JP2002123930A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium for ultrahigh-density recording exceeding 50 Gb/in2 and having low S/N. SOLUTION: In the magnetic recording medium having a magnetic recording layer on a nonmagnetic substrate, a nonmagnetic layer having a hcp crystalline structure is formed on one surface of the nonmagnetic substrate, and first, second and third base layers are formed in this order on the nonmagnetic layer. Then the magnetic recording layer is formed on the third base layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk drive for storing a large amount of information quickly and accurately. More specifically, the present invention relates to a structure of a magnetic recording medium for a magnetic disk having high performance and high reliability, and further relates to a magnetic disk and a magnetic disk device using the magnetic recording medium.

[0002]

2. Description of the Related Art In recent years, there has been a remarkable progress in the advanced information society, and multimedia in which various forms of information are integrated has rapidly spread. One of the information recording devices supporting this is a magnetic disk device (for example, a hard disk device).

At present, the magnetic disk drive is being downsized while improving the recording density. At the same time, the cost of disk devices has been rapidly reduced. By the way, in order to increase the recording capacity of the magnetic disk, the distance between the disk and the magnetic head must be reduced.
Increasing the coercive force of the medium, devising a signal processing method, developing a medium with small thermal fluctuation,
Are essential technologies.

In particular, in a magnetic recording medium, an increase in coercive force is indispensable for realizing high-density magnetic recording. In addition, in order to achieve a surface recording density exceeding 50 Gb / in ² , it is necessary to further reduce the unit (cluster) in which magnetization reversal occurs during recording or erasing, and to precisely control the distribution. Such control reduces noise generated from the medium during reproduction,
Furthermore, it is becoming important from the viewpoint of reducing thermal fluctuation. As a method for achieving these, for example, US Pat. No. 4,652,499 proposes to provide a seed film under a magnetic film.

Further, in order to realize high-density recording, if it is attempted to form minute magnetic domains in both the track direction and the radial direction of the magnetic disk, the magnetic head must have a narrow magnetic gap or a narrow track width. It is necessary to manufacture a head that has been subjected to precise fine processing. For this reason,
Attempts have been made to improve processing accuracy by using a processing method such as a focused ion beam (FIB) method. However, the higher the processing accuracy, the lower the yield as a product or the longer the processing time.

In the above prior art, there is a limit in controlling the crystal grain size and the distribution thereof in the information recording ferromagnetic thin film formed via the seed film.
In order to realize a recording density exceeding Gb / in ² , medium noise and thermal fluctuation may not be sufficiently suppressed. This is because even if the crystal grains of the magnetic film are refined in order to obtain a grain size of about 10 nm even if the seed film material is selected and the manufacturing conditions and the structure are optimized, particles that are roughly twice as large as 10 nm, Conversely, particles fined to about 1/2 of 10 nm were mixed. The distribution was also Gaussian with a wide base.

[0007] Among them, crystal grains larger than the average lead to an increase in noise when recording / reproducing. Conversely, particles smaller than the average increase the thermal fluctuation when recording / reproducing. In addition, due to the magnetic interaction between the magnetic crystal grains, the size of the magnetization reversal was remarkably increased to 5 to 10 grains. Therefore, ideally, one bit of the magnetization reversal size can be represented by one crystal grain.

[0008] For that purpose, it is necessary to establish a technique capable of significantly reducing magnetic interaction and precisely controlling the grain size centered on the average value of crystal grains of 10 nm for practical use of ultra-high density magnetic recording. It was important. Furthermore, in order to allow the minute magnetic domains to exist stably, it was necessary to develop a medium having a large magnetic anisotropy and a high coercive force. However, there is a limit to the magnetic field intensity that can be output from the magnetic head, and there are cases where normal recording cannot be performed.

[0009] The thickness of the magnetic film has been rapidly reduced with the progress of high density. As a result, if the crystal orientation of the magnetic film was insufficient, the magnetic properties deteriorated, such as a sudden decrease in coercive force. In this regard, there is a limit in improving the characteristics by adjusting the composition of the magnetic film.

[0010]

Accordingly, the first aspect of the present invention is as follows.
It is an object of the present invention to provide a high-performance magnetic recording medium which improves crystal orientation by reducing the crystal grain size in a magnetic film, generates less noise, and has excellent signal resolution. A second object of the present invention is to provide a magnetic recording medium having low noise, low thermal fluctuation, and low thermal demagnetization by suppressing dispersion of crystal grain size. A third object of the present invention is to provide a magnetic recording medium suitable for high-density magnetic recording by controlling the crystal orientation of a magnetic film. A fourth object of the present invention is to provide a magnetic recording medium suitable for high-density recording by reducing the magnetic interaction between magnetic particles to reduce the unit of magnetization reversal during recording or erasing. . A fifth object of the present invention is to provide an ultra-high-density recording medium exceeding 50 Gb / in ² ,
And an information recording apparatus using the same.

[0011]

The object of the present invention is to provide a magnetic recording medium having at least a magnetic recording layer on a non-magnetic substrate, wherein the crystal structure is hcp on one surface of the non-magnetic substrate.
A non-magnetic layer having a structure is formed, a first, second and third underlayers are formed in this order on a surface of the non-magnetic layer, and the magnetic recording layer is formed on the third underlayer. The problem is solved by a magnetic recording medium on which a layer is formed. In particular, the first
The magnetic recording medium in which the underlayer described above is formed by the ECR sputtering method is preferable.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a magnetic recording medium according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic sectional view of an example of the magnetic recording medium 1 of the present invention. As shown in the drawing, the magnetic recording medium 1 of the present invention has a nonmagnetic layer 5 having a hcp structure on one surface of a nonmagnetic substrate 3. A first underlayer 7 is provided, a second underlayer 9 is provided thereon, and a third underlayer 11 is sequentially provided on the surface of the second underlayer 9. A magnetic recording layer 13 is provided on the upper surface of the third underlayer 11, and a protective layer 15 is provided on the upper surface of the magnetic recording layer 13.

In the magnetic recording medium 1 of the present invention, the nonmagnetic layer 5 having the hcp structure is first formed on the surface of the nonmagnetic substrate 3.
Is formed, the magnetic recording layer 13 is interposed through a plurality of underlayers.
By forming, the crystal grain size in the magnetic recording layer is reduced and the crystal orientation is improved. As a result, it is possible to obtain a high-performance magnetic recording medium with little noise and excellent signal resolution.

The non-magnetic layer 5 is mainly composed of Co.
Is preferably formed from an alloy material containing at least one element selected from the group consisting of Cr, Ru, Zr, Ta, Nb and V.

The nonmagnetic layer 5 can be formed, for example, by a DC magnetron sputtering method or a conventional vapor deposition method. If desired, the film can be formed by an ECR sputtering method.

