JPH09138936A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a magnetic recording medium which has high coercive force and a proper squareness ratio of antimagnetization and is suitable for high-density recording even when the film thickness of a magnetic film is small, namely, the product of the residual magnetization and the film thickness of the magnetic film is small. SOLUTION: This medium has a base film 12 of a material essentially comprising vanadium formed on a substrate 11 and a magnetic film 13 comprising a CoPtO alloy formed on the base film 12. The medium has a first base film 22 having a crystal structure which forms a body centered cubic lattice formed on a substrate 21, a second base film 23 comprising an amorphous material formed on the first base film 22, and a magnetic film 24 comprising a CoPtO alloy formed on the second base film 23.

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 for a magnetic recording device such as a hard disk device which is an external storage device of a computer.

[0002]

2. Description of the Related Art A magnetic recording device is used as a high-density recording device because it has advantages of small size, large capacity, high speed access, and low cost. In recent years, there has been a demand for higher density recording in magnetic recording devices, and magnetic recording media for high density recording have been studied to meet this demand.

In order to achieve high density recording, the coercive force (Hc) of the magnetic film should be increased, the thickness of the magnetic film should be reduced, and the anisotropy of the grains forming the magnetic film should be uniform. Examples include reducing the dispersion of the magnetic field.

As a conventional magnetic recording medium satisfying high Hc, there is a magnetic recording medium in which a CoPt alloy film is directly formed as a magnetic film on a substrate. However, in these conventional magnetic recording media, when the film thickness of the magnetic film is reduced, the coercive force gradually increases and becomes suitable for high density recording. Fall to. Therefore, in the conventional magnetic recording medium, there is a problem that the improvement of the recording density cannot be achieved even if the magnetic film is thinned.

In the magnetic recording medium, the coercive force squareness ratio S ^* in the in-plane direction of the magnetic film affects the signal quality. It is suitable that S ^* is about 0.4 to 0.8, but a conventional magnetic recording medium does not show a value in this range when it is made thin.

Therefore, a first object of the present invention is to reduce the residual magnetization amount (Mr) of the magnetic film even if the magnetic film is thin.
It is an object of the present invention to provide a magnetic recording medium exhibiting a high coercive force even if the product of the magnetic film thickness (t) and the coercive force squareness ratio is suitable for high density recording.

On the other hand, in a thin film magnetic recording medium, it is effective for high density recording to promote magnetic separation between magnetic particles in the magnetic film in order to increase the coercive force and noise of the medium. ΔM is an index indicating the degree of magnetic separation between the magnetic particles. ΔM is a parameter that can evaluate the magnetic separation degree of the magnetic recording medium regardless of the recording capability of the magnetic head. The smaller ΔM is, the higher coercive force and low noise the magnetic recording medium has.

In the current magnetic recording apparatus, a magnetic film having Hc of about 2000 Oe is used as a magnetic recording medium. At present, the recording capacity of the magnetic head limits the Hc of the magnetic recording medium, but with the improvement of the recording capacity of the magnetic head in the future, it is desired to increase the Hc of the magnetic recording medium.

However, in the conventional magnetic recording medium,
There is a problem that ΔM does not become sufficiently small. Therefore, the magnetic recording medium in which the CoPtO alloy film is directly formed on the substrate has a limit in coercive force, and there is a problem that high density recording cannot be achieved.

Therefore, a second object of the present invention is to provide a magnetic recording medium suitable for high density recording in which magnetic particles are magnetically separated in a magnetic film and which exhibits a high coercive force.

[0011]

Means for Solving the Problems A first invention of the present invention is:
Provided is a magnetic recording medium comprising a base film formed on a substrate and a magnetic film formed on the base film and made of a CoPtO-based alloy.

The first invention of the present invention is that the base film formed on the substrate and the base film are formed by C
a magnetic film composed of an oPtO-based alloy, and the magnetization amount v · I _{sb of the} magnetic film is 0 <v · I _sb ≦ 0.3 × 10.
A magnetic recording medium satisfying ^-14 emu is provided.

A first invention of the present invention is that a base film formed on a substrate and the base film is formed by C
a magnetic film made of an oPtO-based alloy, and a value Hc / (Mr · Hc) of a coercive force Hc with respect to a product Mr · t of the residual magnetization in the in-plane direction of the magnetic film and the film thickness of the magnetic film.
t) (Oe / (memu / cm ² )) is at least 60
A magnetic recording medium of No. 00 is provided.

