JPH11283229A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium with which a general purpose signal processing method can be applied as it is for an inside magnetic recording medium and noise characteristics are improved. SOLUTION: An in-plane magnetic film 3 with its axis of easy magnetization oriented in the inside direction in respect of a substrate and a vertical magnetic film 6 with the axis of easy magnetization oriented vertically to the substrate are formed on a substrate 1, wherein the inside magnetic film 3 is provided on the side of the substrate 1 rather than the vertical magnetic film 6, and its coercive force Hc is set at 1500 to 4000Oe, a residual magnetized film thickness product BrT is set at 20 to 100 Gμm, the coercive force Hc of the vertical magnetic film 6 is set at 1500 to 4000Oe and the film thickness is set at 100 to 1000 Å.

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, and more particularly to a magnetic recording medium having excellent noise characteristics.

[0002]

2. Description of the Related Art Most magnetic recording media currently on the market are in-plane magnetic recording media in which the axis of easy magnetization in a magnetic film is mainly oriented horizontally to a substrate. In such an in-plane magnetic recording medium, when the recording density is increased, the bit volume becomes too small, and the reproduction characteristics may be deteriorated due to a thermal fluctuation effect or the like. It is also known that when the recording density is increased, medium noise may increase due to an increase in the magnetization reversal transition region and the like. On the other hand, in a so-called perpendicular magnetic recording medium in which the easy axis of magnetization in the magnetic film is oriented perpendicular to the substrate, a steep magnetization transition is formed and the recording density increases even when the recording density is increased. As the demagnetizing field becomes smaller and more stable, noise can be reduced, and high recording density can be achieved even with a relatively large bit volume. However, a perpendicular magnetic recording medium is different from an in-plane magnetic recording medium in that the reproduced waveform is different from the in-plane magnetic recording medium, that is, the isolated waveform is not a single-peak type but includes a dipulse waveform. It is difficult to apply the used signal processing method as it is. For this reason, a perpendicular in-plane composite magnetic recording medium has been proposed which has two films, an in-plane magnetic film and a perpendicular magnetic film, and enables the use of the same signal processing method as that used for the in-plane magnetic recording medium. I have.

[0003]

In recent years, there has been a demand for a higher recording density of a magnetic recording medium, and accordingly, an improvement in noise characteristics has been demanded. However, the noise characteristics of conventional magnetic recording media have never been satisfactory, and there has been a demand for magnetic recording media having better noise characteristics. The present invention has been made in view of the above circumstances, and a signal processing method generally used when using a longitudinal magnetic recording medium can be applied as it is, and a magnetic recording medium having excellent noise characteristics. The purpose is to provide.

[0004]

Means for Solving the Problems The above object is achieved on a substrate by:
Equipped with an in-plane magnetic film in which the easy axis is oriented in the in-plane direction to the substrate and a perpendicular magnetic film in which the easy axis is oriented perpendicular to the substrate, and the in-plane magnetic film is provided closer to the substrate than the perpendicular magnetic film. The coercive force Hc is 1500 to 4000 Oe, the residual magnetization film thickness product BrT is 20 to 100 Gm, the coercive force Hc of the perpendicular magnetic film is 1500 to 4000 Oe, and the film thickness is 10
The problem can be solved by a magnetic recording medium of 0 to 1000 °. The thickness of the perpendicular magnetic film is 100 to 600 °
And the product Br of the residual magnetization thickness of the in-plane magnetic film.
T is preferably set to 20 to 50 Gm. It is preferable that a separation film made of a material that can grow non-epitaxially on the in-plane magnetic film is provided between the in-plane magnetic film and the perpendicular magnetic film. ~ 20
Preferably, it is 0 °. It is preferable to provide a non-magnetic intermediate layer having an hcp structure between the separation film and the perpendicular magnetic film. The distance between the in-plane magnetic film and the perpendicular magnetic film is 1
Preferably, it is set at 0 to 500 °.

[0005]

FIG. 1 shows an embodiment of a magnetic recording medium according to the present invention. The magnetic recording medium shown in FIG.
On a substrate 1, an in-plane magnetic film base film 2, an in-plane magnetic film 3, a separation film 4, a non-magnetic intermediate layer 5, a perpendicular magnetic film 6, and a protective film 7
Are sequentially formed. As the substrate 1, Ni
In addition to an aluminum alloy having a P plating film, glass,
A material made of ceramic or the like can be used. Further, the substrate 1 may have a surface that has been subjected to texture processing such as mechanical texture processing.