When the nonmagnetic layer 5 is formed by using the DC magnetron sputtering method, the power applied to the target may be adjusted so that the film forming rate is 0.5 nm / sec or more. This is because, at a deposition rate of less than 0.5 nm / sec, the possibility of taking in impurities during film formation becomes large,
This is because the quality of the formed film is likely to be deteriorated. The upper limit of the film forming rate is determined by the performance of the film forming apparatus (the upper limit of the applied power, the cooling efficiency of the target, the controllability of the process time, etc.) and the film quality of the formed film (film thickness distribution in the substrate, setting film). Value from the thickness).
I can't decide it. The substrate temperature during film formation may be lower than or equal to the substrate temperature when forming the magnetic recording layer 13. In particular, it is more desirable to form the nonmagnetic layer 5 near room temperature from the viewpoint of reducing the particle size of the film formed on the nonmagnetic layer 5. The gas pressure at the time of forming the nonmagnetic layer 5 is 2 m
The pressure is preferably in the range of Torr to 20 mTorr. Gas pressure is 20
If the pressure exceeds mTorr, the shadowing effect increases the tendency for the crystal grains of the formed film to be physically isolated, and the unevenness of the film surface increases. On the other hand, the lower limit of the gas pressure may be any gas pressure at which the plasma during sputtering is stably discharged. In the film deposition system used in this study, 2 mTorr
Was the limit for stable discharge. Almost the same concept can be applied to other film forming methods. Under these conditions, the crystal structure of the non-magnetic layer 5 can be an hcp structure.

The thickness of the nonmagnetic layer 5 is generally 2 nm to 2 nm.
Preferably, it is within the range of 0 nm. If the thickness is less than 2 nm, not only is it difficult to form a uniform non-magnetic layer, but also the effect of reducing the crystal grain size and improving the crystal orientation in the magnetic recording layer, which is the purpose of using the non-magnetic layer, is not satisfactory. Will be enough. On the other hand, when the film thickness is more than 20 nm, the effect of miniaturizing the crystal grain size and improving the crystal orientation in the magnetic recording layer is only saturated and uneconomical. More preferably, the thickness of the nonmagnetic layer 5 is in the range of 5 nm to 17 nm.

The first underlayer 7 is formed of, for example, b. c. c. It is formed from a base material or a B2-based material. b. c. c.
As the system material, Cr, V, Mo, W, N
Alloys to which at least one element selected from the group consisting of b, Ti, Ta, Ru, Zr, and Hf are added can be used. Further, as the B2-based material, a Ni-Al alloy or the like can be used. The crystal structure of the first underlayer 7 is preferably a body-centered cubic lattice (bcc) structure or a B2 structure. By disposing the first underlayer 7 having such a crystal structure, each of the layers formed thereon is epitaxially grown while inheriting the crystallinity and crystal orientation of the first underlayer. Of the Co alloy that constitutes
The effect of improving the magnetic characteristics and recording / reproducing characteristics of the medium can be obtained by directing the axis parallel to the film surface. Therefore, the purpose of use of the first underlayer 7 is to control the orientation of the ferromagnetic particles forming the magnetic recording layer 13.

The thickness of the first underlayer 7 is generally 5 nm.
25 nm. The thickness of the first underlayer 7 is 5
If it is less than nm, a film having uniform crystal orientation and good crystallinity will not be formed, and the intended purposes of controlling the crystal grain size, controlling the distribution, and controlling the orientation cannot be sufficiently achieved. on the other hand,
When the thickness of the first underlayer 7 is more than 25 nm, the crystal grain size grows and grows, and the crystal grain size distribution also increases.
This is problematic in that the crystal grains are refined or the crystal grain size distribution is homogenized.

It is particularly preferable that the first underlayer 7 is formed by ECR sputtering. When the ECR sputtering method is used to form the first underlayer 7, a film having high orientation, fine crystal grains, and small particle size dispersion can be obtained. Thereby, each layer formed on the upper surface is epitaxially grown while inheriting the crystal orientation, crystal grain size and grain size distribution of the first underlayer, so that the c-axis of the Co alloy constituting the magnetic recording layer is parallel to the film plane. In addition to improving the magnetic characteristics and recording / reproducing characteristics of the medium, the particle size distribution of the magnetic crystal grains is reduced, and the crystallinity of the magnetic crystal grains is improved. The effect is obtained.

The second underlayer 9 is formed of, for example, b. c. c. It is formed from a system material or the like. b. c. c. As the system material, Cr, Cr, V, Mo, W, Nb, Ti, Ta,
Alloys to which at least one element selected from the group consisting of Ru, Zr, and Hf is added can be used. Similarly,
Ni-Al alloys can also be used. Cr-Ti or Cr-M
o is preferred. The crystal structure of the second underlayer 9 is preferably a body-centered square lattice (bct) or a body-centered cubic lattice (bcc). Crystal structures with a body-centered cubic lattice (bcc) are particularly preferred. With the second underlayer 9 having such a specific crystal structure, the second underlayer 9 can be epitaxially grown on the first underlayer 7. Therefore, the purpose of using the second underlayer 9 is to control the orientation of the ferromagnetic particles forming the magnetic recording layer and to match the lattice.
The first underlayer and the second underlayer can be formed of the same material or different materials. In the case where the first underlayer and the second underlayer are formed of the same material, if the film thickness corresponding to (the first underlayer + the second underlayer) is formed at once, the crystal grains grow and grow. Therefore, when the first underlayer is formed, the film formation is stopped once, and then the next second underlayer is formed, there is an advantage that enlargement of crystal grains can be prevented by providing an interval in the middle. .

The thickness of the second underlayer 9 is generally 3 nm.
25 nm. The thickness of the second underlayer 9 is 3
When the thickness is less than nm, the second underlayer 9 cannot be formed uniformly on the first underlayer 7, and the intended purpose of controlling the crystal grain size and the orientation can be sufficiently achieved. Can not. On the other hand, when the thickness of the second underlayer 9 is more than 25 nm,
Since the crystal grain size grows and grows and the crystal grain size distribution also increases, there is a problem in that the crystal grain size is reduced and the crystal grain size distribution is homogenized.

The second underlayer 9 is formed by ECR sputtering, DC
The film can be formed by a magnetron sputtering method, a vapor deposition method, or the like.

The crystal structure of the first underlayer is B2 or bcc
It is preferable that the crystal structure of the second underlayer is bct or bcc, and that the second underlayer is substantially epitaxially grown on the first underlayer. Further, the first underlayer and the second underlayer each have substantially the same crystal orientation,
Most preferably, the (211) plane or the (100) plane of each underlayer is substantially parallel to the nonmagnetic substrate. Further, the first underlayer and the second underlayer have an epitaxial growth relationship, and the length of the lattice in the in-plane direction of the crystal plane substantially parallel to the nonmagnetic substrate in the first underlayer. To L ₁
And then, in the second base layer, when the length of the grating in the plane direction of the substantially parallel crystal faces to the non-magnetic substrate and L _2, and most preferably in the relation of L ₁ ≦ L _2.
Further, the difference [Delta] L of the grating length _{L 2} of the second base layer to the grating length _{L 1} of the first base _{layer, ΔL = (L 2 -L 1} ) / L 1
It is preferable that ΔL ≦ 15%.

