JPH0830949A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To enhance coercive force, to reduce noise and to obtain a magnetic recording medium fit for high density recording by interposing a metallic intermediate film for controlling the fine structure of an under film between a glass substrate and the under film. CONSTITUTION:A metallic intermediate film 12 of Cr for controlling the fine structure of an under film 13 is interposed between a glass substrate 11 and the under film 13 of Cr, etc., and a magnetic film 14 consisting of 7-12at.% Cr, 18-28at.% Ni and the balance Co with inevitable impurities is formed on the under film 13. The intermediate film 12 affects the crystal growth of the films 13, 14 laminated in succession, enhances the coercive force of the magnetic film 14 by controlling the fine structure of the film 14 and reduces noise. The thickness of the intermediate film 12 is preferably regulated to 50-500Angstrom so as to bring the under film 11 into crystal growth favorable for the production of the objective magnetic recording medium fit for high density recording.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium used in a magnetic disk device for recording information, and more specifically, it has an improved underlayer under the magnetic layer and has a C layer on a glass substrate.
This is a laminate of oNiCr so that a high coercive force can be obtained.

[0002]

2. Description of the Related Art Cr, W, Mo or an alloy film containing them as a main component is formed as a base film on a non-magnetic substrate by a method such as a sputtering method, and Co-Cr-Ta, C is formed on the base film.
A magnetic recording medium having an alloy film such as o-Ni-Cr or Co-Cr-Pt formed is currently used as a magnetic recording medium capable of high density recording. In magnetic disk devices for computers, there is a strong demand for large capacity in recent years.
In order to increase the capacity, it is necessary to increase the recording density of the magnetic recording medium. In order to increase the recording density, a substrate having a smooth surface to enable the flying height of the magnetic head to be lowered, and a high coercive force of the magnetic recording medium,
Low noise is required. By the way, conventionally, a NiP-plated aluminum substrate has been used as a magnetic recording medium substrate, but in recent years, a glass substrate has attracted attention as a magnetic disk substrate. A glass substrate has attracted attention as a substrate for a high-density magnetic disk because it has excellent surface smoothness, is hard, has a large deformation resistance, and has few surface defects (for example, JP-A-49-122707).
JP-A-52-18002). The structure of the magnetic recording medium is
When using an aluminum substrate plated with NiP, Cr
CoCrTa, CoNiPt, CoCr on the underlying film such as
A magnetic film of Pt, CoNiCr or the like and a protective film of C, SiO 2 or the like are sequentially laminated. When a glass substrate is used, a coercive force is lower than when an aluminum substrate is used when an underlayer film is directly formed on the glass substrate as in the case of an aluminum substrate, and a magnetic film and a protective film are sequentially laminated. In order to obtain the same coercive force, it is necessary to increase the thickness of the underlayer film. In view of this, Japanese Patent Laid-Open No. 29923/1990 discloses a nonmagnetic intermediate film provided between a glass substrate and a base film to contain gas released from the glass substrate to improve magnetic properties.

[0003]