[0014] Here, the product Mr · t and the ratio of the magnetization v · I _sb of the magnetic film (Mr · t / v · I sb between the residual magnetization in the plane direction of the magnetic film and the thickness of the magnetic layer ) Is 3.5 ×
It is preferably 10 ¹¹ pieces / cm ² or more.

In the first aspect of the present invention, a base film formed on a substrate and the base film is formed, and C
a magnetic film composed of an oPtO-based alloy, the magnetic film having a thickness of 15 nm or less, and the coercive force square S ^* in the in-plane direction of the magnetic film being 0.4 to 0.82. A recording medium is provided. Here, the base film is preferably made of a material whose main component is vanadium.

In the first aspect of the invention, it is preferable that the base film and the CoPtO-based alloy are lattice-matched by the base film. In the first invention, it is preferable that the CoPtO-based alloy forming the magnetic film contains at least 10 atomic% oxygen, and the magnetic film has a crystal phase and an amorphous phase containing more oxygen than the crystal phase. Further, it is preferable that the magnetic film has magnetic anisotropy in the in-plane direction.

According to a second aspect of the present invention, there is provided a first underlayer film formed on a substrate, the first underlayer film being made of a crystal having a crystal structure forming a body-centered cubic lattice, and the first underlayer film. A second undercoating film formed of an amorphous material, and CoPtO formed over the second undercoating film.
A magnetic recording medium comprising a magnetic film made of a system alloy.

In the second invention, it is preferable that the first underlayer film is formed in a plurality of islands on the substrate in order to magnetically separate the magnetic film. Further, the material forming the first underlayer preferably contains at least one element selected from the group consisting of niobium, vanadium and chromium, and the material forming the second underlayer is carbon, boron,
It is preferable to contain at least one selected from the group consisting of boron nitride and silicon dioxide.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. The magnetic recording medium according to the first aspect of the present invention, as shown in FIG.
The magnetic film 13 is formed with the intermediate layer 2 interposed therebetween.

In the first invention, the magnetization amount v of the magnetic film is
-I _sb is set to satisfy 0 <v · I _sb ≦ 0.3 × 10 ⁻¹⁴ emu, preferably 0 <v · I _sb ≦ 0.2 × 10 ⁻¹⁴ emu. This is to improve the S / N (signal noise) ratio.

V · I _sb (emu) is a state in which a vibrating sample magnetometer (VSM) is used to apply a magnetic field that saturates the magnetic film to the magnetic film, and then a magnetic field in the opposite direction to saturation is applied. The amount of magnetization is monitored by, and the relationship between the magnetic field (coercive force Hc) and the time (sec) until the magnetization becomes 0 is obtained and calculated by the following formula I.

V · I _sb = {kT / (ΔHc / ΔIn (t))} Formula I (k: Boltzmann constant, T: absolute temperature) v · I _sb represents the magnetic moment of one particle. Since this is an index, if this value is small, it means that the particles are finely divided. The present inventors have found that CoP is formed on a substrate through an underlying film.
By forming a magnetic film composed of a tO alloy,
The fact that the material forming the magnetic film is made into fine particles is
It was first discovered by examining _sb . When the material forming the magnetic film is made into fine particles, the S / N ratio becomes large according to the following formula II.

ΔS / N = 10 · log (n ₁ / n ₂ ) ... Formula II (n ₁ , n ₂ : the number of particles) In the first invention, the residual magnetization amount in the in-plane direction of the magnetic film. The value Hc / (Mr · t) of the coercive force Hc with respect to the product Mr · t of the magnetic film and the magnetic film thickness is at least 60.
It should be 00. Hc / (Mr · t) is set to at least 6000 for the purpose of high recording resolution and low noise.

Considering the relationship between Mr · t and v · I _sb , Mr · t / v · I _sb is 3.5 × 10 ¹¹ pieces / cm ^2.
It is preferable that it is above. This is because the number of magnetic particles per bit is taken into consideration. Thus Mr · t /
The S / N ratio can be increased by defining v · I _sb .

