which has a rough surface by sputtering method!
I try to form layers. Such a rough surface has an uneven surface, and as is known in the conventional method,
This can be obtained by increasing the Ar gas pressure in the sputtering method. Depending on the sputtering conditions such as gas pressure, the degree of the unevenness, that is, the roughness, can be increased. However, at the same time, the first underlayer has low crystal orientation.

After forming the first base layer, a second base layer made of an amorphous film is formed on the first base layer. Since this second underlayer is a thin film, it conforms to the surface shape of the first underlayer (tJ1 surface), and due to its influence, the surface of the second underlayer can be made similar to the surface shape of the first underlayer. 1st
As mentioned above, the underlayer has an uneven back surface. Therefore, the surface of the second base layer can be made to have a rough surface similar to the surface shape of the first base layer.

A third base layer made of a film with high crystal orientation is formed on the second base layer by sputtering. Such a highly crystalline oriented film can be produced by, as is known in the conventional method,
This can be obtained by lowering the Ar gas pressure in the spackling method. Since this third base layer is a thin film, the surface of the third base layer is made to have a rough surface similar to the surface shape of the first base layer for the same reason as when the surface of the second base layer can be made rough. obtain.

Regarding the crystal orientation of the third base layer, if the second base layer does not exist, the crystal orientation of the third base layer will be low due to the influence of the first base layer with low crystal orientation. . Also, even if the second underlayer exists, if it is not amorphous but crystalline, the first underlayer will still have an influence,
The crystal orientation of the third underlayer becomes low. In the present invention, since the second underlayer is an amorphous film as described above, the influence of the first underlayer having low crystal orientation can be prevented from reaching the third underlayer by the action of the upper film. up et al.
Regarding crystal orientation, the amorphous film of the second underlayer blocks the first underlayer and the third underlayer. Therefore, the third base layer can have both high crystal orientation and roughness.

On top of the third underlayer, Co
A magnetic recording medium is manufactured by forming a magnetic film made of an alloy and a protective film made of C on top of the magnetic film. As described above, the third underlayer can have both high crystal orientation and roughness, and this third underlayer serves as the underlayer of the magnetic film. Therefore, the epitaxial assist effect and domain wall pinning effect of the n-type film can be made excellent. Therefore, the manufactured magnetic recording medium can have excellent magnetic properties such as coercive force and squareness ratio S. In other words, a magnetic recording medium capable of recording at a density of 1.5 cm can be obtained.

It is desirable that the first underlayer be formed by sputtering a high melting point metal or a high melting point alloy. This is because the surface of the first underlayer formed by sputtering tends to be uneven, making it easier to obtain a t2 back surface with large roughness. Such high melting point metals or high melting point alloys include Cr,
It is desirable to use one or more of Mo, W, Ta, Zr, and Nb because they have a higher melting point.

By the above-described mounting method, a base plate, a first base layer having a tIi surface, a second base layer made of an amorphous film,
A magnetic recording medium is obtained in which a third underlayer made of a film with high crystal orientation, a magnetic film made of a Co alloy, and a protective film made of C are laminated in this order. For the reasons explained above, such a magnetic recording medium has excellent magnetic properties such as coercive force and squareness ratio S, and is capable of high-density recording.

The amorphous film of the second underlayer may be formed by sputtering or the like, or may be a naturally formed amorphous film. For example, if the first base layer is formed by sputtering and then taken out of the deposition chamber and exposed to the atmosphere, or if the first base layer is exposed to the atmosphere in the deposition chamber for a long time before forming the third base layer, Oxidation and gas adsorption occur on the surface of the underlayer, and an oxide film produced as a result of this or an amorphous film based on gas adsorption may be used. However, when forming the markings continuously, such as when an in-line sputtering apparatus for mass production is used, it is necessary to form the second underlayer by sputtering.

Regarding the above amorphous film composition, especially C film or SiO□
It is desirable to use a membrane. This is because the effect of blocking crystal orientation between the first underlayer and the third underlayer is large.