However, the magnetic recording medium disclosed in the above prior art has the advantage that the coercive force of the magnetic layer can be increased without increasing the thickness of the underlayer. The coercive force is about 1100 Oe to 1390 Oe as disclosed in the above-mentioned publication, and there is a problem that it does not always meet the requirement as a magnetic recording medium required to have a high coercive force. Therefore, the present invention is directed to CoN of a magnetic recording medium using a glass substrate.
The purpose of the present invention is to provide a magnetic recording medium suitable for high-density recording by examining the composition, magnetic characteristics, and recording / reproducing characteristics of the iCr alloy magnetic film, increasing coercive force, reducing noise.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted earnest research on the composition and manufacturing conditions of a CoNiCr magnetic film alloy using a glass substrate in order to improve magnetic characteristics and recording / reproducing characteristics, and completed the present invention. It was The present invention provides a magnetic recording medium having a metal intermediate film made of Cr for controlling the fine structure of an underlayer between a glass substrate and an underlayer of Cr or the like. A magnetic recording medium comprising 18 at% or more and 28 at% or less Ni, the balance Co, and inevitable impurities. The reason for providing the metal intermediate film made of Cr is as follows. The magnetic characteristics and recording / reproducing characteristics of the magnetic film depend on the fine structure such as the crystal grain size and orientation of the magnetic film. The crystal growth of the magnetic film changes due to the crystal growth of the underlayer film. Therefore, in order to produce a magnetic film having excellent magnetic characteristics and recording / reproducing characteristics, the crystal structure of the underlayer must be improved. When the metal intermediate film made of Cr is provided on the glass substrate, the substrate temperature rises as compared with the case where the Cr intermediate film is not provided at the time of heating the substrate. Further, when the Cr intermediate film is provided, since the same material as the Cr underlayer film is used, more uniform crystal growth can be performed than when the Cr underlayer film is directly formed on the glass surface. By using the Cr intermediate film as described above,
When sequentially stacked on top of it, it influences the crystal growth of the underlying film and the magnetic film, it becomes possible to control the fine structure of the magnetic film, the coercive force of the magnetic film can be increased, and the noise can be reduced. . Further, in the above magnetic recording medium, in order to conveniently perform crystal growth of the Cr underlayer in order to obtain a magnetic recording medium suitable for high density recording, the thickness of the Cr metal intermediate film should be 50 A or more and 500 angstroms or less. Is desirable. If the thickness of the metal intermediate film is thinner than 50 Å, it becomes difficult to control the crystal growth of the underlayer and the magnetic film, and if it is thicker than 500 Å, the grain size of the underlayer becomes large, which is not preferable. The reason why the composition of the magnetic film is set to the above is as follows. Since Cr has the effect of increasing the coercive force of the alloy, it is 7a.
Contains t% to 12 at%. If the Cr content is less than 7 at%, a high coercive force cannot be obtained. On the other hand, when Cr exceeds 12 at%, Br decreases and the output decreases. The coercive force and noise depend on the Ni concentration, and are contained at 18 at% to 28 at% in order to obtain a medium with high coercive force and low noise. 18 at
If it is less than%, a high coercive force cannot be obtained, and noise is large. Further, the coercive force is also reduced at 28 at% or more. Further, in the above magnetic recording medium, the average crystal grain size of the magnetic film alloy is preferably 200 angstroms to 350 angstroms. If the average crystal grain size of the magnetic film alloy is less than 200 angstroms, the coercive force tends to be small, and if it exceeds 350 angstroms, the noise of the magnetic film increases and the S / N decreases, which makes it unsuitable for high density recording. is there.

[0005]

The metal intermediate film made of Cr according to the present invention influences crystal growth when the underlying film and the magnetic film, which are sequentially stacked on the Cr intermediate film, are formed, the coercive force of the magnetic film is increased, and noise is generated. Get smaller. In addition, the composition of the magnetic film is set to 7
Cr of at% or more and 12 at% or less, 18 at% or more of 28
A magnetic recording medium with high coercive force and small noise can be obtained by using at% or less of Ni, the balance Co, and inevitable impurities.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic recording medium according to a preferred embodiment of the present invention will be described below with reference to the accompanying drawings. FIG.
FIG. 3 is a cross-sectional view of a magnetic recording medium that is an embodiment of the present invention. In the figure, 11 is a glass substrate such as chemically strengthened glass or crystallized glass, 12 is a metal intermediate film made of Cr having a thickness of 50 angstroms or more and 500 angstroms or less formed on the substrate, 13 is a base film such as a Cr film, 14 is a magnetic film made of CoNiCr, 15 is C,
A protective film 16 made of SiO2, ZrO2 or the like is a lubricating film. FIG. 2 is a partial sectional view of a magnetic recording medium of a comparative example.
1 is a glass substrate such as chemically strengthened glass or crystallized glass, 2
2 is a base film such as a Cr film, 23 is a magnetic film made of CoNiCr, 24 is a protective film made of C, SiO ₂ , ZrO _2, etc.
Reference numeral 25 is a lubricating film.