Further, in the first invention, the film thickness of the magnetic film is 15 nm or less, and the coercive force square S ^* in the in-plane direction of the magnetic film is 0.4 to 0.82. The thickness of the magnetic film is set to 15 nm or less for high recording resolution. Moreover, the coercive force square S ^* in the in-plane direction of the magnetic film is set to 0.4 to 0.82.
This is for higher output and lower noise.

In the first aspect of the present invention, the fact that the material constituting the substrate is lattice-matched with the CoPtO-based alloy by the underlayer means that the average atomic radius of the substrate material and the average atomic radius of the CoPtO-based alloy are about 3%. It should be close within
They do not have to match.

In the first aspect of the present invention, the material containing vanadium as a main component of the underlayer is V, V-Nb alloy,
It means a V-Ta alloy or a V-Nb-Ta alloy. In the first invention, as a base film, a V film, a V-Nb alloy film,
By using the V-Ta alloy film, it is possible to suppress a decrease in coercive force of the CoPtO magnetic film. This is because the underlying film reduces stacking faults in the crystal phase of the CoPtO magnetic film of the ultra-thin film formed thereon, lowers the magnetic anisotropy of the CoPtO-based alloy particles, and increases the magnetic anisotropy. Is prevented from being dispersed.

In this case, the coercive force of the magnetic film and the squareness ratio S ^* can be controlled by changing the solid solution amount of Nb and Ta dissolved in V, and the coercive force with respect to the recording ability of the magnetic head. Can be optimized and the signal quality can be improved.

Further, by imparting orientation or shape anisotropy to the underlayer film, it is possible to improve the squareness ratio of magnetic characteristics in a magnetic film provided with magnetic anisotropy having an easy axis in the circumferential direction. Therefore, the output and recording density can be further increased. Further, since the magnetic film has magnetic anisotropy in the in-plane direction, the magnetic aftereffect can be reduced.

A protective film made of carbon or the like or a lubricant layer made of perfluoropolyether or the like may be provided on the surface of the magnetic film. The magnetic recording medium of the second invention of the present invention comprises:
As shown in FIG. 5, a magnetic film 24 is formed on a substrate 21 with a first underlayer film 22 and a second underlayer film 23 interposed therebetween. A protective film 25 is formed on the magnetic film 24 as needed.

In the second invention, in the magnetic film,
Co having a close-packed hexagonal structure on the crystalline region of the second underlayer
PtO grows, and C is formed on the amorphous region of the second base film.
There is an amorphous region containing a large amount of oxygen in oPtO. Therefore, the separation of the magnetic particles in the magnetic film is promoted,
High Hc of over 4000 Oe and ΔM of 0.2 or less
Is achieved. Therefore, it is possible to provide a magnetic recording medium having a high linear resolution, low noise, and a high S / N ratio.

In the first and second inventions, a glass substrate, a silicon substrate, a carbon substrate or the like can be used as the substrate. In addition, CoPt forming the magnetic film
The O-based alloy means an alloy containing at least 10 atomic% of oxygen in a CoPt alloy, and CoPtO contains Cr and Z.
It also includes those containing additional elements such as r and Ta. With this CoPtO-based alloy having a crystal phase and an amorphous phase containing more oxygen than the crystal phase, the signal quality of the magnetic recording medium is improved and the medium noise can be reduced. Further, since this structure has a large crystal magnetic anisotropy in nature, it is suitable as a material for future magnetic recording media for high density recording.

Embodiments of the present invention will be specifically described below with reference to the drawings. (Example 1) A V film having a thickness of 360 nm was formed on a glass substrate by sputtering. For the sputtering, a V target having an outer diameter of 5 inches was used, the distance between the target and the substrate was 170 mm, the sputtering pressure was 2 Pa, and the input power was 2.5 kW.
Went below.

Then, a CoPtCrO film having a thickness of 5 to 20 nm and containing 25 atomic% of oxygen was formed on the V film. CoP
The tCrO film is formed of Co-20 atomic% with an outer diameter of 5 inches.
A Pt-3 atom% Cr target was used, the target-substrate distance was 170 mm, the Ar sputtering pressure containing oxygen was 12 Pa, and the applied power was 120 W. Note that C
Regarding the oPtCrO film, various thicknesses were formed by controlling the time during sputtering.
In this way, CoPt is formed on the glass substrate through the V film.
Various magnetic recording media having different thicknesses of magnetic films, each having a CrO film formed, were manufactured.

