JPH087250A - Magnetic recording medium and magnetic storage device using this medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium using a smooth substrate and having high intransurface magnetic anisotropy,and high coercive force and a magnetic storage device using the medium. CONSTITUTION:When a nonmagnetic underlayer 12, a magnetic layer 13 and a protective layer 14 are successively laminated on a nonmagnetic substrate 11 to obt.ain a magnetic recording medium, the substrate 11 is made of a substrate of glass, carbon, silicon, etc., having a smooth surface, the angle of inclination of columnar grains constituting the underlayer 12 is regulated to the range of 20-50 deg. from the normal direction of the substrate 11 and the ratio (t1/t2) of the thickness (t1) of the magnetic layer 13 to the thickness (t2) of the underlayer 12 is regulated to <=0.2. High density recording is possible.

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 a magnetic storage device, and more particularly to a thin film type recording medium suitable for high density magnetic recording, and a small and large capacity magnetic storage device using the thin film type recording medium.

[0002]

2. Description of the Related Art With the downsizing of computers, there is a strong demand for miniaturization, large capacity, and high speed access of magnetic disk devices and other external storage devices. In particular, the magnetic disk recording device is a storage device suitable for high-density and high-speed recording, and its demand is further increasing. As a magnetic recording medium used in a magnetic disk device, a coating type recording medium in which a powder of an oxide magnetic material is coated on a disk substrate and a thin film type in which a thin film of a metal magnetic material is deposited on the substrate by a method such as sputtering are used. A recording medium is known.

This thin film type recording medium is suitable for high density recording since the density of the magnetic substance in the recording film is higher than that of the coating type recording medium. An Al (aluminum) alloy coated with a Ni-P plated film is usually used for the substrate of the thin film medium, and further, head adhesion on the substrate surface and in-plane magnetic anisotropy with the direction of the substrate as the easy axis of magnetization. For the purpose of application, grooves or protrusions called texture having a surface center line average roughness of about 2 nm to 100 nm are formed.

At present, a magnetic disk device using an Al alloy substrate which has been put into practical use realizes a high recording density by utilizing in-plane magnetic anisotropy. On the other hand, along with the miniaturization of magnetic disk devices, the magnetic disk devices have been incorporated into portable computers such as note type personal computers, so that the demand for shock resistance of the disks has been further increased. Since the Al (aluminum) alloy substrate used conventionally has insufficient hardness of the Al (aluminum) alloy, the disc may be damaged when the head collides with the disc. Therefore, a glass substrate having excellent impact resistance has attracted attention, but it has a problem that the surface is hard and texture processing is difficult.

The problem of head adhesion can be solved by forming isotropic irregularities on the substrate or the protective film, but this method cannot provide in-plane magnetic anisotropy. As a method for imparting in-plane magnetic anisotropy on a smooth substrate, an oblique vapor deposition method (for example, JP-A-58-128023) or an oblique sputtering method (for example, JP-A-62-82516, JP-A-62-150516). Japanese Laid-Open Patent Publication No. 4-182925
Although an oblique incidence method such as that disclosed in Japanese Laid-Open Patent Publication No. 2004-242242 is known, in-plane magnetic anisotropy can be imparted, but the maximum in-plane coercive force is 1.6.
Low as kOe or less, high density magnetic recording medium (for example, 2G
2k to achieve an areal recording density of b / inch ^2.
Oe or more in-plane coercive force is required).

[0006]

Magnetic disk devices using a glass substrate having excellent impact resistance have begun to be commercialized, but the areal recording density is lower than that of a magnetic disk device using an Al (aluminum) alloy substrate. is the current situation. One of the causes is that the in-plane magnetic anisotropy cannot be imparted as described above. In the future, in order to achieve an areal recording density equal to or higher than that of a magnetic disk device using an Al (aluminum) alloy substrate in a magnetic disk device using a substrate such as glass, carbon, or silicon whose surface is extremely smooth. It is necessary to form a magnetic recording medium having strong in-plane magnetic anisotropy and high in-plane coercive force.

In view of the above problems and circumstances in the prior art, the first object of the present invention is to provide a magnetic recording medium having a substrate having an extremely smooth surface and having strong in-plane magnetic anisotropy and high coercive force. A second object is to provide a large capacity and highly reliable magnetic storage device using such a medium.