Example 1 Outer diameter 65 mm, inner diameter 20 m
After cleaning a glass substrate having a thickness of m and a thickness of 0.635 mm, it was evacuated to 1 × 10 ⁻⁶ Torr or less using a DC magnetron sputtering device, and the glass substrate was heated at 300 ° C. for 10 minutes, and then Ar gas was introduced to discharge it. Gas pressure of 10mT
The film thickness of the Cr intermediate film is 30 angstroms, 50 angstroms, 100 angstroms, 300 angstroms, 500 angstroms, 700 angstroms, and 1000 angstroms. Was changed to form a film on the glass substrate.
Next, the substrates on which the Cr intermediate films were formed were each evacuated to 1 × 10 ⁻⁶ Torr or less using a DC magnetron sputtering device, the substrates were heated at 300 ° C. for 10 minutes, Ar gas was introduced, and the gas pressure during discharge was set. Is held at 10 mTorr,
Cr underlayer of 500 Å, Co67Ni2
2Cr11 magnetic film 500 angstrom, protective film 2
A film of 50 Å was continuously formed.

(Comparative Example 1) A glass substrate having no intermediate film formed thereon was subjected to 1 × 1 using a DC magnetron sputtering apparatus.
After evacuating to below 0 ^-6 Torr, the substrate is heated at 300 ° C for 10
After heating for a minute, Ar gas was introduced to adjust the gas pressure during discharge to 10
While holding at mTorr, a Cr underlayer of 1000 Å, a Co67Ni22Cr11 magnetic layer of 500 Å, and a C protective layer of 250 Å were successively formed. With respect to the magnetic recording media manufactured in Example 1 and Comparative Example 1 described above, it was examined how the film thickness of the Cr intermediate film affects coercive force and disk noise. Cr
The relationship between the intermediate film thickness, the coercive force, and the disk noise is shown in FIG. As can be seen from FIG. 3, the coercive force increases as the Cr intermediate film thickness increases, and a coercive force of 1600 Oe or more can be obtained by using a Cr intermediate film of 50 Å or more and 500 Å or more. The coercive force is saturated at. It can be seen that the disk noise decreases once the Cr intermediate film is used, but the disk noise increases when the thickness of the Cr intermediate film exceeds 500 angstroms. From the above, by setting the thickness of the Cr intermediate film to be 50 angstroms or more and 500 angstroms or less, a magnetic recording medium suitable for high density recording can be obtained.

(Comparative Example 2) The metal film used as the intermediate film is T
A magnetic recording medium was manufactured in the same manner as in Example 1 except that i, Mo, and W were used, and Comparative Example 2 was obtained. The result of measuring the coercive force of the manufactured magnetic recording medium is shown in FIG. 4 together with the result of Example 1. Although the Ti intermediate film has an effect of increasing the coercive force, the effect is smaller than that of the Cr intermediate film. Also,
With Mo and W, the effect of improving the coercive force was hardly seen. Therefore, it was found that the Cr film is the best as the intermediate film.

(Example 2) In the magnetic recording medium manufactured in Example 1, the magnetic recording medium having a Cr intermediate film thickness of 300 angstroms and the magnetic film of the magnetic recording medium having no Cr intermediate film prepared in Comparative Example 1 were used. A transmission electron microscope image is shown in FIG. The average crystal grain size of the magnetic film of the magnetic recording medium not using the intermediate film is 380 angstroms, and the average crystal grain size of the magnetic film of the magnetic recording medium using the Cr intermediate film of 300 angstroms is 300 angstroms. Therefore, it can be seen that the average crystal grain size is small. In addition, the crystal grains of the magnetic film of the magnetic recording medium using the intermediate film have individual crystal grains clearer than those without the intermediate film, and there are few defects in the crystal grains, resulting in good crystal growth. You can see that It is considered that these differences are the cause of reducing the disk noise described in the first embodiment. Further, the magnetic films of the magnetic recording media having Cr intermediate film thicknesses of 500 Å, 700 Å and 1000 Å were also observed with a transmission electron microscope, and the average crystal grain size was determined and shown in Table 1. By using a Cr intermediate film of 50 angstroms or more and 500 angstroms or less, the average crystal grain size is reduced from 300 angstroms to 350 angstroms as compared with the case where the Cr intermediate film is not used, and when the Cr intermediate film thickness is further increased, the average crystal size gradually increases. There is a tendency for the grain size to increase, and when the Cr intermediate film thickness is 700 Å, the average crystal grain size is 380 Å, and when the Cr intermediate film thickness is 1000 Å, the average crystal grain size is 40 Å.
It became 0 angstrom. When combined with the measurement result of the disk noise shown in FIG. 3, the change of the disk noise almost coincides with the change of the average crystal grain size of the magnetic film, and the noise increases when the film thickness of the Cr intermediate film is larger than 500 Å, Not suitable for high density recording. From the above, C
When the thickness of the r intermediate film is 50 angstroms or more and 500 angstroms or less, a magnetic recording medium suitable for high density recording can be obtained.