The third underlayer 11 is made of nonmagnetic h. c. p.
It can be formed of a system material. For example, the third underlayer 11 is made of a single element of Ru or Ti, or a binary alloy containing Co as a main component and Cr or Ru added as a second element, or Ta, Pt, Pd added to the binary alloy. ,
Alloys to which at least one element is added among Ti, Y, Zr, Nb, Mo, W, and Hf can be used.

The thickness of the third underlayer 11 is generally 5 n
m to 25 nm. If the thickness of the third underlayer 11 is less than 5 nm, the intended effects of suppressing the initial growth of ferromagnetic particles and the lattice matching effect cannot be sufficiently achieved. On the other hand, when the thickness of the third underlayer 11 is more than 25 nm, the effect of suppressing the initial growth of ferromagnetic particles and the effect of lattice matching are saturated, which is only uneconomical.

The third underlayer 11 is formed by an ECR sputtering method,
The film can be formed by a C magnetron sputtering method or a vapor deposition method.

The crystal structure of the third underlayer 11 is preferably a hexagonal close-packed lattice (hcp). In particular, when the magnetic recording layer 13 is a thin film having an hcp crystal structure containing Co as a main component, if the magnetic recording layer 13 is directly formed on the second Distortion due to the difference in the crystal structure of the layer 13 is generated in the magnetic recording layer 13, and the crystal orientation of the magnetic recording layer 13 is deteriorated, and the characteristics are deteriorated. On the other hand, the crystal structure of the third underlayer 11 is h
If cp, the third underlayer 11 and the magnetic recording layer 13 have the same crystal structure, so that the magnetic recording layer 13 is hardly distorted, and the crystal distortion due to the second underlayer 9 is the third.
Of the magnetic recording layer 13
This is particularly preferable because effects such as prevention of deterioration in characteristics of the above are obtained. It is preferable that the magnetic recording layer 13 and the third underlayer 11 have an epitaxial growth relationship with each other.
Further, the magnetic recording layer 13 and the third underlayer 11 show almost the same crystal orientation, and moreover, the (11.0) plane or the (1
It is particularly preferable that the (0.0) plane is substantially parallel to the nonmagnetic substrate 3 for performing high-density recording.

Here, the magnetic recording layer 13 having the hcp crystal structure
A axis length at₁, C axis length is c ₁And the magnetic recording layer
A-axis of the third underlayer 11 of the hcp crystal structure immediately below
A₂, C axis length is c₂Then, a₁≧ a₂connection of
And c₁≧ c₂Preferably have a relationship
No. Also, the lattice of the magnetic recording layer 13 and the third underlayer 11
Length difference Δa = (a₁-A₂) / A₂, Δc = (c₁-C
₂) / C₂Δa ≦ 10%, Δc ≦ 10
%.

Further, the first underlayer 7 and the second underlayer 9
In (3), the (211) plane is preferentially oriented, and in the third underlayer 11 and the magnetic recording layer 13 disposed on the second underlayer 9, the (10.0) plane is preferentially oriented. Is preferred. Alternatively, when the (100) plane is preferentially oriented in each of the first underlayer 7 and the second underlayer 9, the third underlayer disposed on the second underlayer 9 In the underlayer 11 and the magnetic recording layer 13, the (11.0) plane is preferably preferentially oriented.

The total thickness of the first to third underlayers is preferably 50 nm or less. this is,
This film thickness is preferable from the viewpoint of controlling the crystal grain size and its distribution and also from the viewpoint of production.

The magnetic recording layer 13 for recording information is C
It is an alloy thin film mainly composed of o. More specifically, Co
Cr, Pt, Ta, Nb, Ti, Si, B, P, P
d, B, V, Tb, Gd, Sm, Nd, Dy, Eu, H
It is preferable to use a magnetic layer containing at least one or more elements selected from the group consisting of o, Ge, Mo and W. Needless to say, a plurality of elements may be included. For example, Co-Cr-Pt-T is used for the magnetic layer.
a system can be used, and Pd, Tb, G
d, Sm, Nd, Dy, Ho, and Eu can be used, and elements such as Nb, Si, B, and V can be used instead of Ta.

The magnetic recording layer 13 is preferably an in-plane film. If the magnetic recording layer 13 is an in-plane film, the magnetic recording layer 1
The c-axis of the magnetic particles constituting the magnetic particles 3, that is, the direction of the easy axis of magnetization is oriented in the in-plane direction. Increases, the magnetization in the recording bit can be stably maintained in the recorded direction.

In the Co-based magnetic layer, when Cr is added to Co, Cr is unevenly distributed in the magnetic layer. Further, by the blending of at least one element selected from the group consisting of Ti, Si, B, P, Ta and Nb, uneven distribution of Cr is further promoted by heat treatment during or after film formation. When treated at room temperature, Cr cannot be localized in the magnetic film. Further, it is preferable that the position where Cr is unevenly distributed precipitates (segregates) near or at the crystal grain boundary of the Co crystal particle. In the magnetic layer, C
o By distributing Cr in the vicinity of the crystal grain boundaries of crystal grains, the magnetic interaction between magnetic grains is reduced, and effects such as high-density recording and high-frequency recording (high-speed writing) can be obtained stably. Can be The magnetic recording layer 13 may have a single-layer structure or a laminated structure including a plurality of layers having different compositions.

Here, the concentration of Cr in the element group constituting the magnetic layer is defined as C (Cr) ₁ (unit: atomic%), and the element group constituting the second or third underlayer below the magnetic layer is Assuming that the concentration of occupied Cr is C (Cr) ₂ (unit: atomic%), it is preferable to have a relationship of C (Cr) ₁ <C (Cr) ₂ .

Further, the concentration of Pt in the group of elements constituting the magnetic recording layer 13 is defined as C (Pt) ₁ (unit: atomic%), and Pt occupying in the group of elements constituting the third underlayer under the magnetic layer is defined as C (Pt) _1. Is C (Pt) ₂ (unit: atomic%), it is preferable that C (Pt) ₁ ≧ C (Pt) ₂ .

As a method for forming the magnetic recording layer 13,
It is preferable to use the CR sputtering method. By using this film forming method, the effect of particularly strongly orienting the crystal orientation of the thin film to a certain direction is significantly larger than that of other film forming methods. Here, it is preferable from the viewpoint of film formation that the energy of the particles is controlled to be constant by the applied bias used to control the particles excited by the ECR sputtering method to a constant energy. Here, it is most preferable to use a DC power supply (DC) or a high-frequency power supply (RF) as a bias source to be applied.