A 21 nm thick Nb film was formed on the glass substrate by sputtering. The sputtering was performed using a Nb target having an outer diameter of 5 inches, a target-substrate distance of 150 mm, a sputtering pressure of 0.6 Pa, and an input power of 2 kW. Furthermore, a carbon film having a thickness of 9 nm was formed on the Nb film by sputtering. The sputtering was performed using a carbon target having an outer diameter of 5 inches, a target-substrate distance of 150 mm, a sputtering pressure of 2 Pa, and an input power of 1 kW. Then N
Co having a thickness of 5 to 20 nm containing 25 atomic% of oxygen on the b film
A PtCrO film was formed in the same manner as above. In this way, various magnetic recording media having different thicknesses of the magnetic film, in which the CoPtCrO film was formed on the glass substrate via the carbon film and the Nb film, were produced.

As a conventional example, various magnetic recording media in which the CoPtCrO film was formed directly on a glass substrate by sputtering and the magnetic film thickness was different were prepared. The CoPtCrO film was formed in the same manner as above.

The residual magnetization of each of these magnetic recording media was measured using a vibrating sample magnetometer (VSM),
The residual magnetization amount and the magnetic film thickness Mr · t were calculated. Also,
V · I _sb (magnetization amount of magnetic particles) of the magnetic film was calculated based on the measurement result by the vibrating sample magnetometer (VSM). FIG. 2 shows the relationship between Mr · t and v · I _sb calculated in this way.

As can be seen from FIG. 2, the magnetic recording medium of the present invention (CoPtCrO / V / Sub, CoPtCrO /
C / Nb / Sub) has v · I _sb of 0.2 × 10 ⁻¹⁴ em
It was less than u. On the other hand, conventional magnetic recording media (CoPt
CrO / Sub) has v · I _sb of 0.3 × 10 ⁻¹⁴ emu
Above, especially when Mr · t is 0.6 memu / cm ² or less, it becomes large near 1.0 × 10 ⁻¹⁴ emu.

In the magnetic recording medium of the present invention, Mr.
The value of t / v · I _sb was 5.5 × 10 ¹¹ pieces / cm ² , whereas in the conventional magnetic recording medium, Mr · t / v · I _sb.
Is 3.0 × 10 ¹¹ pieces / cm ² , and Mr.
When t is 0.6 memu / cm ² or less, the value of Mr · t / v · I _sb sharply decreases.

In the magnetic recording medium of the present invention, Mr.
S / N is 36d when t is less than 0.6 memu / cm ^2.
However, in the conventional magnetic recording medium, Mr.
S / N is 20d when t is less than 0.6 memu / cm ^2.
It was B or less. (Example 2) A V film having a thickness of 360 nm was formed on a glass substrate by sputtering in the same manner as in Example 1. Then, a CoPtO film containing 25 atomic% of oxygen is formed on the V film by C
It was formed in the same manner as in Example 1 except that a Co-24 atom% Pt target was used instead of the o-20 atom% Pt-3 atom% Cr target. Regarding the CoPtO film, various film thicknesses were formed by controlling the time during sputtering. In this way,
Various magnetic recording media in which the CoPtO film was formed on the glass substrate via the V film and the magnetic films had different thicknesses were manufactured.

As a conventional example, various magnetic recording media in which the CoPtO film was directly formed on a glass substrate by sputtering and the thickness of the magnetic film was different were prepared. Note that C
The oPtO film was formed in the same manner as above.

The magnetic characteristics of these magnetic recording media were measured using a vibrating sample magnetometer (VSM), and the residual magnetization, coercive force and coercive force squareness ratio were determined. By using the obtained results of the residual magnetization amount and the coercive force, the residual magnetization amount, the magnetic film thickness Mr.t, the coercive force Hc, and the coercive force squareness ratio S are used.
The relationship with ^* is shown in FIG.

As can be seen from FIG. 3, in the magnetic recording medium of the present invention using the V film as the underlayer, when the film thickness t of the magnetic film is 15 nm, the residual magnetization amount and the film thickness of the magnetic film are The product Mr · t was 0.48 memu / cm ² , and the coercive force Hc was 2750 Oe. Also, t is 9.8 nm
At that time, Mr · t was 0.35 memu / cm ² and Hc was 2600 Oe. Further, when t is 6 nm, Mr · t is 0.15 memu / cm ² ,
Hc was 1900 Oe.