[0008]

In order to achieve the first object of the present invention, in a magnetic recording medium comprising a nonmagnetic underlayer, a magnetic layer and a protective layer sequentially laminated on a nonmagnetic substrate, The magnetic substrate consists of a substrate with a smooth surface,
The nonmagnetic underlayer is composed of columnar particles, and the inclination angle of the columnar particles is 20 ° or more from the normal direction of the nonmagnetic substrate, 50
The thickness ratio (t ₁ / t ₂ ) of the thickness (t ₁ ) of the magnetic layer and the thickness (t ₂ ) of the non-magnetic underlayer is 0.2 or less. Further, (1) the thickness (t ₁ ) of the magnetic layer is 10
The thickness is in the range of 30 nm or more and 30 nm or less, and (2) the thickness (t ₂ ) of the nonmagnetic underlayer is 100 nm or more and 300 nm.
Most preferably, it is in the following range, (3) the non-magnetic underlayer is formed by the oblique vapor deposition method or the oblique sputtering method, and (4) the substrate is made of glass, carbon, or silicon.

In order to achieve the above-mentioned second object, magnetic recording is performed by using the above-mentioned magnetic recording medium, a composite magnetic head in which a recording electromagnetic induction type thin film magnetic head and a reproducing magnetoresistive effect type magnetic head are combined. Configure the device. Further, it is desirable to use the signal processing means by the maximum likelihood decoding method as the signal processing means for the magnetic storage device because the recording density can be further improved.

[0010]

When the nonmagnetic underlayer is formed by the oblique vapor deposition method or the oblique sputtering method, the film structure of the nonmagnetic underlayer has a columnar structure, and the columnar particles 21 grow while being inclined in the vapor incident direction. The inclination angle of the columnar particles, 20 ° or more from the non-magnetic substrate normal direction, 50 ° or less, the thickness of the magnetic layer (t ₁₎ and the thickness ratio of the thickness of the nonmagnetic layer (t ₂₎ (t ₁ / t ₂ )
Is set to be 0.2 or less, the particles of the magnetic layer grow while continuing the shape of the columnar particles 21 of the non-magnetic underlayer, as shown in the three-dimensional schematic view of FIG.

A direction 26 orthogonal to the vapor incident direction 24 (hereinafter referred to as an orthogonal direction, and as shown in FIG. 4, the orthogonal direction 46 is defined by the vapor incident surface 42 and an average surface formed by the magnetic layers. The direction given by the line of intersection (hereinafter parallel direction 45
(Which is a direction orthogonal to the direction)).
A plurality of 2 (on average, 2 to 3) are connected in the vertical direction 26 to form a cluster 23. On the other hand, parallel direction 2
5 (corresponding to the parallel direction 45 in FIG. 4) has the step of the columnar particles 21 of the non-magnetic underlayer, the adjacent particles of the magnetic layer are not connected between the steps. That is, within the same step, a plurality of magnetic layers 22 formed on each columnar particle 21 in the orthogonal direction 26 are connected to each other to form a cluster 23.

Since the cluster 23 has an anisotropic shape whose major axis is the direction orthogonal to the vapor incident direction (orthogonal direction 26), uniaxial anisotropy is induced by so-called shape magnetic anisotropy, and the magnetic layer surface is formed. Magnetic anisotropy is imparted in which the direction perpendicular to the vapor incident direction is the easy axis of magnetization. Further, by setting the film thickness of the nonmagnetic underlayer to 100 nm or more and 300 nm or less, the size of the columnar particles of the nonmagnetic underlayer is made uniform, and further, the film thickness of the magnetic layer is set to 10 nm or more and 30 nm or less. As a result, the cluster size is less susceptible to thermal fluctuations and behaves like single domain particles. As a result, a high coercive force is obtained, the dispersion of the magnetization state (variation in the magnetization direction) is reduced, and the medium noise is reduced.

Since the magnetic recording medium of the present invention can suppress the medium noise to a low level, by using a composite magnetic head in which a recording electromagnetic induction type thin film magnetic head and a reproducing magnetoresistive effect type magnetic head are combined, A recording density of 1 gigabit per square inch can be realized.

[0014]

EXAMPLE As shown in FIG. 1, a non-magnetic underlayer 12, a magnetic layer 13 and a protective layer 14 are sequentially formed on a non-magnetic substrate 11 by an oblique vapor deposition method or an oblique sputtering method. The magnetic layer 13 and the protective layer 14 may be formed by an ordinary vapor deposition method or sputtering method. At this time, the substrate temperature is preferably 100 ° C. or higher and 300 ° C. or lower, and the vapor incident angle is preferably 40 ° or more and 70 ° or less from the normal direction of the non-magnetic substrate.