The thickness of the magnetic recording layer 13 is generally 2 nm.
It is in the range of １５15 nm. If the thickness is less than 2 nm, it is difficult to form a uniform magnetic film. On the other hand, when the film thickness is 1
If the thickness exceeds 5 nm, high-density recording or high-frequency recording (high-speed writing) is performed because the magnetic crystal grains become coarse, the size distribution of the magnetic crystal particles increases, and the magnetic field from the magnetic head cannot be effectively applied to the entire magnetic film. This is not preferable because inconveniences such as not being able to perform are generated. Magnetic recording layer 13
Is most preferably in the range of 2 nm to 10 nm.

When the thickness of the magnetic recording layer 13 is large, the ferromagnetic particles of the magnetic recording layer 13 can be epitaxially grown on the second underlayer 9 without using the third underlayer 11. However, when the thickness of the magnetic recording layer 13 is small, it becomes difficult to epitaxially grow the ferromagnetic particles of the magnetic recording layer 13 on the second underlayer 9, and therefore, it is necessary to use the third underlayer 11. Nature occurs. However, from the viewpoint of reliably forming the magnetic recording layer 13 having the hcp crystal structure, regardless of the thickness of the magnetic recording layer 13, the third magnetic recording layer 13 having the hcp crystal structure may be used.
It is preferable to use the underlayer 11 described above.

The protective layer 1 in the magnetic recording medium 1 of the present invention
As 5, for example, a carbon protective film or the like can be suitably used. Needless to say, a protective film made of another material can be used. The carbon protective film is formed of, for example, sputter carbon, plasma CVD carbon, diamond-like carbon, hydrogen-containing carbon, oxygen-containing carbon, nitrogen-containing carbon, silicon-containing carbon, or the like. The carbon protective film has the effect of protecting the Co-based magnetic film and improving the slidability of the magnetic head.
However, if the carbon protective film alone is inferior in practical durability, a suitable lubricant (for example, a fluorine-based lubricant) can be applied to the upper surface of the carbon protective film to increase the durability of the carbon protective film.

The thickness of the protective layer 15 is generally 2 nm to 1 nm.
It is within the range of 0 nm. If the thickness is less than 2 nm, it is difficult to form a uniform protective layer. On the other hand, when the film thickness is 10 n
m, the distance between the magnetic head and the magnetic layer is large when reproducing recorded information, so that a sufficient magnetic flux cannot be detected by the magnetic head or when recording information, Since a sufficient magnetic field cannot be applied, the magnetic layer cannot be sufficiently magnetized, which causes disadvantages such as being unsuitable for high-density recording. Most preferably, the thickness of the protective layer 15 is in the range of 2 nm to 5 nm. The protective layer 15 is preferably formed by the ECR sputtering method. However, other deposition methods can be used if desired.

The non-magnetic substrate 3 in the magnetic recording medium 1 of the present invention is preferably a rigid substrate. Such non-magnetic substrates include, for example, glass, tempered glass, quartz,
Ceramic, metals (for example, aluminum, anodized aluminum, aluminum alloy, brass), silicon single crystal plate, surface thermal oxidation treated silicon single crystal plate or synthetic resins (for example, polyimide, polyester, polyethylene terephthalate, acrylic resin) It is composed of All such materials are known to those skilled in the art. The thickness itself of the nonmagnetic substrate 3 in the magnetic recording medium 1 of the present invention can be appropriately selected according to the application.

As a form of the magnetic recording medium 1 of the present invention,
Magnetic tapes and magnetic disks based on synthetic resin films such as polyester films and polyimide films,
It includes various forms of a structure that is in sliding contact with a magnetic head, such as a magnetic disk or a magnetic drum having a base made of a disk or a drum made of a synthetic resin film, an aluminum plate, a glass plate or the like.

[0044]

The magnetic recording medium of the present invention will now be specifically illustrated by way of examples. Example 1 A magnetic disk having the cross-sectional structure shown in FIG. 1 was manufactured. In this embodiment, the nonmagnetic layer 5 is made of Co—Cr—R
u-based thin film is used, and N
i-Al is used, and C is used as a material for forming the second underlayer 9.
r-Ti was used, and Co-Cr-Ru was used as a material for forming the third underlayer 11. Also,
A Co—Cr—Pt-based magnetic thin film was used as the magnetic recording layer 13, and a carbon (C) thin film was used as the protective film 15.

First, a glass substrate having a diameter of 2.5 inches was used as the nonmagnetic substrate 3 for a magnetic disk. The substrate used here is merely an example, and any size disk substrate may be used, or any material such as a metal substrate such as Al or an Al alloy or a resin substrate may be used.
It goes without saying that the effect of the present invention does not depend on the material and size of the substrate used. Also, glass, A
l or Al alloy substrate by plating or sputtering
Needless to say, a substrate on which an iP layer is formed may be used.

Next, a thin film made of Co ₅₅ Cr ₂₅ Ru ₂₀ was formed as a nonmagnetic layer 5 on a 2.5-inch glass substrate by DC magnetron sputtering. The film thickness was 5 nm. Co-Cr-
Ru was used, and Ar was used as a discharge gas. The gas pressure was 5 mTorr, the input power was 1 kW / 126 mmφ, and the substrate temperature during film formation was room temperature. This non-magnetic layer 5 was completely non-magnetic, and it was confirmed by X-ray diffraction that the crystal structure was an hcp structure.

On this non-magnetic layer 5, a Ni—Al alloy layer is applied as a first underlayer 7 by microwave (2.38 GHz).
It was formed by an ECR sputtering method using. The film thickness is 25
nm. The role of this layer is to control the crystal grain size of the magnetic recording layer 13, its distribution, and the orientation. Ni ₅₅ Al ₄₅ was used as a target, and Ar gas was used as a discharge gas. The pressure during sputtering is 0.3 mTorr
r, the input microwave power was 0.7 kW, and the substrate temperature was room temperature. An RF bias of 500 W was applied to draw in plasma excited by microwaves.
According to X-ray diffraction, the structure of the obtained film was a B2 structure, and the (211) plane was preferentially oriented. Here, the Ni ₅₅ Al ₄₅ alloy is used, but the composition is not absolute and can be changed depending on the material and composition of the magnetic layer used. Also, here, Ni-A
All of the l layers were prepared by ECR sputtering, but crystal nuclei at the initial stage of film formation were prepared by ECR sputtering, and DC
The film may be formed into a crystal grain of a certain size by a sputtering method. For these, a film formation method may be selected depending on the crystal grain size to be obtained. This is because the use of the ECR sputtering method can provide a film having highly oriented and fine crystal grains. The thickness of the first underlayer is:
Here, the value is 25 nm, but this value can be appropriately increased or decreased according to the material composition and the size of the crystal grains to be obtained.