(Example) Examples of the present invention will be described below. The structures of the magnetic recording media according to Examples are as shown in FIG. 1, except for the conventional magnetic recording medium according to Example 6, which will be described later.
1) A first underlayer (2), a second underlayer (3), a third underlayer, that is, an underlayer Cr film (4), and a magnetic film made of a Co alloy (
5) and a C protective film (6) are formed in this order.

Month 1 Inoue: Cr film as the first underlayer, second layer on the glass substrate at room temperature.
A CII underlayer is formed, a Cr film is attached as a third underlayer, a Co alloy film is formed, and a C film is formed as a protective film in this order.
The Cr film was laminated to form a magnetic recording medium, and the effect of the thickness of the Cr film as the first underlayer on the magnetic properties was investigated.

The first base Cr film was formed at a total gas pressure of 20 mL, and the other films were formed at an Ar gas pressure of 1 mtorr.

The thickness of the second base layer is 50 people, and the thickness of the third base layer is 820 people.
The magnetic film used had a composition of Co-3ONi-7,5Cr, and its thickness was 600. The thickness of the protective film was 320 people.

The coercive force tic and the squareness ratio s, s'' are as shown in the third I, and in a magnetic recording medium that does not have a first underlayer film, it is llc:6.
00 to 7000e, but those with the first underlying Cr film suddenly have higher Ilc, and when the first underlying Cr film is 50
00 people reached 13000e, and the square ratio s,
s" is 0.9 or more.

A magnetic recording medium similar to that of Example 1 was manufactured under the same conditions as in Example 1 except for the thickness and thickness. That is, the thickness of the first base Cr film was 3,300 Å, the thickness of the second base layer was 50, and the thickness of the third base layer was varied to 1,640 Å or less. The magnetic properties of such magnetic recording media were measured, and the film thickness required as the CRV of the third underlayer was investigated. The results are shown in FIG.

The squareness ratio s, s'' is related to the thickness of the third underlying Cr film (,0,
The coercive force 11c is as high as 92 to 0.95, but the coercive force 11c is 2500e without the third underlayer, increases to 12000e when the third underlayer Cr film is 400 people thick, and remains constant at thicknesses beyond that. It has become.

The role of the third base Cr film is to make the 6n film into a hap structure and give it crystal orientation, and it has been found that this can be achieved by increasing the thickness of the third base Cr film to 400 Å or more. .

In a magnetic recording medium with a conventional structure, if the thickness of the underlying Cr film of the magnetic film is increased, the surface roughness of the underlying Cr film, which is one of the requirements for increasing the coercive force 11c, increases. , Ilc have a gradual upper bound. In contrast, in this embodiment, even if the thickness of the third base Cr1l increases as described above, H
c is constant. This is because the first underlying Cr film at the bottom plays the role of surface roughness, so even a very thin Cr film can
lc is constant.

An AI substrate with N1-P plating was used as the main substrate, and a Mo film was used as the first underlayer. Except for these points, a similar magnetic recording medium was manufactured under the same conditions as in Example 1, and the influence of Mo of the first underlayer and the thickness of the film on the magnetic properties was investigated.

Hc, S, S'' are as shown in Fig. 5, and as expected, llc increases dramatically with increasing thickness of the first base Mo film.When the gate 0 film thickness is 4000, llc is about 14000.
e, and the squareness ratios S and S'' are 0.95.

The thickness of the first base layer of backyard mottled Cr film was 3300, and the magnetic film (Co-3
The thickness of ONi7.5Cr) was varied from 100 to 1000. Except for these points, a similar magnetic recording medium was manufactured under the same conditions as in Example 1, and the influence of the magnetic film thickness on the magnetic properties was investigated.

Figure 6 shows the relationship between the magnetic film thickness and Hc, S, S". For 400 to 800 people with a magnetic film thickness of 400 to 700 G tt tn as liver δ, and llc of 1000 to 700.
15000e, S, S'' is a high value of 0.95 or more.

4,000 people of Cr, Mo, W, Ta formed the first base layer
, Zr or Nb film. Example 1 except for this point
A similar magnetic recording medium was manufactured under the same conditions as above, and llc and S were examined. The results are shown in FIG.