The in-plane magnetic film base film 2 is for orienting the c-axis of the crystal in the in-plane magnetic film 3 in the in-plane direction, and is made of Cr or a Cr alloy containing Cr as a main component. Is preferred. Particularly, Cr, Cr / Ti alloy, Cr / M
It is preferable to use an o-based alloy, a Cr / W-based alloy, or a Cr / V-based alloy. The thickness of the in-plane magnetic film base film 2 is 1
Preferably it is 0-1000 °. In this specification, the term “main component” indicates that the content of the component exceeds 50 at%.

The in-plane magnetic film 3 has its easy axis of magnetization mainly oriented in the in-plane direction. Preferred specific examples of the material of the in-plane magnetic film 3 include Co / Cr-based and Co / Cr / Ta.
System, Co / Cr / Pt / Ta system, Co / Cr / Ni / P
t / Ta-based and Co / Cr / Pt / Ta / Zr-based alloys. In particular, the content of Cr is 12 to
25 at%, the Pt content is 0 to 15 at%, the Ta content is 1 to 10 at%, the content of at least one of Zr, Re, Cu, and V is 0 to 10 at%, and the balance is Co. It is preferable to use one containing a Co alloy as a main component.

The coercive force Hc of the in-plane magnetic film 3 is 1500 to
4000 Oe (more preferably 2000 to 3500 O
e) is set in the range. When this Hc is less than 1500 Oe, the isolated waveform obtained at the time of reproduction does not become a single peak type as in the case of the perpendicular magnetic recording medium having only the perpendicular magnetic film, and is used when reproducing a general-purpose in-plane magnetic recording medium. It becomes difficult to apply the signal processing method. If Hc exceeds 4000 Oe, the recording characteristics of the in-plane magnetic film 3 deteriorate, and the output of the reproduced signal tends to decrease. Further, inconveniences such as insufficient reproduction of a single peak and an increase in noise are likely to occur.

The product BrT of the residual magnetization thickness of the in-plane magnetic film 3 is 2
0 to 100 Gm. If the BrT is less than 20 Gm, sufficient magnetic flux cannot be obtained, and the isolated waveform obtained at the time of reproduction does not become a single-peak type as in a perpendicular magnetic recording medium having only a perpendicular magnetic film. It becomes difficult to apply a signal processing method used when reproducing a medium. On the other hand, when BrT exceeds 100 Gm, medium noise increases as in the case of the longitudinal magnetic recording medium having only the longitudinal magnetic film. The worse the reproduction pulse output half width Pw _50, to obtain a sufficient output characteristics becomes difficult. BrT of in-plane magnetic film 3
Is more preferably 20 to 50 Gm. This is because when BrT is within this range, the medium noise can be further reduced.

The separation film 4 is provided for orienting the c-axis of the crystal of the perpendicular magnetic film 6 in a direction perpendicular to the substrate to improve the orientation, and is non-epitaxially grown on the in-plane magnetic film 3. Materials that can be used are used. In particular, when a material whose surface free energy is higher than the surface free energy of the constituent material of the nonmagnetic intermediate layer 5 or an amorphous material is used as this material, the nonmagnetic intermediate layer 5 and the perpendicular magnetic film formed on the separation film 4 are used. 6 to improve the crystal orientation,
This is preferable because medium noise due to disturbance of the magnetic anisotropy of the perpendicular magnetic film 6 can be minimized.

As this material, Ta, Re, CuT
It is preferable to use one or more of i, SiC, W, NiP, Zr, Ti, and C as main components. Here, CuTi means Cu and Ti
An alloy consisting of SiC refers to a material composed of Si and C. NiP refers to an alloy composed of Ni and P.

The thickness of the separation membrane 4 is preferably 5 to 200 °. If the thickness is less than 5 °, the non-magnetic intermediate layer 5 formed on the separation film 4
It is easily affected by the in-plane magnetic film 3 having the in-plane crystal orientation, the crystal orientation is disturbed, and the crystal orientation of the perpendicular magnetic film 6 formed on the non-magnetic intermediate layer 5 is disturbed. There is a possibility that the medium noise of the magnetic recording medium is increased.
On the other hand, if the thickness exceeds 200 °, the distance between the in-plane magnetic film 3 and the perpendicular magnetic film 6 increases, and the recording characteristics of the in-plane magnetic film 3 at the short recording wavelength deteriorate.