When the lattice image of the interface between the nonmagnetic layer 5 and the first underlayer 7 was observed with a high-resolution TEM, the connection of the lattice was observed in some places although the epitaxial growth was not complete. Co-Cr- as 5
It was confirmed that the Ru film was a nucleus for crystal growth such as an underlayer formed thereon. This crystal growth nucleus effect was highest when the crystal structure of the nonmagnetic layer 5 was the hcp structure. The crystal structure of the nonmagnetic layer 5 has a bcc structure or bc
When a material having a lattice constant close to the lattice constant of the first underlayer 7 is used in the t structure, the crystal growth nucleus effect can be obtained to some extent, but is smaller than that in the hcp structure.

Next, Cr ₈₅ T was used as the second underlayer 9.
The i ₁₅ film was formed by DC magnetron sputtering. A Cr-Ti alloy was used as a target, and Ar was used as a discharge gas. Here, the alloy composition can be changed depending on the composition of the magnetic film and the material used. This is because the lattice spacing differs depending on the composition and material of the material. The pressure during sputtering was 2 mTorr, the input power was 1 kW, and the substrate temperature was 350 ° C. The thickness of the formed film was 15 nm. This film has a role of controlling orientation and lattice matching with the magnetic film. Further, it was clarified by X-ray diffraction and structural analysis by observation with a high-resolution transmission electron microscope that the second underlayer had a relationship of epitaxial growth with the first underlayer. In addition, although the DC magnetron sputtering method was used for manufacturing this film, it goes without saying that the ECR sputtering method using the resonance absorption of microwaves may be used. When this method is used, epitaxial growth is likely to occur, and the orientation can be controlled with high accuracy.

Subsequently, as the third underlayer 11, Co
_{A 55} Cr ₂₅ Ru ₂₀ alloy thin film was formed to a thickness of 5 nm. The technique used for the film formation was a DC magnetron sputtering method. Here, it goes without saying that the ECR sputtering method may be used for the film formation. When this method is used, controllability of particle diameter, distribution, and orientation can be greatly improved. A Co—Cr—Ru alloy was used as a target, and Ar was used as a discharge gas. Here, the alloy composition is
It can be changed depending on the composition of the magnetic film and the material used. This is because the lattice spacing differs depending on the composition and material of the material. The pressure during sputtering is 2 mTorr
r, the input power was 1 kW, and the substrate temperature was 350 ° C.
The third underlayer is to achieve lattice matching with the magnetic layer,
In addition, it has the effect of suppressing the initial growth of the magnetic layer.
Here, there is an epitaxial growth relationship between the second underlayer and the third underlayer, and the lattice length is Cr.
-Ti is 0.4330 nm, and Co-Cr-Ru is 0.1.
4763 nm. Cr-Ti has a bcc structure, Co-
Cr-Ru has an hcp structure and cannot be expressed by the length of the crystal axis, so that it is expressed by the lattice length. The calculated lattice length ratio was 12.5%. Here, the Co—Cr—Ru film as the third underlayer has an hcp structure, the a-axis length is 0.275 nm, and the c-axis length is 0.435 nm.
Met. When the length ratio of the lattice exceeded 15%, a good epitaxial relationship could not be obtained.

Next, a Co ₆₆ Cr ₁₈ Pt ₁₃ Ta ₃ film was formed as a magnetic recording layer 13 for information recording by DC sputtering. Here, comparing the Cr concentrations of the magnetic layer and the third underlayer, the underlayer was higher. Thereby, C in the Co—Cr—Pt—Ta-based magnetic film is
The segregation of r is promoted, and the magnetic interaction between the magnetic particles can be reduced. A Co—Cr—Pt—Ta alloy was used for the target, and pure Ar was used for the discharge gas. The pressure during sputtering is 3 mTorr, and the input DC power is 1 kW / 12
5 mmφ, the substrate temperature was 300 ° C. The thickness of the magnetic recording layer 13 for information recording was 10 nm. here,
The DC magnetron sputtering method was used for the film formation method.
It goes without saying that the R sputtering method may be used. E
When the CR sputtering method is used, the coercive force is increased by about 0.5 kOe as compared with the case where the DC magnetron sputtering method is used, and the coercive force is not deteriorated even at a film thickness of about 6 to 8 nm. In addition, the magnetic anisotropy greatly increased more than twice. Here, the Co—Cr—Pt—Ta film has an hcp structure, the a-axis length is 0.255 nm, and the c-axis length is 0.415 n
m. These values were compared with those of the third underlayer.
As a result, it was 7% for the a-axis and 5% for the c-axis. According to experiments, these differences were 1
If it exceeds 0%, lattice defects increase, and a good epitaxial relationship is not formed.

Finally, a carbon (C) film having a thickness of 3 nm was formed as the protective layer 15. ECR sputtering using microwaves was used for film formation. The pressure during sputtering is 0.5 mTorr, and the input microwave power is 0.6 k
W. Further, an RF bias voltage of 500 W was applied to draw in plasma excited by microwaves. As for the characteristics of the obtained C film, the hardness was 20 GPa or more, and according to Raman spectroscopy, it was found that the C film had sp3 binding properties. Although Ar is used as the sputtering gas here, it goes without saying that the film may be formed using a gas containing nitrogen. When a gas containing nitrogen is used, the particles become finer, and the obtained C film becomes denser, so that the protection performance can be further improved. Since the structure of this film greatly depends on the conditions of sputtering, these conditions are not absolute. Here, the reason why the ECR sputtering method is used for the production of the protective film is that even a very thin film having a thickness of 2 to 3 nm is dense, pinhole-free, and has good coverage.
This is because a film is obtained. This is done by RF sputtering or D
This is a remarkable difference as compared with the C sputtering method. In addition to this, there is a feature that damage to the magnetic film when forming the protective film is extremely small. In particular, when high-density recording exceeding 50 Gb / in ² is performed, the magnetic film thickness can be reduced to 10 nm or less, so that the influence of damage to the magnetic film during film formation becomes more remarkable. In such a case,
The ECR sputtering method is a very effective film forming method, and is effective when a magnetic film for ultra-high density magnetic recording is manufactured.

FIG. 2 shows the crystal structures of the first underlayer to the magnetic recording layer in the magnetic disk manufactured as described above. As is apparent from this figure, the second underlayer 9 having the same crystal structure as the first underlayer 7 is epitaxially grown, and the lattice spacing substantially equal to the lattice spacing of the second underlayer 9 is set. The third underlying layer 11 having the hcp structure is epitaxially grown, and the magnetic recording layer 13 having the same hcp crystal structure is epitaxially grown.

