JPH0512646A - Perpendicular magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the magnetic recording medium having a high coercive force by incorporating a prescribed ratio of carbon into a magnetic metallic thin film essentially consisting of Co and Cr. CONSTITUTION:This perpendicular magnetic recording medium is constituted by forming the C-contg. Co-Cr alloy film 102 as a magnetic layer on a nonmagnetic base 101 and forming a protective film 103 consisting of the carbon thereon. The Co-Cr alloy film 102 contains 0.05 to 2.0wt.% carbon. Further, the protective film 103 formed on this magnetic metallic thin film 102 is formed of the carbon having 30 400Angstrom thickness. The carbon is added to the Co-Cr alloy film 102 in such a manner, by which the substrate temp. at the time of film formation is set low and such film is advantageous for production. In addition, noises can be decreased. The remarkable improvement in sliding durability is possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a perpendicular magnetic recording medium having a CoCr system perpendicular magnetization film as a magnetic layer.

[0002]

2. Description of the Related Art In the field of magnetic recording, higher density is required year by year, and a magnetic recording medium to be used is formed by coating a magnetic oxide with a binder in accordance with this, and a metal magnetic thin film is used as a magnetic layer. It is shifting to a metal thin film type medium that can Also, the recording method is different from the so-called in-plane magnetic recording method that uses a magnetic recording medium having an easy axis of magnetization in the plane to the perpendicular magnetic recording medium that uses a magnetic recording medium having an easy axis of magnetization in the direction perpendicular to the film surface. It is expected that the recording system will be changed. The perpendicular magnetic recording method has a feature that when it is recorded at a high density, the demagnetization effect is extremely small compared to the in-plane magnetic recording method, and the magnetization is stable. By adopting such a method, the recording density is dramatically increased. It is possible to increase.

By the way, the magnetic layer of the magnetic recording medium used in this perpendicular magnetic recording system is mainly a Co--Cr alloy film, which is formed by a sputtering method or a vacuum evaporation method. Here, C is formed by either the sputtering method or the vacuum deposition method.
Even when an o-Cr alloy film is formed, a certain degree of coercive force Hc (for example, 700 oersted = 56 kA / m or more)
In order to ensure the above, it is necessary to raise the substrate temperature during film formation to a high temperature of about 200 ° C. or higher.

However, when the substrate is heated to a high temperature as described above, in addition to the problem of so-called cupping and wrinkling, there is a problem that the film forming apparatus is curled due to thermal deformation or the like. In consideration of the production of, it is preferable that the film can be formed at a temperature as close to room temperature as possible.

On the other hand, in terms of sliding durability, Co-
A perpendicular magnetic recording medium having a Cr alloy film as a magnetic layer is also a metal thin film type magnetic recording medium, and therefore its improvement is a major problem. Therefore, it is essential to select a protective film suitable for this.

[0006]

As described above, Co-
In a perpendicular magnetic recording medium having a Cr alloy film as a magnetic layer, it is desired to lower the substrate temperature when forming a Co—Cr alloy film as much as possible and to ensure sliding durability.

Therefore, the present invention has been proposed in view of such conventional circumstances, and it is possible to lower the substrate temperature at the time of forming a magnetic layer, which is excellent in magnetic characteristics such as coercive force and causes noise. An object is to provide a small number of perpendicular magnetic recording media. A further object of the present invention is to provide a perpendicular magnetic recording medium having excellent sliding durability by selecting a protective film suitable for a Co-Cr alloy film.

[0008]

Means for Solving the Problems As a result of intensive studies by the present inventors, it was found that Co-Cr was not achieved.
By adding carbon (C) to the alloy film, the substrate temperature at the time of film formation can be lowered, and further, the Co-Cr alloy film to which carbon is added has good compatibility with the carbon protective film and has good sliding durability. We have found that it will be greatly improved. The present invention has been completed based on the above findings, and a metal magnetic thin film mainly composed of Co and Cr and containing 0.05 to 2.0% by weight of carbon is formed as a magnetic layer on a non-magnetic support. A carbon protective film having a thickness of 30 to 400Å is formed on the metal magnetic thin film.

That is, the perpendicular magnetic recording medium of the present invention is
As shown in FIG. 1, C-containing Co is formed on the non-magnetic support 101.
While forming the -Cr alloy film 102 as a magnetic layer,
The protective film 103 made of carbon is formed. Here, the C-containing Co—Cr alloy film 10 that is the magnetic layer
No. 2 contains Co and Cr as the main components, but its composition may be within a range in which the Co-Cr alloy sufficiently functions as a magnetic material, and Cr is usually 0 to 25% by weight.

Further, in the present invention, carbon (C) is added to the Co-Cr alloy film to form the C-containing Co-Cr alloy film 102, and sufficient magnetic characteristics can be obtained even when the substrate temperature during film formation is low. In particular, ensure coercive force. At this time, the amount of carbon added is preferably 0.05 to 2.0% by weight, and more preferably 0.05 to 0.5% by weight. The amount of carbon added is 0.05
If it is less than wt%, a sufficient effect cannot be obtained, and conversely, if the amount of carbon added exceeds 2.0 wt%, the magnetic properties, especially the perpendicular magnetic anisotropy, may deteriorate.

On the other hand, the C-containing Co--Cr alloy film 102 described above.
The protective film 103 formed above is made of carbon and plays a role of significantly improving sliding durability. As the protective film 103, various materials such as SiO ₂ can be considered, but a carbon film is most suitable for the protective film of the C-containing Co—Cr alloy film, and the protective film 103 made of carbon should be formed. It was found that the sliding durability can be greatly improved by.