In order to form a magnetic recording medium having a strong in-plane magnetic anisotropy and a high in-plane coercive force, the film structure of the magnetic layer 13 is made to be an anisotropic cluster structure in which a plurality of magnetic particles are connected, and It is effective to reduce the magnetic interaction between adjacent clusters. In order to realize such a film structure, the film structure of the non-magnetic underlayer 12 has a columnar structure,
Columnar particles inclined angle from the non-magnetic substrate normal direction 20 ° or more, and than 50 °, yet thickness ratio (t ₁ the thickness of the magnetic layer (t ₁₎ and the film thickness of the nonmagnetic layer (t ₂₎ / T ₂ ) is 0.2
The following is desirable. The thickness of the non-magnetic underlayer is 10
0 nm or more and 300 nm or less, the thickness of the magnetic layer is 10 nm
As described above, the range of 30 nm or less is desirable in order to make the cluster sizes uniform. The lubricating layer 15 is finally formed on the protective layer 14. Hereinafter, examples of the magnetic recording medium of the present invention will be described in detail.

Example 1 As shown in FIG. 3, a 200 nm Cr underlayer 32 is formed on a substrate 31 made of a tempered glass substrate (Corning 0313) having an outer diameter of 95 mmφ and a surface center line average roughness of 1.4 nm. A Co magnetic layer 33 having a thickness of 10 nm to 30 nm and a carbon protective layer 34 having a thickness of 10 nm were formed by an oblique evaporation method, and finally a lubricating layer 35 of a perfluoroalkylpolyether system having a thickness of 3 nm was formed. The vapor incident angles were 45 ° and 70 ° with respect to the substrate normal direction. The degree of vacuum before vapor deposition is 2 × 10 ^-6 Torr, and the substrate temperature is 300.
℃, vapor deposition rate of Cr underlayer (0.5nm ~ 1.0n
m) / s, Co magnetic layer and carbon protective film (0.05
nm-1.0 nm) / s.

As Comparative Example 1, the vapor incident angle was 20.
As a comparative example 2, a magnetic recording medium having a Co magnetic layer thickness of 50 nm or more was manufactured under the same conditions as in Example 1. Here, in the medium of Example 1 and Comparative Example 1, the film thickness of the magnetic layer (t ₁₎ and the thickness ratio of the thickness of the nonmagnetic underlayer _{(t 2) (t 1 /} t 2) 0.2 Hereinafter, in the medium of Comparative Example 2, the above film thickness ratio is 0.2 or more.

The in-plane coercive forces of the magnetic recording media of Example 1 and Comparative Examples 1 and 2 were measured using a sample vibrating magnetometer (VSM). Here, the maximum applied magnetic field was 13 kOe.
As shown in FIG. 4, the in-plane coercive force was measured in two directions, that is, the direction along the vapor incident direction (parallel direction 45) and the direction (orthogonal direction 46) in the film plane. Parallel direction 45
In other words, the orthogonal direction 46, in other words, the parallel direction 45 is the vapor incident surface 42 (the vapor incident direction 44 at a predetermined position on this surface).
Is arranged with a predetermined vapor incident angle from the normal axis of the surface 41) and the average surface 41 formed by the magnetic layer.
The orthogonal direction 46 is a direction orthogonal to the parallel direction 45.

FIG. 5 shows the in-plane coercive force measured in the film surface in the parallel direction 45 along the vapor incident direction, and FIG. 6 shows the in-plane coercive force measured in the orthogonal direction 46 orthogonal to the vapor incident direction in the film surface. The in-plane coercive force is shown. Hereinafter, in FIG. 5, FIG. 6, and FIG. 7, points □, points Δ (same as black-painted points Δ), and points ○ (same as black-painted points ○) have vapor incident angles of 20 °,
It shows that they are 45 ° and 70 °. Further, in FIG. 5, two points of Example 1 (points of black coating Δ, points of black coating ○) and points ○ and points □ in Comparative Example 3 overlap each other when the thickness of the Co magnetic layer is about 30 nm. Further, in FIG. 6, point ◯ and point Δ in Comparative Example 3 when the film thickness of the Co magnetic layer is about 30 nm almost overlap.

When the film thickness of the Co magnetic layer is in the range of 10 nm to 30 nm and the vapor incident angles are 45 ° and 70 °,
A high in-plane coercive force was obtained, and a high in-plane coercive force of 1700 Oe or more and 2983 Oe at maximum was obtained in the direction orthogonal to the vapor incident direction. The vapor incident angle of Comparative Example 1 was 20.
The maximum in-plane coercive force of the medium is 1500 Oe.
Did not reach The thickness of the Co magnetic layer of Comparative Example 2 was 5
The in-plane coercive force of the medium of 0 nm or more was as low as 1100 Oe or less.