Further, the structure and the structure of the magnetic disk manufactured as described above were analyzed. First, the surface and cross section were observed by TEM, and the structure and structure of the magnetic disk were analyzed. First, when the crystal particle size was determined, the particles present in a square of 200 nm were examined, and the average particle diameter was 10 nm. The particle size distribution in this system was a normal distribution, and the standard deviation was 0.5 nm in terms of σ, which was 5% of the particle diameter.
Without using a Ni-Al first underlayer produced by ECR sputtering, Cr-Ti, Co-Cr-Ru, Co-Cr-Pt-
When the structure of the medium in which the Ta and C films were sequentially laminated was observed, the average particle size was 15 nm, and the standard deviation was 1.5 n.
m. As described above, when the Ni—Al film formed by the ECR sputtering method of the present invention was used, the crystal grain size was reduced, and the distribution thereof could be reduced. Further, when the cross-sectional structure of this medium was observed by TEM, it was found that epitaxial growth was excellent from the three underlayers to the magnetic recording layer.

Next, the structure of the magnetic recording medium was analyzed by an X-ray diffraction method. A diffraction peak of (112) of Ni-Al was observed around 2θ = 80 °. In addition, 2θ
= A diffraction peak was observed around 41 °. Considering the TEM observation results, the peak around 2θ = 41 ° is C
o-Cr-Pt-Ta (10.0) diffraction peak,
It can be seen that the Co—Cr—Pt—Ta magnetic particles forming the magnetic layer 9 are strongly oriented. This orientation is suitable for high-density magnetic recording. Here, when the magnetic layer is manufactured by the ECR sputtering method, the peak near 2θ = 41 ° has a DC
It is stronger than when made by sputtering, and
Since the half width of the peak was also narrowed, it was found that the crystallinity of the magnetic layer was improved. As described above, by combining the film formation method using the resonance absorption method such as the ECR sputtering and the underlayer whose functions are separated, the crystallinity of the magnetic layer can be greatly improved. As a result, the coercive force and anisotropy were increased, and heat resistance such as thermal fluctuation and thermal demagnetization was improved.

Next, the magnetic characteristics of the magnetic recording medium were measured. The obtained magnetic properties show that the coercive force is 3.5 kOe and I
sv is 2.5 × 10 ⁻¹⁶ emu, S which is an index of the squareness of the hysteresis in the MH loop is 0.86, S
^† was 0.91 and the film had good squareness. As described above, the index indicating the squareness is large (ie, close to the square) because the hcp underlayer (third underlayer) having a higher Cr concentration than the magnetic recording layer is used. In C
This is because the interaction between magnetic crystal grains is reduced because r is promoted to segregate at crystal grain boundaries. This point was confirmed by μ Auger analysis.

Next, a lubricant was applied to the surface of a magnetic disk using a magnetic recording medium having such magnetic characteristics, and the recording / reproducing characteristics of the disk were evaluated. FIG. 4 schematically shows the configuration of the magnetic disk drive. As the magnetic head 23, a thin film magnetic head using a soft magnetic film having a high saturation magnetic flux density of 2.1 T is used for recording, and
A dual spin valve type magnetic head having a giant magnetoresistance effect was used. The magnetic head is controlled by a drive system 24. The magnetic disk 21 was rotated by the spindle 22, and the distance between the head surface and the magnetic recording layer was kept at 12 nm. A signal corresponding to 50 Gb / in ² was recorded on the disk 21 and the S / N of the disk was evaluated.
A reproduction output of dB was obtained. Here, in the case of the control medium having no nonmagnetic layer 5, the noise was increased by 2 dB, the signal level was decreased by 1 dB, and the total was decreased by 3 dB. From these results, it can be understood that the provision of the nonmagnetic layer 5 can improve the S / N ratio of the magnetic recording medium.

When the magnetization reversal unit was measured by a magnetic force microscope (MFM), it was found to be about 3 particles from 2 and sufficiently small. At the same time, the zigzag pattern existing in the magnetization transition region was significantly smaller than that of the conventional medium. In addition, thermal fluctuation and demagnetization due to heat did not occur. This is because the distribution of the crystal grain size of the magnetic film is small. When the defect rate of this disk was measured, it was 1 × 10 ⁻⁵ or less as a value when no signal processing was performed.

Example 2 A magnetic disk having a magnetic recording layer having a two-layer structure in which a second magnetic recording film having a different composition from the first magnetic recording film was laminated was manufactured. A Co ₆₆ Cr ₁₈ Pt ₁₃ Ta ₃ film is formed as a first magnetic recording film to a thickness of 8 nm by a DC magnetron sputtering method on the same third underlayer as that used in the magnetic disk of Example 1. did. Subsequently, Co ₆₈ Cr ₁₉ P is used as a second magnetic recording film.
The t ₁₃ film was formed to a thickness of 8nm by DC magnetron sputtering. The first magnetic recording film and the second magnetic recording film were epitaxially grown continuously from the third underlayer.

In this case, the concentration of Pt is the first and the second.
Were the same in both magnetic recording films. The Pt concentration is a value appropriately selected in consideration of factors such as anisotropy and noise control. According to experiments performed by the present inventors, the Pt concentration of the second magnetic recording film is determined by the first magnetic recording film. It has been found that it is preferable to set the value equal to or lower than the recording film.

Next, the magnetic characteristics of the two-layer magnetic recording layer were measured. The obtained magnetic properties show that the coercive force is 3.2 kO
e, Isv is 2.5 × 10 ⁻¹⁶ emu, and S, which is an index of the squareness of the hysteresis in the MH loop, is 0.8.
5, S ^† was 0.90 and had good magnetic properties. Next, a lubricant was applied to the medium surface of the magnetic disk using the two-layered magnetic recording layer having such magnetic characteristics, and the recording / reproducing characteristics of the disk were evaluated. The configuration of the magnetic disk device used was the same as that of the first embodiment. The distance between the head surface and the two-layer magnetic recording layer was kept at 15 nm. When a signal corresponding to 50 Gb / in ² was recorded on this disk and the S / N of the disk was evaluated, 32 dB was obtained.
Was obtained. Here, a magnetic force microscope (MF)
When the magnetization reversal unit was measured by M), it was found to be about 3 particles from 2 and sufficiently small. At the same time, the zigzag pattern existing in the magnetization transition region was significantly smaller than that of the conventional medium. In addition, thermal fluctuation and demagnetization due to heat did not occur. This is because the distribution of the crystal grain size of each magnetic recording film is small.
When the defect rate of this disk was measured, it was 1 × 10 ⁻⁵ or less as a value when no signal processing was performed.

For evaluation of thermal stability, 300 k
A signal was recorded on the medium of Example 1 and the medium of Example 2 at the recording density by FCI, and the time dependency of the output change of the recorded signal was examined. As a result, in the medium of the first embodiment, the output of the reproduced signal is about 1.0 after 100 hours from the recording.
In contrast to about 0%, the medium of Example 2 was about 0.1%.
It was found that the thermal stability of the recording bit was good with a reduction of about 8%. This is considered to be because the thermal stability of the magnetic particles was improved by laminating a magnetic layer having a large magnetic anisotropy on the upper side as compared with the lower magnetic layer.

