JPH07111775B2 - Magnetic recording medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium having a recording magnetic layer having perpendicular magnetic anisotropy.

[Technical background of the invention and its problems]

In recent years, with the development of information processing technology, the amount of information carried by a memory device has dramatically increased, and there has been an increasing demand for larger capacity of magnetic recording media such as floppy disks. In order to meet this demand, research on magnetic recording media capable of high-density recording, in particular, magnetic recording media for perpendicular magnetic recording, which records by utilizing magnetization perpendicular to the film surface.
Development is active. A magnetic recording medium for perpendicular magnetic recording is a medium having a recording magnetic layer having perpendicular magnetic anisotropy, and is more than a coating type medium that constitutes most of the magnetic recording media for in-plane recording currently in practical use. In addition, a metal thin film type medium in which a metal thin film such as a Co-cr alloy is formed by sputtering or vapor deposition as a recording magnetic layer, or an oxide thin film type medium having a magnetoplumbite type crystal structure such as Ba ferrite or Sr ferrite is high. It is regarded as a promising medium for density recording.

By the way, in the coating type medium, since the recording magnetic layer is formed by mixing magnetic powder with a binder or the like and coating it on the substrate, the recording magnetic layer has elasticity, and a lubricant is mixed in the magnetic layer. It is also possible to maintain good contact between the medium and the magnetic head and to obtain sufficient durability of the medium and the head.

On the other hand, in a metal thin film type medium or an oxide thin film type medium, since the recording magnetic layer has almost no elasticity, when a magnetic head made of a hard material such as ferrite runs on the medium, the medium surface or the surface of the head It is easy for scratches and other damage to occur. In that case, not only the durability of the medium and the head is impaired, but also the effective distance between the medium and the head is increased due to the adherence of the abrasion powder of the medium and the head, and the spacing loss is increased. Cause deterioration of the output, decrease in output during playback, and output fluctuation.

Therefore, in the case of a metal thin film type medium or an oxide thin film type medium, it is conceivable to form a protective layer made of a hard material on the recording magnetic layer to protect it. As specific examples of the protective layer, thin films of silicon oxide, aluminum oxide, titanium nitride and the like have been conventionally proposed. However, these hard protective layers are fragile in material, and also easily wear due to contact with the magnetic head, and the abrasion powder damages the medium and the head, so it is not sufficient as a solution to the above-mentioned problems. Is.

In this case, a thick protective layer is considered to be effective in preventing at least the wear of the recording magnetic layer, but it is not preferable in terms of perpendicular magnetic recording characteristics. That is, the perpendicular magnetic recording method has a recording density much higher than that of the in-plane magnetic recording method, and the recording wavelength can be shortened. For that purpose, the effective distance between the head and the medium is extremely small. The thickness of the protective layer is therefore limited. If the thickness of the protective layer is suppressed to such an extent that the perpendicular magnetic recording characteristics are not impaired, the effect of improving durability cannot be expected so much.

[Object of the Invention]

An object of the present invention is to maintain the perpendicular magnetic recording characteristics,
It is an object of the present invention to provide a magnetic recording medium that can remarkably enhance the durability of the medium itself and the magnetic head that travels in contact with the medium.

[Outline of Invention]

The magnetic recording medium according to the present invention contains silicon, nitrogen and oxygen on the recording magnetic layer having perpendicular magnetic anisotropy, and has a wavelength of λ /, where 1 / λ (wave number) is 850 ^−1. c
It is characterized in that an amorphous thin film showing an infrared absorption maximum in a range of m or more and 1050 ^-1 cm or less is formed.

〔The invention's effect〕

According to the present invention, since the Si—N—O type thin film containing an appropriate amount of oxygen is formed as the protective layer, it is possible to obtain a magnetic recording medium having excellent durability and good perpendicular magnetic recording characteristics.

That is, since the Si—N—O type thin film containing an appropriate amount of oxygen has a Vickers hardness of about 1300 kg / m ² and is extremely hard, the recording magnetic layer is surely protected from damage due to contact with the magnetic head. It is possible to protect. Moreover, the Si—N—O type thin film has excellent wear resistance as compared with a thin film of silicon oxide, aluminum oxide, titanium nitride or the like. Therefore, even if the magnetic head continuously runs on this Si—N—O type thin film, the generation of abrasion powder is very small, and the abrasion and damage of the medium itself and the head are greatly reduced. Furthermore, since this Si-NO thin film is extremely dense in material,
It has an effect of blocking the recording magnetic layer from the outside air and remarkably improving the corrosion resistance. This effect is particularly exerted on the above-mentioned Si-NO
It is more remarkable when the system thin film is amorphous. This Si-N
Since the -O-based thin film has the excellent wear resistance and corrosion resistance described above, it is possible to improve the durability of the medium and the magnetic head even if the film thickness is relatively thin. Therefore, as described above, the generation of wear particles is small and the increase in the effective distance between the medium and the head due to the wear particles is small, and the spacing loss between the medium and the head can be reduced, and the frequency characteristic It is possible to improve the characteristics and reduce the output decrease and the output fluctuation during the reproduction, and it is possible to dramatically improve the perpendicular magnetic recording characteristics. That is, it is possible to provide a magnetic recording medium that satisfies both durability and perpendicular magnetic recording characteristics at the same time.