Table 1 Intermediate film thickness (angstrom) Average crystal grain size (angstrom) 0 380 30 370 50 50 300 100 100 330 300 300 300 500 350 350 700 380 1000 400

(Example 3) In order to investigate the influence of the composition of the CoNiCr magnetic film on the magnetic characteristics and S / N characteristics, Co
Various magnetic recording media having different NiCr magnetic film compositions were used as C
r intermediate film is 500, Angstrom Cr base film thickness is 1
It was manufactured by the same method as in Example 1 except that the thickness was set to 000 angstrom. Composition, coercive force, residual magnetic flux density (Br) of the manufactured magnetic recording medium, S at linear recording density of 48 kFCI
The measurement results of / N are shown in Table 2.

[Table 2] CoNiCr composition and coercive force measurement results Sample No. Composition (at%) Hc (Oe) Br (kG) S / N (dB) 1 CoNi22Cr5 (Comparative example) 1430 11.0 29 2 CoNi22Cr6 (Comparative example) 1540 10.3 28 3 CoNi28Cr6 (Comparative example) 1500 9.8 28 4 CoNi20Cr7 (Invention) 1630 9.3 30 5 CoNi28Cr7 (Invention) 1700 9.2 31 6 CoNi30Cr7 (Comparative example) 1630 9.2 29 7 CoNi22Cr8 (Invention) 1640 8.5 32 8 CoNi25Cr8 (Invention) 1740 7.9 33 9 CoNi23Cr9 (Invention) 1710 7.0 33 10 CoNi17Cr10 (Comparative Example) 1790 6.6 28 11 CoNi18Cr10 (Invention) 1810 6.5 31 12 CoNi20Cr10 (Invention) 1790 6.7 33 13 CoNi22Cr10 (Invention) 1800 6.0 33 14 CoNi24Cr10 (invention) 1760 6.0 32 15 CoNi26Cr10 (invention) 1840 6.0 31 16 CoNi22Cr11 (invention) 1920 5.8 32 17 CoNi18Cr12 (invention) 1810 5.9 33 18 CoNi22Cr13 (comparative example) 1980 5.0 30 Sample 1 Sample 3 cannot obtain a coercive force of 1600 Oe because the Cr concentration is low. It can be seen that a coercive force of 1600 Oe or more is obtained with a composition having a Cr concentration of 7 at% or more, and the coercive force increases as the Cr concentration increases. On the other hand, the residual magnetic flux density Br decreases as the Cr concentration increases, and when the Cr concentration is 13 at%, the residual magnetic flux density is 5 kG.
And the reproduction output becomes small. Samples 6 and 10 had large coercive force and residual magnetic flux density, but the S / N was low and a magnetic recording medium suitable for high density recording could not be obtained. Looking at the change in S / N from Sample 10 with the Cr concentration fixed at 10 at% to Sample 15, the Ni concentration was 18a.
If it is less than t%, the S / N ratio drops sharply and the Ni concentration becomes 20%.
The S / N becomes maximum at at% to 22 at%, and N
It can be seen that the S / N decreases as the i concentration increases. From the above, the composition of the CoNiCr magnetic film is 7
Cr of at% or more and 12 at% or less, 18 at% or more of 28
It can be seen that a Ni content of at% or less can provide a magnetic recording medium suitable for high density recording. (Example 4) A magnetic recording medium was prepared in which CoNi20Cr10 was used as the magnetic film, the thickness of the Cr intermediate film was 500 angstroms, the thickness of the magnetic film was 500 angstroms, and the thickness of the Cr underlayer was changed. Coercive force,
The results of examining the S / N and average crystal grain size are shown in Table 3.