Embodiment 3 Next, a description will be given of an example of forming a magnetic disk using a Cr film formed by ECR sputtering as the first underlayer 7 in the magnetic recording medium 1 having the laminated structure shown in FIG.

A glass substrate having a diameter of 2.5 inches was used as the nonmagnetic substrate 3. Example 1 A non-magnetic layer 5 was formed on a glass substrate.
The film was formed under the same processing conditions as described in (1). The crystal structure of the nonmagnetic layer 5 was an hcp structure.

On this nonmagnetic layer 5, a Cr layer was formed as a first underlayer 7 by using a microwave (2.38 GHz).
It was formed by CR sputtering. The pressure during sputtering is 0.5 mTorr, the input microwave power is 0.5 kW,
The substrate temperature was room temperature. Further, an RF bias voltage of 500 V was applied to draw in plasma excited by microwaves. Here, the bias is not limited to RF, and a DC bias can be used because the bias is a metal target. However, from the viewpoint of controlling the orientation and the crystal grains, the RF bias is more preferable. Ar was used as a discharge gas, and pure Cr was used as a target. Cr formed
The thickness of the film was 25 nm. On top of this, a Cr—Ti film (second underlayer 9), a Co—Cr—Ru film (third underlayer 11), a Co—Cr—Pt—Ta film (magnetic recording layer 1)
3) and a C film (protective layer 15) were sequentially laminated. The film forming method of these films was the same as the film forming method described in Example 1.

As a result of examining the crystal structures of the first underlayer to the magnetic layer of the obtained magnetic disk by the X-ray diffraction method, as shown in FIG. 3, the magnetic recording layer was formed of Co-Cr-Pt-Ta ( 11.0) Diffraction peaks were observed in the first and second underlayers as the main diffraction peaks of Cr and Cr-Ti from (200). In addition, since the peak position from the second underlayer was observed on the lower angle side compared to the peak position of the first underlayer, both showed the same crystal orientation, and the second underlayer had a higher crystal lattice. Is larger. FIG. 5 shows the analysis results. As shown, the crystal structure of the first underlayer 7 is bcc and Cr
Was strongly oriented. Further, a second underlayer 9 having a crystal structure substantially the same as the crystal structure of the first underlayer 7 is epitaxially grown, and a third hcp structure having the same lattice spacing as that of the second underlayer 9 is formed. Underlayer 11 was epitaxially grown. Co—Cr—Ru of the third underlayer 11 of the hcp structure and C of the magnetic recording layer 13 of the hcp structure
In each of the o-Cr-Pt-Ta, the (11.0) plane was strongly oriented.

From the observation of the medium surface by TEM, the average particle diameter of the magnetic layer was 10 nm, which was almost the same as the value of the underlayer. When the particle size distribution of these particles was determined, it was 0.7 nm in σ. Thus, it can be seen that the crystal grains of the magnetic layer are fine and the particle size distribution is small. In addition, from the cross-sectional observation, it was found that the underlayer and the magnetic layer were epitaxially grown. The structure was a good columnar structure growing vertically from the substrate, and the crystal grain size did not change from the substrate surface to the medium surface. Therefore, the Cr underlayer is effective in controlling the size and distribution of the crystal grains, and further, the crystal orientation. If the Cr underlayer is used, a film having a bcc structure can be obtained.
For Cr, the same effect can be obtained with the same film thickness as the Ni-Al alloy base layer.

The magnetic characteristics of the magnetic recording layer were measured. The obtained magnetic properties are as follows: coercive force is 3.5 kOe, Isv is 3
× 10 ⁻¹⁶ emu, S, which is an index of the squareness of the hysteresis in the MH loop, is 0.85 and S ^† is 0.90.
And had good magnetic properties.

Next, a lubricant was applied to the medium surface of a magnetic disk having a magnetic recording layer having such magnetic characteristics, and the recording / reproducing characteristics of the disk were evaluated. The same magnetic disk device as that used in Example 1 was used.
The distance between the head surface and the magnetic recording layer was kept at 15 nm. When a signal corresponding to 50 GB / in ² was recorded on this disk and the S / N of the disk was evaluated, a reproduced output of 32 dB was obtained. Here, when the magnetization reversal unit was measured by a magnetic force microscope (MFM), it was found that the number was about three particles from the particle 2, which was sufficiently small. At the same time, the zigzag pattern existing in the magnetization transition region was significantly smaller than that of the conventional medium. In addition, thermal fluctuation and demagnetization due to heat did not occur. This is because the distribution of the crystal grain size of the magnetic recording layer is small. When the defect rate of this disk was measured, it was 1 × 10 ⁻⁵ or less as a value when no signal processing was performed.

[0070]

As described above, according to the present invention,
A non-magnetic layer having a hcp structure is formed on a surface of a non-magnetic substrate, a plurality of underlayers having a specific crystal structure are provided on the non-magnetic layer, and a magnetic recording layer is epitaxially grown on the underlayer. Thereby, the crystal grain size in the magnetic recording layer is miniaturized, and the crystal orientation is improved, whereby the magnetic interaction between the magnetic particles is reduced, and the unit of magnetization reversal at the time of recording or erasing can be reduced. As a result, an ultra-high-density recording medium having an improved S / N ratio exceeding 50 Gb / in ² can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an example of a magnetic recording medium of the present invention.

FIG. 2 is a schematic diagram showing a crystal structure of a first underlayer to a magnetic layer of the magnetic disk manufactured in Example 1.

FIG. 3 shows the structure of the magnetic disk manufactured in Example 3 as X
It is a characteristic view showing the result analyzed by the line diffraction method.

FIG. 4 is an example of a magnetic disk device used for recording / reproducing the magnetic disks manufactured in Examples 1 to 3,
(A) is a plan view thereof, (B) is B in (A)
It is sectional drawing which followed the -B line.

FIG. 5 is a schematic diagram showing a crystal structure of a first underlayer to a magnetic layer of the magnetic disk manufactured in Example 3.