The non-magnetic intermediate layer 5 is used for further improving the crystal orientation of the perpendicular magnetic film 6, and is made of a non-magnetic material having an hcp structure.
/ Cr / Ta system, Co / Cr / Pt / X system (X: Ta,
It is preferable to use an alloy of one or more of Zr, Cu, and Re). In particular, the content of Cr is 25 to 5
It is preferable to use a material whose main component is a Co alloy having 0 at%, a Pt content of 0 to 15 at%, an X content of 0 to 10 at%, and a balance of Co. Non-magnetic intermediate layer 5
May have a single-layer structure or a multilayer structure in which a plurality of layers made of the above materials are stacked.

The thickness of the nonmagnetic intermediate layer 5 is 20 to 400 °
It is preferred that When the thickness is less than 20 °, when forming the perpendicular magnetic film 6 on the non-magnetic intermediate layer 5,
At the time of initial growth, the crystal orientation of the perpendicular magnetic film 6 is likely to be disturbed, and the medium noise of the obtained magnetic recording medium may increase. On the other hand, if the thickness exceeds 400 °, the distance between the in-plane magnetic film 3 and the perpendicular magnetic film 6 increases, and the recording characteristics of the in-plane magnetic film 3 at the short recording wavelength deteriorate.

The total thickness of the separation film 4 and the non-magnetic intermediate layer 5, that is, the distance between the in-plane magnetic film 3 and the perpendicular magnetic film 6, is 10
It is preferable to set it to 500 °. When the thickness is less than 10 °, the crystal orientation of the perpendicular magnetic film 6 tends to be disordered, and a sufficient coercive force may not be obtained. If the thickness exceeds 500 °, the distance between the in-plane magnetic film 3 and the perpendicular magnetic film 6 increases, and the recording characteristics of the in-plane magnetic film 3 at the short recording wavelength deteriorate.

The perpendicular magnetic film 6 has an axis of easy magnetization oriented mainly in a direction perpendicular to the substrate. As the material of the perpendicular magnetic film 6, Co / Cr-based, Co / Cr / Ta-based, C
o / Cr / Pt / Ta system, Co / Cr / Ni / Pt / T
An a-based or Co / Cr / Pt / Ta / Zr-based alloy can be used. In particular, the content of Cr is 16 to 30a.
t%, Pt content is 0 to 15 at%, Ta content is 2 to 10 at%, Zr content is 0 to 5 at%, and the balance is mainly composed of Co alloy. preferable.

The coercive force Hc of the perpendicular magnetic film 6 is 1500 to
4000 Oe (more preferably 2000 to 3500 O
e) is set in the range. If this Hc is less than 1500 Oe, the squareness ratio S (= residual magnetic flux density Br / saturated magnetic flux density Bs) decreases, the output also decreases, and the SNR deteriorates. If Hc exceeds 4000 Oe, the perpendicular magnetic film 6
Is not preferable because the recording characteristics of the recording medium deteriorate.

The thickness of the perpendicular magnetic film 6 is 100 to 1000
さ れ る. If the thickness is less than 100 °, a sufficient magnetic flux cannot be obtained, and the medium noise increases as in the case of the longitudinal magnetic recording medium having only the longitudinal magnetic film. The worse the reproduction pulse output half width Pw _50, to obtain a sufficient output characteristics becomes difficult. On the other hand, if the thickness exceeds 1000 °, the isolated waveform obtained at the time of reproduction does not become a single peak type, and it becomes difficult to apply a signal processing method used when reproducing a general-purpose in-plane magnetic recording medium. The thickness of the perpendicular magnetic film 6 is 100 to 600.
Å is more preferable. This is because, when the thickness is in this range, the magnetic particles in the perpendicular magnetic film 6 can be prevented from becoming coarse and the noise characteristics can be further improved.

The protective film 7 is preferably made of carbon. The thickness of the protective film 7 is preferably set to 20 to 100 °. Further, a lubricating film made of perfluoropolyether (PFPE) or the like can be formed on the protective film 7.

To manufacture the magnetic recording medium having the above structure,
First, the nonmagnetic base film 2 or the perpendicular magnetic film 6 is formed on the substrate 1 by a technique such as sputtering, vacuum deposition, ion plating, and plating. Subsequently, the protective film 7
Is formed by sputtering, a plasma CVD method, an ion beam method, or the like. To form a lubricating film on the protective film 7, a dipping method or the like can be adopted.