The first base layer is composed of high melting point metal,
Among them, there is a tendency that the higher the melting point of the metal, the higher the llc. S is almost 0.93 in both cases.
~0.96, which is a high value.

A comparative test was conducted between a magnetic recording medium according to the conventional method and a magnetic recording medium according to the present invention.

Table 1 shows the configuration and manufacturing conditions of the magnetic recording medium used in the above test. In Table 1, Experiment Nos. 1 and 2 are related to the present invention, and Experiment No. 3 is related to the present invention.

Items 4 and 5 are related to the conventional method.

In the device according to the present invention, a glass substrate or an AI substrate plated with N1-P was used as the substrate. The first underlayer is a Cr film or a Mo film, and the film thickness is 5.
It was varied within a range of 000 Å or less. The magnetic film thickness was 500. Except for this point, the structure is similar to that of Example 1. The manufacturing conditions are the same as in Example 1.

In the conventional method, a glass substrate was used as the substrate, and the thickness of the underlying Cr film was varied in the range of 1000 to 5000. The magnetic film thickness was 500.

Incidentally, these naturally have a first underlayer and a second underlayer, and the underlayer is only the above-mentioned underlayer Cr film.

The comparative test results are shown in Figure 8. The horizontal axis indicates the thickness of the underlying Cr film, which in the case of the invention relates to the Cr film thickness of the third underlying layer (Table 1 Note) Formation of the first underlying layer. Ar gas pressure during film: 20 mto
It is rr. As can be seen from FIG. 9, in the conventional method, even if the thickness of the underlying Cr film was increased, llc: 10000e
No material satisfying the above conditions and S: 0.9 or more was obtained. On the other hand, in the case of the present invention, when the third base Cr film thickness is set to 1000, llc is LOOOOe or more and S is 0.94 to 0.96.

The above results confirm that the present invention can provide a magnetic recording medium that has both a high coercive force and a high squareness ratio S.

(Effect of the invention) According to the magnetic recording medium and the manufacturing method thereof according to the present invention,
The underlying Cr film of the magnetic film has both high crystal orientation and roughness, and has an excellent Evita kinial assist effect and E
A magnetic recording medium having an excellent n-wall pinning effect and excellent magnetic properties such as coercive force and squareness ratio S, that is, a magnetic recording medium capable of high-density recording can be obtained.

[Brief explanation of drawings]

FIG. 1 shows the structure of the 6D magnetic recording medium according to the example, FIG. 2 shows the structure of the conventional magnetic recording medium, and FIG. 3 shows the thickness of the first underlying Cr film and the thickness of the first base Cr film according to the example 1. FIG. 4 shows the relationship between the thickness of the third base Cr film and Hc according to Example 2.
, S, S'', FIG. 5 shows the relationship between
The relationship between the thickness of the underlying Mo film and Ilc, S, S'',
FIG. 6 shows the if film thickness according to Example 4! Ic, SS
1, FIG. 7 shows the relationship between the melting point of the metal of the first underlayer and Hc, S according to Example 5, and FIG. 8 shows the relationship between the underlying Cr film thickness and llc, S according to Example 6. FIG.

Claims (5)

[Claims] (1) A first base layer having a rough surface is formed on the substrate by a sputtering method, a second base layer made of an amorphous film is formed on top of the first base layer, and a highly crystalline oriented film is further formed on the top layer by a sputtering method. A method for manufacturing a magnetic recording medium, which comprises forming in this order a third underlayer made of . (2) The method for manufacturing a magnetic recording medium according to claim 1, wherein the first underlayer is formed by sputtering a high-melting point metal or a high-melting point alloy. (3) The high melting point metal or high melting point alloy is Cr, Mo,
A second layer consisting of one or more of W, Ta, Zr, and Nb
A method for manufacturing a magnetic recording medium according to the claims. (4) a substrate, a first underlayer having a rough surface, a second underlayer made of an amorphous film, a third underlayer made of a highly crystalline oriented film, a magnetic film made of a Co alloy, and a C A magnetic recording medium in which a protective film is laminated in this order. (5) The magnetic recording medium according to claim 4, wherein the second underlayer is a C film or a SiO_2 film.