[Explanation of symbols]

 Reference Signs List 1 magnetic recording medium of the present invention 3 nonmagnetic substrate 5 nonmagnetic layer 7 first underlayer 9 second underlayer 11 third underlayer 13 magnetic recording layer 15 protective layer 21 magnetic disk 22 spindle 23 magnetic head 24 drive system

Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court II (Reference) H01F 10/30 H01F 10/30 41/18 41/18 (72) Inventor Satoru Matsunuma 1-1-1 Ushitora Ushitora, Ibaraki-shi, Osaka No. 88 Inside Hitachi Maxell Co., Ltd. (72) Inventor Tetsunori Kanda 1-1-88 Ushitora, Ibaraki City, Osaka Prefecture Inside Hitachi Maxell Co., Ltd. (72) Tetsuo Mizumura 1-1-88 Ushitora, Ibaraki City, Osaka Prefecture Hitachi Maxell Co., Ltd. (72) Inventor Teruaki Takeuchi 1-88 Ushitora, Ibaraki-shi, Osaka F-term within Hitachi Maxell Co., Ltd. 4K029 AA02 AA06 AA08 AA09 AA11 AA24 AA25 BA02 BA06 BA07 BA11 BA12 BA13 BA16 BA17 BA24 BA25 BC06 BD11 CA01 CA05 EA01 5D006 BB01 BB07 CA01 CA05 CA06 EA03 FA09 5D112 AA03 BD03 FA04 5E049 AA04 AA09 AC05 BA06 DB12 GC01

Claims (22)

[Claims] 1. A magnetic recording medium having a magnetic recording layer on a non-magnetic substrate, wherein a non-magnetic layer having a hcp crystal structure is formed on one surface of the non-magnetic substrate. First on top,
A magnetic recording medium, wherein a second and a third underlayer are formed in this order, and the magnetic recording layer is formed on the third underlayer. 2. The non-magnetic layer is formed of an alloy material mainly composed of Co and containing at least one element selected from the group consisting of Cr, Ru, Zr, Ta, Nb and V in Co. 2. The magnetic recording medium according to claim 1, wherein the magnetic recording medium has been recorded. 3. The nonmagnetic layer has a thickness of 2 to 20 nm.
The magnetic recording medium according to claim 1, wherein 4. The magnetic recording medium according to claim 1, wherein the first underlayer formed on the nonmagnetic layer is formed by an ECR sputtering method. 5. The magnetic recording medium according to claim 1, wherein the first underlayer has a B2 structure or a body-centered cubic (bcc) crystal structure. 6. The method according to claim 1, wherein the second underlayer is a body-centered square lattice (bc).
2. The magnetic recording medium according to claim 1, wherein the magnetic recording medium has a t) or bcc crystal structure, and the second underlayer is epitaxially grown on the first underlayer. 7. The first underlayer and the second underlayer have substantially the same crystal orientation, and the (211) plane or the (100) plane of the first underlayer and the second underlayer. 2. A surface according to claim 1, wherein said surface is substantially parallel to said non-magnetic substrate.
3. The magnetic recording medium according to claim 1. 8. The first underlayer, the length of the grating and L ₁ in the plane direction of the substantially parallel crystal faces to the non-magnetic substrate, the second base layer, for non-magnetic base when the L ₂ the length of the grating in the plane direction of the substantially parallel crystal faces Te, magnetic recording medium according to claim 7, characterized in that a relation of L ₁ ≦ L _2. 9. The difference ΔL between the lattice length L2 of the _second underlayer and the lattice length L1 of the _first underlayer is represented by ΔL = (L
8. The magnetic recording medium according to claim 7, wherein ΔL ≦ 15% when defined as ₂ −L ₁ ) / L ₁ . 10. The first underlayer is made of a Ni—Al binary alloy, or a ternary or more alloy containing Ni—Al as a main component, Cr alone and Cr as V, Mo, W, Nb, Ti. ,
The magnetic recording according to claim 5, wherein the magnetic recording is made of a material selected from the group consisting of alloys to which at least one element selected from the group consisting of Ta, Ru, Zr, and Hf is added. Medium. 11. The second underlayer is made of a binary alloy of Ni—Al or a ternary or more alloy containing Ni—Al as a main component, Cr alone and Cr with V, Mo, W, Nb, and Ti. ,
7. The magnetic recording according to claim 6, wherein the magnetic recording is made of a material selected from the group consisting of alloys to which at least one element selected from the group consisting of Ta, Ru, Zr, and Hf is added. Medium. 12. The magnetic recording medium according to claim 1, wherein the third underlayer has an hcp crystal structure. 13. The third underlayer is made of a single element of Ru or Ti, or Co as a main component and C as a second element.
r or Ru added binary alloy or Ta, Pt, Pd, Ti, Y, Zr, Nb, M
The magnetic recording medium according to claim 12, wherein the magnetic recording medium is formed of a material selected from the group consisting of alloys to which at least one element selected from the group consisting of o, W, and Hf is added. 14. The magnetic recording layer has Co as a main component and Cr, Pt, Ta, Nb, Ti, Si, B, P, P.
d, V, Tb, Gd, Sm, Nd, Dy, Eu, Ho,
2. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is formed from at least one element selected from the group consisting of Ge, Mo, and W. 15. The magnetic recording medium according to claim 14, wherein the magnetic recording layer has a hexagonal close-packed lattice (hcp) crystal structure containing Co as a main component. 16. The magnetic recording layer and the third underlayer have an epitaxial growth relationship with each other, and the magnetic layer and the third underlayer have substantially the same crystal orientation. 2. The magnetic recording medium according to claim 1, wherein the (10.0) plane or the (11.0) plane of the layer and the third underlayer is substantially parallel to the nonmagnetic substrate. 17. When the a-axis length of the magnetic recording layer is a ₁ , the c-axis length is c _1, and the a-axis length of the third underlayer is a ₂ , and the c-axis length is c ₂ , ₁ ≧ a ₂ relationship may, and magnetic recording medium according to claim 16, characterized in that there is a relation of c ₁ ≧ c _2. 18. The magnetic recording method according to claim 1, wherein the a-axis length of the magnetic recording layer is a ₁ , the c-axis length is c ₁ , the a-axis length of the third underlayer is a ₂ , and the c-axis length is c _2. Δa = (a ₁ −a ₂ ) / a ₂ , Δ, the difference in lattice length between the layer and the third underlayer
When defined by c = (c ₁ −c ₂ ) / c ₂ , Δa ≦ 10
17. The magnetic recording medium according to claim 16, wherein a relationship of% and Δc ≦ 10% is satisfied. 19. The first underlayer and the second underlayer are preferentially oriented in the (211) plane, and the third underlayer and the magnetic recording layer are preferentially oriented in the (10.0) plane. 2. The magnetic recording medium according to claim 1, wherein: 20. The (100) plane is preferentially oriented in the first underlayer and the second underlayer, and the (11.0) plane is preferentially oriented in the third underlayer and the magnetic recording layer. 2. The magnetic recording medium according to claim 1, wherein: 21. The concentration of Cr in an element group constituting the magnetic recording layer is C (Cr) ₁ (unit: atomic%),
C occupying in the group of elements constituting the second or third underlayer.
When the concentration of r is C (Cr) ₂ (unit: atomic%),
15. The magnetic recording medium according to claim 14, wherein a relationship of C (Cr) ₁ <C (Cr) _{2 is} satisfied. 22. A concentration of Pt in an element group constituting the magnetic recording layer is C (Pt) ₁ (unit: atomic%),
When the concentration of Pt in the element group constituting the third underlayer is C (Pt) ₂ (unit: atomic%), C (Pt)
The magnetic recording medium according to claim 14, wherein a relationship of t) ₁ ≧ C (Pt) _{2 is} satisfied.