When the magnetic film of the magnetic recording medium of the present invention was analyzed by an analytical electron microscope, the structure thereof consisted of a crystalline phase and an amorphous phase, and a large amount of oxygen was segregated in the amorphous phase. confirmed. Further, the coercive force squareness ratio S ^* was a good value in all 0.4 to 0.6 or less.

On the other hand, in the conventional magnetic recording medium in which the magnetic film is directly formed on the glass substrate, Mr.t is 0.9 memu / cm ² and Hc is 2100 Oe when t is 17 nm. There was no level. However, when t is 13.8 nm, Mr · t is 0.6.
² memu / cm ² , Hc is 1760 Oe, and t is 10 nm, Mr · t is 0.56 mem
u / cm ² , Hc was 310 Oe, and it was found that the coercive force sharply decreased when the magnetic film became thin. (Example 3) A V film having a thickness of 120 nm was formed on a glass substrate by sputtering. For sputtering, a V target having an outer diameter of 5 inches was used, the distance between the target and the substrate was 170 mm, the sputtering pressure was 0.65 Pa, and the input power was 2.
It was conducted under 5 kW.

Then, a CoPtCrO film was formed on the V film. The CoPtCrO film is formed with Co having an outer diameter of 5 inches.
-20 atom% Pt-3 atom% Cr target was used, the target-substrate distance was set to 170 mm, and oxygen containing A was used.
The r sputtering pressure was set to 12 Pa, and the applied power was 200 W. Regarding the CoPtCrO film, various film thicknesses were formed by controlling the time during sputtering. In this manner, various magnetic recording media having different thicknesses of the magnetic film, in which the CoPtCrO film was formed on the glass substrate via the V film, were manufactured.

As a conventional example, various magnetic recording media having different magnetic film thicknesses were produced by directly forming a CoPtCrO film on a glass substrate by sputtering. The CoPtCrO film was formed in the same manner as above.

The magnetic characteristics of these magnetic recording media were measured using a vibrating sample magnetometer (VSM), and the residual magnetization amount, coercive force, and coercive force squareness ratio were determined. By using the obtained results of the residual magnetization amount and the coercive force, the residual magnetization amount, the magnetic film thickness Mr.t, the coercive force Hc, and the coercive force squareness ratio S are used.
The relationship with ^* is shown in FIG.

As can be seen from FIG. 4, in the magnetic recording medium of the present invention using the V film as the underlayer, when the film thickness t of the magnetic film is 15 nm, the residual magnetization amount and the film thickness of the magnetic film are The product Mr · t was 0.48 memu / cm ² , and the coercive force Hc was 3200 Oe. Further, when t is 9 nm, Mr · t is 0.35 memu / cm ² , and H
c was 2800 Oe. Further, when t is 7 nm, Mr · t is 0.22 memu / cm ² , and Hc
Was 2350 Oe.

When the magnetic film of the magnetic recording medium of the present invention was analyzed by an analytical electron microscope, the structure thereof consisted of a crystalline phase and an amorphous phase, and a large amount of oxygen was segregated in the amorphous phase. confirmed. Furthermore, the coercive force squareness ratio S ^* was a good value in all 0.4 to 0.65.

On the other hand, in the conventional magnetic recording medium in which the magnetic film is directly formed on the glass substrate, when t is 24 nm, Mr · t is 0.9 memu / cm ² and Hc is 2100 Oe. There was no level. However, when t is 8 nm, Mr · t is 0.58 me.
mu / cm ² , Hc is 1700 Oe, and t is 6 nm, Mr · t is 0.55 memu / cm ^2.
It was found that Hc was 300 Oe, and the coercive force drastically decreased when the magnetic film became thin. In addition, the coercive force squareness ratio S ^* was extremely large, which deviated from the practical level optimum range of 0.4 to 0.82.