Further, in the present invention, particularly, the Si—N—O type amorphous thin film which is the protective layer is constituted so as to exhibit the infrared absorption maximum in the range of 1 / λ of 850 ⁻¹ cm or more and 1050 ⁻¹ cm or less. By
This has the effect of significantly improving durability. That is,
In general, the bonding state of an amorphous thin film cannot be specified by the composition ratio of the constituents of the film (in the case of the protective layer of the present invention, the composition ratio of Si-N and O), but the absorption maximum of infrared rays is maximized. Can be represented by a wavelength that indicates the absorption layer of infrared rays.
It is possible to know the bonding state of the Si—N—O type amorphous thin film. When an amorphous thin film such as a Si—N—O type amorphous thin film is used as the protective layer, the abrasion resistance, that is, the durability as a magnetic recording medium is greatly influenced by the bonding state.

Therefore, it was examined Si-N-O based wavelength showing an absorption maximum in the infrared amorphous thin film, i.e., the bonding state while varying the durability as a protective layer, 1 / lambda is 850 ^{- 1} c
When the Si—N—O type amorphous thin film is formed so as to exhibit the infrared absorption maximum in the range of m or more and 1050 ⁻¹ cm or less,
The durability is remarkably improved as compared with a thin film having a composition different from that of the N—O type amorphous thin film or a Si—N—O type amorphous thin film having a wavelength of infrared absorption maximum not within this range. It was a finding.

Example of Invention

FIG. 1 is a sectional view showing a magnetic recording medium according to an embodiment of the present invention. In the figure, a substrate 1 is a resin film substrate, and a recording magnetic layer is formed on both surfaces of the substrate 1 by, for example, DC magnetron sputtering to form a C film having a thickness of 0.5 μm.
Each of the o-Cr alloy thin films 2 is formed. This Co
The --Cr alloy thin film 2 is oriented so that it has an easy axis of magnetization in the direction perpendicular to the film surface. That is, Co-Cr alloy thin film 2
Has perpendicular magnetic anisotropy. And, as a protective layer on the Co-Cr alloy thin film 2, 20-500Å, more preferably 50
The Si—N—O based thin films 3 each containing an appropriate amount of oxygen with a thickness of about 400 Å are formed.

The Si—N—O type thin film 3 is formed by high frequency sputtering using a silicon nitride target, for example. In this case, the sputtering vacuum chamber was evacuated to about 10 ^-7 Torr in advance, the residual impurity gas was sufficiently removed, and then argon gas and oxygen gas were introduced up to about 10 ^-2 to perform sputtering. In addition, reactive sputtering using a silicon target can also be used for forming the Si—N—O based thin film 3. The proportions of silicon, nitrogen, oxygen and other impurities in the Si—N—O type thin film 3 are
It is controlled by the film forming speed, the oxygen partial pressure of the sputtering gas pressure, and the like. The Si—N—O type thin film 3 thus formed is generally amorphous, has good compatibility and adhesion with the Co—Cr type alloy thin film 2, and is very hard and hard to wear. Therefore, even when the magnetic head continuously contacts the medium like a floppy disk and runs, extremely high durability can be obtained.

Table 1 shows the results of an experiment for examining the durability of magnetic recording media in which various protective layers were formed on a Co-Cr alloy thin film by high frequency sputtering. However, in the experiment, the magnetic recording medium having the above-mentioned structure was produced in the form of a floppy disk, and the ferrite magnetic head was brought into contact with the same track on the disk while the disk was rotated at 300 rpm. Here, the durability is the number of times of travel (pass) until at least one of the medium (disk) and the head is significantly damaged. In the case of a medium, the term “significant damage” refers to a state in which at least a part of the protective layer and the recording layer are displaced and the surface of the substrate is exposed. Also,
In Table 1, Examples 1 to 5 and Comparative Examples 1 and 2 are all made of Si.
Although the -NO system thin film was used as the protective layer, the durability was examined for various layers having different reciprocal 1 / λ (wave number) of the wavelength showing the infrared absorption maximum. This 1 / λ depends on the bonding state of the Si—N—O type thin film, and the durability of the magnetic recording medium, that is, Si−
The wear resistance of the N—O type thin film is greatly influenced by this bonded state. The ratio of silicon, nitrogen and oxygen of the thin film 3 is the same as that of a silicon nitride thin film containing oxygen.
At the same time as being formed on the Co-Cr alloy thin film, it was also formed on the silicon wafer under the same conditions.
It was determined by infrared absorption spectrum and Auger electron analysis.

As is clear from Table 1, silicon based on the present invention is used.
Contains Si, nitrogen N and oxygen O, and ¹ λ is 850 ^-1 cm
As described above, the magnetic recording medium formed as the protective layer of the amorphous thin film configured to exhibit the infrared absorption maximum in the range of 1050 ^-1 cm or less shows excellent characteristics in durability, As compared with the thin films of silicon nitride, aluminum oxide, tungsten carbide, boron nitride, titanium nitride, etc., which have been proposed as above, the durability is remarkably improved although the film thickness is thinner. Needless to say, the Si—N—O-based thin film may contain incidental impurities in addition to silicon, nitrogen, and oxygen.