Table 3 Cr Underlayer film thickness (A) Coercive force (Oe) S / N Average crystal grain size (A) 0 450 Unmeasurable 150 100 100 800 20 180 180 300 1400 28 280 500 1500 1500 29 300 700 700 1700 30 300 300 1000 1800 32 290 1500 1850 31 340 2000 2000 1900 27 360 Table 2 shows that the Cr underlayer has a thickness of 0 angstrom or 1
In the case of 00 angstrom, the average crystal grain size is smaller than 200 angstrom and the coercive force is 450 Oe, respectively.
It turns out that it is as small as 800 Oe. Cr underlayer thickness of 30
When the thickness is 0 Å or more, the average crystal grain size becomes about 300 Å and the coercive force is 1400 Oe.
As described above, the coercive force becomes almost constant when the Cr underlayer film thickness is 1000 Å or more. Cr
It can be seen that when the underlayer film thickness is further increased to 2000 angstroms, the average crystal grain size is increased to 360 angstroms and the S / N is lowered.

[0012]

The above magnetic recording medium is provided with a Cr intermediate film, the magnetic film is CoNiCr, and the composition thereof is 7 at% to 12 at% Cr, 18 at% to 28 at% Ni, the balance Co and inevitable impurities. As a result, the coercive force can be increased. Further, by setting the Cr intermediate film 50 angstroms or more to 500 angstroms or less, the coercive force can be increased, the crystal growth of the base film and the magnetic film can be controlled, and noise can be reduced. Further, by setting the average crystal grain size of the magnetic film to be 200 angstroms or more and 350 angstroms or less, coercive force can be improved and noise can be reduced. By setting the coercive force of the magnetic film produced under the above conditions to 1600 Oe, a magnetic recording medium suitable for high density recording can be obtained.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a magnetic recording medium according to an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view of a magnetic recording medium of a comparative example.

FIG. 3 is a diagram showing a relationship between a film thickness of a Cr intermediate film, a coercive force, and noise.

FIG. 4 is a diagram showing a relationship between a film thickness and a coercive force of a Cr intermediate film (present invention), a Ti intermediate film (comparative example), a W intermediate film (comparative example), and a Mo intermediate film (comparative example).

FIG. 5 is an electron micrograph of a metal structure of a magnetic film with a Cr intermediate film (present invention) and without a Cr intermediate film (comparative example).

[Explanation of symbols]

11 glass substrate, 12 Cr intermediate film, 13 Cr underlayer film, 14 CoNiCr magnetic film, 15 protective film, 16
Lubricating film, 21 glass substrate, 22 underlayer film, 23 magnetic film, 24 protective film, 25 lubricating film.

Claims (5)

[Claims] 1. A magnetic recording medium comprising a glass substrate on which a base film of Cr or the like, a magnetic film and a protective film are sequentially laminated.
A magnetic recording medium comprising a metal intermediate film made of Cr for controlling a fine structure of the underlayer between the glass substrate and the underlayer. 2. The magnetic recording medium according to claim 1, wherein the magnetic film is composed of 7 at% or more and 12 at% or less Cr, 18 at% or more and 28 at% or less Ni, the balance Co and inevitable impurities. 3. The magnetic recording medium according to claim 1, wherein the film thickness of the metal intermediate film is 50 angstroms to 500 angstroms. 4. The magnetic recording medium according to claim 1, wherein the average crystal grain size of the magnetic film is 200 angstroms to 350 angstroms or less. 5. The magnetic recording medium according to claim 1, which has a coercive force of 1600 Oe or more.