The magnetic recording medium having the above-described structure includes the in-plane magnetic film 3 and the perpendicular magnetic film 6, wherein the in-plane magnetic film 3 has a coercive force Hc of 1500 to 4000 Oe, and a residual magnetization film thickness product B
rT is 20 to 100 Gm, the coercive force Hc of the perpendicular magnetic film 6 is 1500 to 4000 Oe, and the film thickness is 100 to 10
Since it is assumed to be 00 °, an isolated waveform obtained at the time of reproduction does not become a dipulse, and a signal processing method used when reproducing a general-purpose in-plane magnetic recording medium can be applied.
Moreover, medium noise due to an increase in the reversal magnetization transition region and the like,
Particulate noise due to coarsening of magnetic particles is suppressed to be low, and the noise characteristics are excellent.

The separation film 4 made of a material capable of growing non-epitaxially on the in-plane magnetic film 3 is provided between the in-plane magnetic film 3 and the perpendicular magnetic film 6. The vertical orientation of the non-magnetic intermediate layer 5 and the perpendicular magnetic film 6 formed thereon is improved,
Can be increased and the medium noise can be reduced. On the other hand, the in-plane magnetic film 3 is used as the material of the separation film 4.
In the case where an epitaxial growth is used for
The orientation of the perpendicular magnetic film 6 may be disturbed by the influence of the in-plane magnetic film 3 having in-plane anisotropy.

Further, between the separation film and the perpendicular magnetic film, h
By providing a non-magnetic intermediate layer having a cp structure,
Disturbance of the orientation during the initial growth of the perpendicular magnetic film 6 can be prevented, its magnetic anisotropy can be increased, and medium noise can be reduced.

[0024]

EXAMPLES (Test Example 1) NiP plating film (thickness 1) on the surface
5 μm) formed aluminum alloy substrate (diameter 84 m)
m, thickness 0.8 mm), the surface average roughness Ra is 1
After subjecting the substrate to mechanical texture processing so as to be 5 °, the substrate 1 was set in a chamber of a DC magnetron sputtering apparatus (3010 manufactured by Anelva). The inside of the chamber was evacuated until the vacuum reached 2 × 10 ⁻⁷ Pa, and the substrate 1 was heated to 200 ° C.
-15 at% Ti-3 at% Mo (hereinafter referred to as Cr15Ti
3Mo).
0%), Co-13at% Cr-6at% Pt-3at
% Ta (Co13Cr6Pt3Ta) in-plane magnetic film 3, carbon separation film 4, Co-40 at% C
nonmagnetic intermediate layer 5 made of r (Co40Cr), Co-1
8 at% Cr-6 at% Pt-3 at% Ta (Co18
A perpendicular magnetic film 6 made of Cr6Pt3Ta) was sequentially formed by sputtering. Subsequently, a carbon protective film having a thickness of 100 ° is formed on the perpendicular magnetic film 6.
A lubricant was applied on the carbon protective film to form a lubricating film (thickness: 20 °) made of PFPE to obtain a magnetic recording medium.

(Test Examples 2 to 4) Magnetic recording media were manufactured by changing the coercive force Hc of the in-plane magnetic film 3 by changing the substrate heating temperature during film formation.

(Test Examples 5 to 10) BrT of in-plane magnetic film 3
Was changed to produce a magnetic recording medium.

(Test Examples 11 to 19) Magnetic recording media were manufactured by changing the coercive force Hc or the thickness of the perpendicular magnetic film 6.

Test Example 20 A magnetic recording medium was manufactured in the same manner as in Test Example 16 except that the separation film 4 was not formed.

Test Example 21 A magnetic recording medium was manufactured in the same manner as in Test Example 16, except that the nonmagnetic intermediate layer 5 was not formed.

Test Example 22 A magnetic recording medium was manufactured in the same manner as in Test Example 16 except that the separation film 4 and the nonmagnetic intermediate layer 5 were not formed.

The magnetostatic properties of the magnetic recording media of each of the above test examples were measured using a vibration type magnetic property measuring device (VSM). The recording and reproducing characteristics of these magnetic recording media were measured at a linear recording density of 240 kFCI using a composite type thin film magnetic head having a magnetoresistive (MR) element in the reproducing section. Table 1 shows the measurement results. SNR (Signal Nois
e Ratio), the signal amount (Signal) was measured with a solitary wave as a measurement target.

[0032]

[Table 1]

As shown in Table 1, the coercive force Hc of the in-plane magnetic film 3 is 1
The magnetic recording media of Test Examples 2 and 3 in the range of 500 to 4000 Oe had better noise characteristics than the magnetic recording media of Test Example 4 in which the coercive force Hc was set to a value exceeding the above range. I understand. In addition, while the isolated waveforms obtained during reproduction of the magnetic recording media of Test Examples 2 and 3 were unimodal, the coercive force Hc of the magnetic recording medium of Test Example 1 was set to a value below the above range. The isolated waveform obtained at the time of reproduction contained a dipulse waveform, and did not become a single peak type.