When forming the protective film 103 made of carbon, it is important to select the film thickness.
Å When the film thickness of the protective film 103 is less than 30Å, it does not become a continuous film and sufficient sliding durability cannot be secured. When the thickness of the protective film 103 exceeds 400 Å,
The spacing halves the output, especially in the short wavelength range.
A film made of various lubricants may be formed on the surface of the protective film 103 for the purpose of improving runnability.

[0013]

When carbon (C) is added to the Co-Cr alloy film, the magnetic characteristics, especially the coercive force Hc can be enhanced even if the substrate temperature during film formation is low. Also, carbon-added Co-C
The r alloy film is well compatible with the carbon protective film, and the sliding durability is significantly improved by forming the carbon protective film having a film thickness within a predetermined range.

[0014]

EXAMPLES Specific examples to which the present invention is applied will be described in detail below with reference to the drawings and experimental results.

First, in this example, a C-containing Co-Cr perpendicular magnetic recording medium was manufactured using a continuous sputtering apparatus as shown in FIG. In this sputtering apparatus, a can roll 2 is arranged substantially in the center of the vacuum chamber 1, and a winding roll 3 and a winding roll 4 are arranged above the can roll 2. Therefore, the base film B is sent out from the unwinding roll 3 to the can roll 2, and travels along the can roll 2 to form a Co—Cr alloy film, and then is wound around the winding roll 4. ..

On the other hand, at the position below the can roll 2, C
A target made of an o-Cr alloy and a target made of carbon (collectively referred to as the target 5) are arranged to face each other, and in the vicinity of the can roll 2, to regulate the incident angle of particles flying from the target 5. A pair of masks 6 and 7 and a thermocouple 8 are installed. Therefore, the C-containing Co—Cr alloy film is formed in a direction substantially perpendicular to the base film B.

In this embodiment, the base film B is a polyimide film having a heat resistance of 300 ° C. or higher and a thickness of 40 μm. The sputtering conditions are as follows. First, the outgassing temperature of the base film B is 150 ° C. and the back pressure P _b = 3 × 10 ⁻⁶ Torr (= 4 × 10).
^-4 Pa), Argon pressure P _Ar = 1mTorr (= 0.13P)
a).

As the target 5, a carbon chip was placed on a Co-Cr target (Cr content 21% by weight) in an area ratio of 0.5 to 5%, and the input power was 2 kW (6
DC magnetron type sputtering was performed at a voltage of 00 V × 3.3 A). The distance between the base film B and the target 5 is 70 mm, and the film forming speed is 2000 Å / min. The feed rate of the base film B is 15 cm / min, and the C-containing Co-
The Cr alloy film was formed to have a film thickness of 2000 liters.

According to the method described above, various C-containing Co-Cr alloy films are formed by changing the amount of carbon added, a protective film is formed, and a lubricant is applied to the surface of the film to prepare various samples. did. Co-C in the prepared sample
Table 1 shows the composition of the r alloy film, the type of the protective film, and the film thickness.

[0020]

[Table 1]

Next, with respect to these samples, the substrate temperature required to obtain a coercive force Hc of 1000 (Oe), the perpendicular magnetic anisotropy Hk _eff , the relative output when a signal having a wavelength of 0.5 μm was recorded and reproduced, and sliding. The durability was checked. The perpendicular magnetic anisotropy Hk _eff is the vibration sample magnetometer (VSM).
It was determined from the inclination of the M-H loop in the in-plane direction measured using. Relative output, linear velocity 3m / sec, track width 20
The measurement was performed using a metal-in-gap type magnetic head having a size of μm, a gap length of 0.25 μm, and a depth of 20 μm. The sliding durability was defined as the number of passes from the initial value to -3 dB. The results are shown in Table 2.

[0022]

[Table 2]

As is apparent from Table 2, the substrate temperature can be lowered by 40 ° C. or more by adding carbon to the Co—Cr alloy. However, as is apparent from Comparative Example 3, when the amount of carbon added is too large, the perpendicular magnetic anisotropy deteriorates. In addition, Comparative Example 2
As is clear from the above, the sliding durability is extremely poor only with the addition of carbon, and a protective film is required.

Then, in order to compare the performance of the protective film, comparing each Example with Comparative Examples 4 to 5, the sliding durability is greatly improved when carbon is used as the protective film.
On the other hand, when SiO ₂ or Co—O is used as the protective film, some improvement can be seen, but the durability is worse than that of carbon. Regarding the film thickness of the protective film, when the film thickness is too large as in Comparative Example 6, the output is reduced.

Although the specific embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and various modifications can be made without departing from the gist of the present invention. Needless to say. For example, although the C-containing Co—Cr alloy film was formed by the sputtering method in the above-mentioned embodiment, the vacuum vapor deposition method may be adopted.

[0026]

As is clear from the above description, in the present invention, since carbon is added to the Co-Cr alloy film, the substrate temperature at the time of film formation can be set at a low level, which is advantageous in manufacturing. It is very advantageous, and noise and the like can be reduced. Further, in the present invention, C-containing C
Since the carbon protective film, which is a protective film suitable for the o-Cr alloy film, is formed on the magnetic layer, the sliding durability can be significantly improved.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of essential parts showing an example of a perpendicular magnetic recording medium to which the present invention is applied.

FIG. 2 is a schematic diagram showing a configuration example of a continuous sputtering apparatus.

[Explanation of symbols]

 101 ... Non-magnetic support 102 ... C-containing Co—Cr alloy film 103 ... Carbon protective film

Claims (1)

Claim: What is claimed is: 1. A metal magnetic thin film containing Co and Cr as a main component and containing carbon in an amount of 0.05 to 2.0% by weight is formed as a magnetic layer on a non-magnetic support. A perpendicular magnetic recording medium characterized in that a carbon protective film having a thickness of 30 to 400 Å is formed on a magnetic thin film.