Further, according to the above embodiment, the recording magnetic layer is the Co—Cr based alloy thin film 2, and the Si—N—O based thin film 3 is formed on the recording magnetic layer. Therefore, the Co—Cr based alloy thin film is formed. Since the Cr component in 2 contributes to the improvement of the adhesiveness with the Si—N—O type thin film 3, good adhesion of the Si—N—O type thin film 3 can be obtained without interposing an intermediate layer. Therefore, as described above, in combination with the fact that the Si—N—O based thin film 3 itself may be thin, the effective distance between the medium and the head can be reduced more effectively, and even in perpendicular magnetic recording There is an advantage that pacing loss is very small and good recording and reproducing characteristics can be obtained.

FIG. 2 shows a magnetic recording medium according to another embodiment of the present invention, in which a soft magnetic underlayer 12 is formed on a non-magnetic substrate 11 by vapor deposition.
And a Co—Cr based alloy thin film 13 as a recording magnetic layer is laminated and a Si—N—O based thin film 14 as a protective layer is formed thereon by sputtering. For the soft magnetic underlayer 12, for example, a permalloy thin film, a Co—Zr alloy thin film, a sendust alloy thin film, or the like is used.

Also in the magnetic recording medium having such a structure, excellent perpendicular magnetic recording characteristics and high durability can be obtained as in the magnetic recording medium described in the above embodiment.

FIG. 3 shows a magnetic recording medium according to still another embodiment of the present invention. In the magnetic recording medium shown in FIG.
As the lubricating layer 4, for example, a fluorocarbon-based liquid lubricating layer is applied and formed on the NO thin film 3.

In the magnetic recording medium of this embodiment, especially Si--N--O
Since the system amorphous thin film 3 is excellent in the wettability and the protective ability of the lubricating layer 4 made of a fluorocarbon lubricant, the lubricating layer 4 is applied to a thin and uniform thickness so as not to impair the perpendicular magnetic recording characteristics. can do. In addition, Si-NO-based thin film 3
A sufficient bonding force between the lubricating layer 4 and the lubricating layer 4 can be obtained.

Table 2 shows the results of examining the relationship between durability and various combinations of materials of the protective layer and the lubricating layer formed on the Co—Cr alloy thin film.

As shown in Table 2, Si-N containing an appropriate amount of oxygen
In the magnetic recording medium according to the present invention in which a fluorocarbon lubricating layer is formed as a lubricating layer on the --O thin film, the Si--N--O thin film and the lubricating layer which are protective layers have a thin thickness suitable for perpendicular magnetic recording. While suppressing the above, a conventional magnetic recording medium using an aluminum oxide film, a tungsten carbide film or the like as a protective layer (Comparative Examples 3 to 9), or 1 / λ showing an infrared absorption maximum of 850 ^-1 cm or more, 1050 ^{-Medium in} which a lubricating layer is formed on a Si-NO-based thin film that is not within the range of ^-1 cm or less (Comparative Example
It is clear that the durability is markedly improved as compared with 1, 2).

The present invention is not limited to the above embodiment,
Various modifications can be made without departing from the spirit of the invention. For example, although Co-Cr alloy thin film was illustrated as the recording magnetic layer in the examples, other than Co-Cr alloy thin film may be used as long as it has perpendicular magnetic anisotropy. Not limited to this, a metal oxide thin film may be used. Further, in the embodiment, the recording magnetic layer and the protective layer are provided on both surfaces of the substrate,
Further, although the magnetic recording medium in which the lubricating layer is formed has been described, the present invention can be applied to a medium in which these are formed only on one surface.

[Brief description of drawings]

1 is a sectional view of a magnetic recording medium according to an embodiment of the present invention, FIG. 2 is a sectional view of a magnetic recording medium according to another embodiment of the present invention, and FIG. 3 is another embodiment of the present invention. 3 is a cross-sectional view of a magnetic recording medium according to an example. FIG. 1 ... Resinous film substrate, 2 ... Co-Cr alloy thin film (magnetic recording layer), 3 ... Si-NO system thin film, 4 ... Lubrication layer, 11 ... Non-magnetic substrate, 12 ... ... Co-Cr alloy thin film (recording magnetic layer), 13 ... Si-NO thin film.

Claims (4)

[Claims] 1. A magnetic recording medium provided with a recording magnetic layer having perpendicular magnetic anisotropy, wherein the recording magnetic layer contains silicon, nitrogen and oxygen and the wavelength is λ.
A magnetic recording medium comprising an amorphous thin film having an infrared absorption maximum in a range of 1 / λ of 850 ^-1 cm or more and 1050 ^-1 cm or less. 2. The magnetic recording medium according to claim 1, wherein the recording magnetic layer is a Co—Cr alloy thin film. 3. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is a floppy disk. 4. The magnetic recording medium according to claim 1, further comprising a lubricating layer formed on the amorphous thin film.