Further, the product Br of the residual magnetization thickness of the in-plane magnetic film 3
The magnetic recording media of Test Examples 6 to 8 in which T was 20 to 100 Gm had better noise characteristics than the magnetic recording media of Test Examples 9 and 10 in which BrT was set to a value exceeding the above range. I understand. In particular, BrT is 20 to
It can be seen that the magnetic recording media of Test Examples 6 and 7 set in the range of 50 Gm had better noise characteristics. In the magnetic recording media of Test Examples 6 to 8, the isolated waveform obtained at the time of reproduction was a single-peak type, whereas
The waveform obtained during reproduction of the magnetic recording medium of Test Example 5 in which rT was set to a value lower than the above range included a dipulse waveform and did not become a single-peak type.

The coercive force Hc of the perpendicular magnetic film 6 is set to 150
The magnetic recording media of Test Examples 12 and 13 with 0 Oe or more were:
Test Example 1 in which coercive force Hc was set to a value less than 1500 Oe
It can be seen that the magnetic recording medium has excellent noise characteristics as compared with the magnetic recording medium of No. 1.

Further, the thickness of the perpendicular magnetic film 6 is set to 100 to 10
The magnetic recording media of Test Examples 15 to 18 in which the thickness of the perpendicular magnetic film 6 was set outside the above range were set to 00 °.
It can be seen that the magnetic recording medium has superior noise characteristics as compared with the magnetic recording medium No. 9. Especially, the thickness is 100 ~
The magnetic recording media of Test Examples 15 and 16 set in the range of 600 ° had better noise characteristics.

In Test Examples 20 and 2 where the separation membrane 4 was not provided,
It can be seen that the magnetic recording medium having the separation film 4 was superior to the magnetic recording medium No. 2 in the noise characteristics.
Further, it can be seen that the magnetic recording medium having the nonmagnetic intermediate layer 5 was superior in the noise characteristics to the magnetic recording media of Test Examples 21 and 22 in which the nonmagnetic intermediate layer 5 was not provided.

[0038]

As described above, in the magnetic recording medium of the present invention, the signal processing method used when reproducing a general-purpose in-plane magnetic recording medium can be applied, and the magnetic recording medium has excellent noise characteristics. It will be.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing one embodiment of a magnetic recording medium of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 3 ... In-plane magnetic film, 4 ... Separation film, 5 ... Non-magnetic intermediate layer, 6 ... Perpendicular magnetic film

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Sakai 5-1 Yawata Kaigandori, Ichihara-shi, Chiba Prefecture Showa Denko HD Research & Development Center (72) Inventor Tetsuya Osaka 3-4-1 Okubo Shinjuku-ku, Tokyo No. School of Science and Engineering, Waseda University

Claims (7)

[Claims] 1. An in-plane magnetic film having an easy axis of magnetization oriented in the in-plane direction with respect to the substrate, and a perpendicular magnetic film having an easy axis of magnetization oriented perpendicular to the substrate, wherein the in-plane magnetic film is formed on the substrate. The coercive force Hc of the perpendicular magnetic film is 1500 to 4000 Oe, the coercive force Hc of the perpendicular magnetic film is 1500 to 4000 Oe, and the film thickness is 100 to 4000 Oe. A magnetic recording medium having a thickness of 1000 °. 2. The magnetic recording medium according to claim 1, wherein
A magnetic recording medium, wherein the perpendicular magnetic film has a thickness of 100 to 600 °. 3. The magnetic recording medium according to claim 1, wherein a product BrT of a residual magnetization thickness of the in-plane magnetic film is 20 to 5.
A magnetic recording medium having a thickness of 0 Gm. 4. The magnetic recording medium according to claim 1, wherein the non-epitaxial growth can be performed between the in-plane magnetic film and the perpendicular magnetic film with respect to the in-plane magnetic film. A magnetic recording medium provided with a separation film made of various materials. 5. The magnetic recording medium according to claim 4, wherein
A magnetic recording medium, wherein the thickness of the separation film is 5 to 200 °. 6. The magnetic recording medium according to claim 4, wherein a nonmagnetic intermediate layer having an hcp structure is provided between the separation film and the perpendicular magnetic film. 7. The magnetic recording medium according to claim 1, wherein a distance between the in-plane magnetic film and the perpendicular magnetic film is 10 to 500 °.