When a Cr film is used as the base film,
When Mr · t was 0.5 or less, the coercive force was 1100 Oe and the squareness ratio was 0.3. Also, C containing no oxygen
In the film structure of oPt / V, the film thickness of Mr · t is small.
Was less than 0.5, the noise was large. (Example 4) A 50-nm-thick V-Nb film was formed on a glass substrate by sputtering. Sputtering is
Using a V target and an Nb target having an outer diameter of 5 inches, the target-substrate distance was 120 mm, and the sputtering pressure was 0.3 Pa. Regarding the V-Nb film,
By controlling the input power during sputtering,
Various compositions were formed.

Next, a 12 nm thick C film was formed on the V-Nb film.
An oPtCrO film was formed. The CoPtCrO film is formed by forming Co-26 atomic% Pt-3 atomic% C with an outer diameter of 5 inches.
The target-substrate distance is set to 200 by using the r target.
mm, the Ar sputtering pressure containing oxygen is 10 Pa,
The input power was 2.5 kW. In this way, various magnetic recording media having different compositions of the underlying film material, in which the CoPtCrO film was formed on the glass substrate via the V-Nb film, were manufactured.

As a conventional example, a magnetic recording medium was produced by directly forming a CoPtCrO film on a glass substrate by sputtering. The CoPtCrO film was formed in the same manner as above.

The magnetic characteristics of these magnetic recording media were measured using a vibrating sample magnetometer (VSM), and the residual magnetization, coercive force and coercive force squareness ratio were determined. as a result,
A magnetic recording medium using a base film of V-10 atom% Nb is
The maximum Hc value was 2800 Oe, which was higher than that when the V film was used as a base film (2200 Oe). Also,
Mr.t was 0.36 memu / cm ² .

The magnetic recording medium using the V-Nb film containing Nb in an amount of 10 atomic% or more as the base film had a low coercive force. Further, the coercive force squareness ratio S ^* increased to 0.65 to 0.70 up to the Nb content of 10 atom%, and decreased when the Nb content further increased.

On the other hand, in the conventional magnetic recording medium in which the magnetic film is directly formed on the glass substrate, the coercive force is 500 Oe.
Was low. In Example 4, the substrate was rotated to form a V-Nb film while heating with an infrared lamp from the substrate surface side so as to have a temperature gradient from the inner circumference to the outer circumference of the substrate, and the CoPtCrO film was formed thereon. By doing so, magnetic anisotropy having an easy axis in the circumferential direction was imparted to the magnetic film. At this time, the coercive force squareness ratio S ^* increased to 0.7 to 0.82 in the optimum range. (Example 5) First by sputtering on a glass substrate
A 21-nm-thick Nb film was formed as the underlayer film. For sputtering, an Nb target with an outer diameter of 5 inches was used.
Target-substrate distance 170mm, sputter pressure 2P
a, Input power was 2.5 kW. Nb film thickness 21
nm is a value at which the crystal orientation is sufficient.

Next, a carbon film having a thickness of 10 nm, which is a second base film, was formed on the Nb film by sputtering. Sputtering was performed using a C target having an outer diameter of 5 inches, a target-substrate distance of 170 mm, a sputtering pressure of 2 Pa, and an input power of 600 W. Regarding the carbon film, various thicknesses were formed by controlling the time during sputtering.

Then, a 20 nm thick CoPtO film, which is a magnetic film, was formed on the carbon film by sputtering. For sputtering, a Co-24 atom% -Pt target with an outer diameter of 5 inches was used, and the target-substrate distance was 1
70 mm, Ar sputtering pressure containing oxygen was 8 Pa, and input power was 400 W.

Finally, a carbon film having a thickness of 10 nm was formed as a protective film on the CoPtO film by sputtering. Sputtering was performed using a C target having an outer diameter of 5 inches, a target-substrate distance of 170 mm, an Ar sputtering pressure of 2 Pa, and an input power of 600 W.

The coercive force of various magnetic recording media thus produced having different second underlayer film thicknesses was measured using a vibrating sample magnetometer (VSM). The results are shown in FIG. 6 and Table 1 below.

[0062]

[Table 1]

As is clear from FIG. 6 and Table 1, the magnetic recording media (Samples 2 to 5) of the present invention having the carbon film as the second underlayer have a very high coercive force Hc, ΔM was also small. On the other hand, the magnetic recording medium (Sample 1) having no carbon film has a coercive force Hc.
Was very low and ΔM was large.