Next, in order to investigate the in-plane magnetic anisotropy of Example 1 and Comparative Examples 1 and 2, the torque curve was measured.
Here, the applied magnetic field was 13 kOe. Torque curve s
The in (2θ) component is divided by the volume of the Co magnetic film to obtain the in-plane magnetic anisotropy energy, and the result is shown in FIG. 7. In FIG. 7, Comparative Example 3 in which the thickness of the Co magnetic layer is about 30 nm
The points ○, △, and □ in are almost overlapped. The medium of Example 1 exhibits uniaxial magnetic anisotropy in which the easy magnetization axis is in the direction orthogonal to the vapor incident direction in the film surface, and 8 × 10 ⁵ erg / c
A high magnetic anisotropy energy of c or more and a maximum of 1 × 10 ⁶ erg / cc was obtained. On the other hand, the medium having a vapor incident angle of 20 ° in Comparative Example 1 has a maximum of 5 × 10 ⁵ er.
It did not reach g / cc. The magnetic anisotropy energy of the medium of Comparative Example 2 having a Co magnetic layer thickness of 50 nm or more
Was less than 7 × 10 ⁵ erg / cc, which was lower than that of the medium of Example 1.

As a result of observing the cross-sectional morphology of the medium of Example 1 and Comparative Example 1 with a scanning electron microscope, the Cr underlayer of the medium of Example 1 has a clear columnar structure, and the inclination angle of the columnar particles is Was in the range of 20 ° or more and 50 ° or less from the normal direction of the substrate. On the other hand, no clear columnar structure was found in the Cr underlayer of the medium of Comparative Example 1.

From the above, in order to manufacture a magnetic recording medium having a strong in-plane magnetic anisotropy and a high coercive force, the inclination angle of the columnar particles of the non-magnetic underlayer is set to 20 from the direction normal to the substrate. degrees or more, the range of than 50 °, and that the thickness ratio of the thickness of the magnetic layer (t ₁₎ and the film thickness of the nonmagnetic underlayer (t ₂₎ of (t ₁ / t ₂₎ to 0.2 or less Proved to be effective.

In order to clarify the effect of the Cr underlayer on the in-plane coercive force and magnetic anisotropy, in Comparative Example 3, the Cr underlayer was not formed and Co of 30 n was directly deposited on the glass substrate.
The in-plane coercive force and magnetic anisotropy energy of the medium having a thickness of m were measured. The results are shown in FIGS. 5, 6 and 7.
The in-plane coercive force of the medium of Comparative Example 3 in which the Cr underlayer is not formed almost does not depend on the vapor incident angle and shows a small value of about 500 Oe, and the magnetic anisotropy energy is 1 × 10.
^It was as small as ⁵ erg / cc or less. That is, it was found that the Cr underlayer plays a role of increasing the in-plane coercive force and imparting magnetic anisotropy.

(Embodiment 2) An embodiment of the magnetic storage device of the present invention will be described in detail below. An outer diameter 9 having a surface center line average roughness of 1.4 nm, as in Example 1.
200 nm Cr underlayer, 10 nm Co magnetic layer, 10 nm on a 5 mmφ tempered glass substrate (Corning 0313).
A carbon protective layer having a thickness of 3 nm was formed by an oblique vapor deposition method, and finally a lubricating layer of a perfluoroalkylpolyether having a thickness of 3 nm was formed. In addition, as shown in FIG.
2 is covered with a mask 73 partially having an opening, the glass substrate 72 is fixed by the substrate holder 71 and the substrate fixing member 71 ′, the glass substrate 72 is rotated, and the vapor incident angle from the evaporation source 74 is adjusted to It was set to be inclined by 45 ° with respect to the normal direction in the radial direction of the substrate. Degree of vacuum before vapor deposition,
The substrate temperature and the vapor deposition rate are the same as the conditions of Example 1.
A magnetic storage device was manufactured by incorporating one to ten magnetic recording media thus obtained. 9A and 9B are a schematic plan view and a sectional view of the magnetic memory device, respectively. This apparatus has a well-known configuration including a magnetic recording medium 81, a drive unit 82 for rotating the magnetic recording medium 81, a magnetic head 83, a driving unit 84 for the magnetic head 83, and a recording / reproducing processing unit 85 for the magnetic head 83. It is a magnetic storage device. As the magnetic head 83, a composite magnetic head in which a recording electromagnetic induction thin film magnetic head and a reproducing magnetoresistive magnetic head are combined is used, and a recording density of 1 gigabit per square inch can be realized.