It is considered that the carbon film also has an effect of preventing the diffusion of Nb into the CoPtO film, and this effect is also considered to have contributed to the high Hc. (Example 6) First by sputtering on a glass substrate
A 21-nm-thick Nb film was formed as the underlayer film. For sputtering, an Nb target with an outer diameter of 5 inches was used.
Target-substrate distance 170 mm, sputtering pressure 0.6
It was performed under Pa and input power of 2.5 kW. Nb film thickness 2
1 nm is a value at which the crystal orientation is sufficient.

Then, a carbon film having a thickness of 13 nm, which is a second base film, was formed on the Nb film by sputtering. The sputtering was performed using a C target having an outer diameter of 5 inches, a target-substrate distance of 120 mm, a sputtering pressure of 2 Pa, and an input power of 600 W. Regarding the carbon film, various thicknesses were formed by controlling the time during sputtering.

Then, a CoPtO film having a thickness of 24.5 nm, which is a magnetic film, was formed on the carbon film by sputtering. Sputtering is Co-24 with an outer diameter of 5 inches
Using an atomic% Pt target, the target-substrate distance was 170 mm, the Ar sputtering pressure containing oxygen was 12 Pa, and the applied power was 120 W. Regarding the CoPtO film, by controlling the time during sputtering,
Various film thicknesses were formed.

Finally, a carbon film having a thickness of 8 nm was formed as a protective film on the CoPtO film by sputtering. For sputtering, a Co-24 atom% Pt target having an outer diameter of 5 inches was used, and the target-substrate distance was 17
0 mm, Ar sputtering pressure 2 Pa, input power 600 W.

The coercive force of various magnetic recording media thus produced having different magnetic film thicknesses was measured using a vibrating sample magnetometer (VSM). The results are shown in FIG. 7 and Table 2.

[0069]

[Table 2]

As is clear from FIG. 7 and Table 2, C
The magnetic recording media (Samples 3 and 4) having an oPtO film thickness of 14 nm or more had a very large coercive force. Also,
At this time, ΔM was small.

FIG. 8 shows a transmission electron microscope image of the surface of the CoPtO film formed on the Nb film. Further, FIG. 9 shows a transmission electron microscope image of the surface of the CoPtO film formed on the Nb film via the carbon film. As can be seen from FIGS. 8 and 9, in the structure shown in FIG. 9, the amorphous phase between magnetic particles is widened. Therefore, it is considered that the CoPtO film formed on the Nb film via the carbon film reduces the exchange interaction between the magnetic particles, which results in high Hc and ΔM
Seems to have become smaller.

In Examples 5 and 6, the Nb film is used as the first underlayer film and the carbon film is used as the second underlayer film. However, as the material of the first underlayer film, The same effect can be obtained by using a material containing at least one element selected from the group consisting of Nb, V, and Cr. As the material for the second underlayer, boron, boron nitride, and silicon dioxide are used. The same effect can be obtained by using a material containing at least one selected from the group consisting of

[0073]

As described above, the magnetic recording medium of the first invention of the present invention is composed of a base film formed on a substrate and a CoPtO-based alloy formed on the base film. Since the magnetic film is provided, even if the film thickness of the magnetic film is thin, that is, even if the product of the residual magnetization amount (Mr) of the magnetic film and the film thickness (t) of the magnetic film is small, a high coercive force is exhibited. It is suitable for density recording.

This makes it possible to reduce the width of the magnetic transition of the magnetic recording medium when recording with the magnetic head and increase the recording density. In addition, since the width of the magnetization transition is reduced, the amount of noise from the magnetization transition region is reduced, and the S / N ratio of the magnetic recording medium is improved. In addition, since the magnetic anisotropy is uniform in the magnetic film, the influence of thermal agitation is reduced.

The magnetic recording medium according to the second aspect of the present invention is formed on a substrate and has a first underlayer composed of crystals having a crystal structure forming a body-centered cubic lattice; A second underlayer film formed on the first underlayer film and made of an amorphous material; and a magnetic film formed on the second underlayer film and made of a CoPtO-based alloy. Therefore, the magnetic particles are magnetically separated in the magnetic film, which is suitable for high-density recording showing a high coercive force.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a magnetic recording medium according to a first invention of the present invention.

FIG. 2 is a characteristic diagram showing a magnetization amount of a magnetic film in the magnetic recording medium according to the first aspect of the present invention.

FIG. 3 is a characteristic diagram showing magnetic characteristics of the magnetic recording medium according to the first aspect of the present invention.

FIG. 4 is a characteristic diagram showing magnetic characteristics of the magnetic recording medium according to the first aspect of the present invention.

FIG. 5 is a sectional view showing a magnetic recording medium according to a second invention of the present invention.

FIG. 6 is a characteristic diagram showing the film thickness dependence of the coercive force of the second underlayer film in the magnetic recording medium according to the second invention of the present invention.

FIG. 7 is a characteristic diagram showing the dependence of coercive force on the thickness of a magnetic film in a magnetic recording medium according to a second aspect of the present invention.

FIG. 8 is a micrograph showing a conventional magnetic recording medium having only an Nb underlayer.

FIG. 9 is a micrograph showing a magnetic recording medium according to the second invention of the present invention in which a carbon underlayer is formed on an Nb underlayer.

[Explanation of symbols]

11, 21 ... Base, 12 ... Underlayer film, 13, 24 ... Magnetic film, 22 ... First underlayer film, 23 ... Second underlayer film, 25 ...
Protective film.

Claims (15)

[Claims] 1. A base film formed on a base body and made of a material containing vanadium as a main component, and a magnetic film formed on the base film and made of a CoPtO-based alloy. A magnetic recording medium characterized by: 2. The magnetic recording medium according to claim 1, wherein the material forming the substrate and the CoPtO-based alloy are lattice-matched by the base film. 3. A base film formed on a substrate, and a magnetic film formed on the base film and made of a CoPtO-based alloy, wherein the magnetization amount v · I _{sb of the} magnetic film is 0 <
A magnetic recording medium characterized by satisfying v · I _sb ≦ 0.3 × 10 ⁻¹⁴ emu. 4. The ratio (Mr · t / v · I _sb) of the product Mr · t of the residual magnetization amount in the in-plane direction of the magnetic film and the film thickness of the magnetic film and the magnetization amount v · I _sb of the magnetic film. ) Is 3.5 × 1
The magnetic recording medium according to claim 3, wherein the number is 0 ¹¹ pieces / cm ² or more. 5. The magnetic recording medium according to claim 3, wherein the base film is made of a material whose main component is vanadium. 6. A residual magnetization amount in the in-plane direction of the magnetic film, comprising: a base film formed on a substrate; and a magnetic film formed on the base film and made of a CoPtO-based alloy. A magnetic recording medium having a value Hc / (Mr · t) of coercive force Hc with respect to the product Mr · t of the magnetic film and the film thickness of the magnetic film is at least 6000. 7. The magnetic recording medium according to claim 6, wherein the base film is made of a material whose main component is vanadium. 8. A base film formed on a substrate, and a magnetic film formed on the base film and made of a CoPtO-based alloy, wherein the magnetic film has a thickness of 15 nm or less. A magnetic recording medium, wherein the coercive force square S ^* in the in-plane direction of the magnetic film is 0.4 to 0.82. 9. The magnetic recording medium according to claim 8, wherein the base film is made of a material whose main component is vanadium. 10. The CoPtO-based alloy forming the magnetic film contains at least 10 atomic% oxygen, and the magnetic film has a crystalline phase and an amorphous phase containing more oxygen than the crystalline phase. Magnetic recording medium. 11. The magnetic recording medium according to claim 1, wherein the magnetic film has magnetic anisotropy in an in-plane direction. 12. A first underlayer film formed on a substrate and made of a crystal having a crystal structure forming a body-centered cubic lattice; and a first underlayer film formed on the first underlayer film. A magnetic recording medium comprising: a second underlayer film made of a crystalline material; and a magnetic film formed on the second underlayer film and made of a CoPtO-based alloy. 13. The magnetic recording medium according to claim 12, wherein the first underlayer film is formed in a plurality of islands on the substrate. 14. The magnetic recording medium according to claim 12, wherein the material forming the first underlayer contains at least one element selected from the group consisting of niobium, vanadium, and chromium. 15. The magnetic recording medium according to claim 12, wherein the material forming the second underlayer contains at least one selected from the group consisting of carbon, boron, boron nitride, and silicon dioxide.