In each of the above embodiments, C is used as the magnetic layer.
o was used, but CoNiCr, CoCr instead of Co
Similar results were obtained using Co-based alloys such as Ta and CoCrPt. Similar results can be obtained by using a carbon substrate or a silicon substrate instead of the glass substrate as the flat substrate, and the surface center line average roughness of the flat substrate is preferably 2 nm or less.

[0027]

According to the present invention, there are provided a magnetic recording medium capable of high density recording on a substrate having a smooth surface such as glass, carbon and silicon, and a compact and large capacity magnetic storage device using the same. Can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic cross section of a magnetic recording medium of the present invention.

FIG. 2 is a diagram schematically showing an interface portion between a magnetic layer and a non-magnetic underlayer of the magnetic recording medium of the present invention.

FIG. 3 is a diagram schematically showing a cross section of a magnetic recording medium according to an embodiment of the present invention.

FIG. 4 is a diagram showing definitions of a vapor incident angle and a measurement direction of in-plane coercive force according to an embodiment of the present invention.

FIG. 5 is a diagram showing the relationship between the vapor incident direction of the magnetic recording medium of one embodiment of the present invention, the in-plane coercive force in the parallel direction, and the film thickness of the Co magnetic layer.

FIG. 6 is a diagram showing the relationship between the vapor incident direction of the magnetic recording medium of one embodiment of the present invention, the in-plane coercive force in the orthogonal direction, and the film thickness of the Co magnetic layer.

FIG. 7 is a diagram showing the relationship between the magnetic anisotropy energy and the Co film thickness of the magnetic recording medium of one embodiment of the present invention.

FIG. 8 is a diagram showing the relationship between the substrate and the vapor incident direction of the magnetic recording medium of one embodiment of the present invention.

9A is a plan view schematically showing a magnetic memory device according to an embodiment of the present invention, and FIG. 9B is a cross-sectional view taken along the line AA ′ in FIG.

[Explanation of symbols]

11 ... Non-magnetic substrate, 12, 21 ... Non-magnetic underlayer, 13,
22 ... Magnetic layer, 14 ... Protective layer, 15, 35 ... Lubrication layer, 2
3 ... Cluster, 24, 44 ... Vapor incident direction, 31, 72
... Glass substrate, 32 ... Cr underlayer, 33 ... Co magnetic layer,
34 ... Carbon protective layer, 41 ... Average surface formed by magnetic layer, 42 ... Vapor incident surface, 43 ... Vapor incident angle, 44 ... Vapor incident direction, 25, 45 ... Parallel direction, 2
6, 46 ... Orthogonal direction, 71 ... Substrate holder, 71 '... Substrate fixing member, 73 ... Mask, 74 ... Evaporation source, 81 ... Magnetic recording medium, 82 ... Magnetic recording medium drive section, 83 ... Magnetic head, 84 ... Magnetic Head drive unit, 85 ... Recording / reproducing signal processing system.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaaki Ninomoto 1-280, Higashikoigokubo, Kokubunji, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd.

Claims (6)

[Claims] 1. A magnetic recording medium in which a nonmagnetic underlayer, a magnetic layer and a protective layer are sequentially laminated on a nonmagnetic substrate,
The non-magnetic substrate is a substrate having a smooth surface, the non-magnetic underlayer is composed of columnar particles, and the inclination angle of the columnar particles is 20 ° from the normal direction of the non-magnetic substrate.
It is in the range of 50 ° or less and the film thickness of the magnetic layer (t
₁ ) and the film thickness (t ₂ ) of the non-magnetic underlayer (t ₁ /
The magnetic recording medium is characterized in that t ₂ ) is 0.2 or less. 2. The thickness of the magnetic layer is 10 nm or more and 30 n
The magnetic recording medium according to claim 1, wherein the magnetic recording medium is in a range of m or less. 3. The magnetic recording medium according to claim 1, wherein the thickness of the nonmagnetic underlayer is in the range of 100 nm or more and 300 nm or less. 4. The magnetic recording medium according to claim 1, wherein the nonmagnetic underlayer is formed by an oblique vapor deposition method or an oblique sputtering method. 5. The magnetic recording medium according to claim 1, wherein the non-magnetic substrate is made of glass, carbon or silicon. 6. A magnetic storage device comprising a magnetic recording medium, a rotary drive unit for rotationally driving the magnetic recording medium, a magnetic head, a magnetic head drive unit, and a recording / reproducing signal processing system. The magnetic recording medium according to any one of claims 1 to 5.
A magnetic storage device, which is the magnetic recording medium according to any one of 1.