JP2001110044A - Method of manufacturing rependicular magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a perpendicular magnetic recording medium capable of mass production and obtaining a high reproducing output and having a low medium noise. SOLUTION: This method consists at least of a film-forming stage for forming a multi-layered structure by film-forming a hard magnetic pinning layer, a soft magnetic base layer and a perpendicular magnetic recording layer on a non-magnetic substrate and a stage wherein the multi-layered structure is heat- treated in the state that a magnetic field is applied to the structure in a prescribed direction after the film-forming stage to arrange the magnetization of the soft magnetic base layer in a prescribed direction. Plural sheets of the perpendicular magnetic recording media 21a, 21b, 21c and 21d can be film-formed and heat-treated after film-forming suitably for mass production. The heat- treating temperature T and heat treating time τ are regulated by a specified relation, for example, in case of the perpendicular magnetic recording medium having three-layered structure, when the crystallization temperature of the soft magnetic base layer is expressed by Tc, the heat-treating time τ needs to satisfy the relational formula τ>=3.5 (Tc-T)/T.

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 such as a magnetic disk or a magnetic tape, and more particularly to a perpendicular magnetic recording medium having a two-layer structure in which a soft magnetic underlayer and a perpendicular magnetic recording layer are formed on a nonmagnetic substrate. The present invention relates to a recording medium and a three-layer perpendicular magnetic recording medium having a hard magnetic pinning layer added thereto.

[0002]

2. Description of the Related Art Perpendicular magnetic recording media have attracted attention because they can perform higher density recording than current in-plane recording. As a magnetic recording medium, a perpendicular magnetic recording medium having a two-layer structure including a soft magnetic underlayer and a perpendicular magnetic recording layer has been studied in addition to a single-layer film medium including a single perpendicular magnetic recording layer. In particular, when a perpendicular magnetic recording medium having a two-layer structure is combined with a single-pole type head, efficient recording and reproduction can be performed. Above all, a perpendicular magnetic recording medium having a two-layer structure using a Co-Zr-based amorphous soft magnetic film as an underlayer disclosed in Japanese Patent Application No. 3-278595 (hereinafter, referred to as "first prior art") is a perpendicular magnetic recording medium. Since a perpendicular magnetic recording layer with sharp orientation can be obtained, it is particularly effective for improving the recording efficiency.

However, in the magnetic recording medium disclosed in the first prior art, in particular, a disk-shaped magnetic recording medium, the signal intensity is attenuated with time only by rotating the magnetic recording medium after recording the signal. Cause the problem.
This is because, when the magnetic recording medium rotates, the magnetization of the soft magnetic underlayer composed of the Co-Zr-based amorphous soft magnetic film is easily reversed due to the influence of an external magnetic field such as terrestrial magnetism. This occurs because the recording signal of the perpendicular magnetic recording layer is erased due to the generated domain wall movement. The magnetic field generated from the movement of the domain wall of the soft magnetic underlayer also causes a problem of increasing medium noise.

Accordingly, the inventors have disclosed in Japanese Patent Laid-Open No. 7-12994.
In Japanese Patent Publication No. 6 (hereinafter referred to as "second prior art"), by providing an in-plane oriented hard magnetic pinning layer having a residual magnetization in the radial direction between a substrate and a soft magnetic underlayer, recording and reproducing characteristics are improved. A method for preventing the demagnetization due to the rotation of the magnetic recording medium and reducing the medium noise without damaging the magnetic recording medium has been previously proposed. The in-plane oriented hard magnetic pinning layer is Co-
When the disk-shaped magnetic recording medium having Sm has uniaxial magnetic anisotropy in the radial direction, a particularly large effect can be obtained. Further, as a technique for increasing the magnetic permeability μ of the soft magnetic underlayer to increase the reproduction output, as shown in the second prior art, the hard magnetic pinning layer and the soft magnetic pinning layer are formed in a vacuum of 10 ⁻³ Pa or less after film formation. 24k strong enough to saturate the magnetization of the magnetic underlayer
A method of performing heat treatment in a rotating magnetic field of A / m is effective. This utilizes the fact that atoms in the Co—Zr-based amorphous soft magnetic film are diffused by the action of heat and a magnetic field, and the magnetic permeability μ is increased by weakening the anisotropic magnetic field.

[0005]

As described above, a perpendicular magnetic recording medium having a three-layer structure has been proposed in order to improve the disadvantages of a perpendicular magnetic recording medium having a two-layer structure. A method for obtaining a high reproduction output has been sought. However, there is no known technique for obtaining a high reproduction output with a small medium noise while keeping the perpendicular magnetic recording medium of the two-layer structure.

On the other hand, in a perpendicular magnetic recording medium having a three-layer structure, as shown in the second prior art, a DC magnetron sputtering apparatus having a special structure as shown in FIG. The soft magnetic underlayer is formed by sputtering while applying a magnetic field to the soft magnetic underlayer, so that the axis of easy magnetization of the soft magnetic underlayer is aligned in the radial direction of the substrate after the film is formed. In FIG. 9, the rare earth permanent magnet 4 configured to form a magnetic field near the target 43 is shown.
The structure is such that the magnetic field from 1, 42 is applied to the substrate 11. When the substrates 11 for research and development are formed one by one, an apparatus configuration as shown in FIG. 9 is possible. However, when considering mass production, in particular, in a mass production method of a type in which a film is formed on a plurality of substrates at once by a sputtering apparatus having a pallet-type substrate holder, the structure of the apparatus is
It is difficult to mount a function of applying a magnetic field in the radial direction of each substrate during film formation. Even if a sputtering apparatus for mass production is equipped with a function and a mechanism for applying a magnetic field to each of the substrates in the radial direction during film formation, the apparatus becomes complicated, and enormous equipment investment and running cost are reduced. Invite a rise.

After all, a sputtering apparatus that can be used for the method of manufacturing a magnetic recording medium described in the second prior art is
The range of use is limited to a relatively small film forming apparatus or the like, which is disadvantageous for mass production. Therefore, the method for manufacturing a magnetic recording medium described in the second prior art can be said to be a technique that leads to a high production cost.

Further, as the density is increased, it is necessary to unnecessarily improve the magnetic permeability μ of the soft magnetic underlayer at around 1 MHz as shown in the second prior art, which deteriorates the characteristics in a high frequency region of 10 MHz or more. Tends to be rather harmful.

The present invention has been made in view of the above points, and has as its object to provide a method of manufacturing a perpendicular magnetic recording medium having a two-layer structure capable of obtaining high reproduction output with small medium noise.

Another object of the present invention is to use a film forming apparatus for mass production, which is capable of obtaining a high reproduction output with a small medium noise, and having a three-layer vertical structure having a high stability of a recording signal. An object of the present invention is to provide a method for manufacturing a perpendicular magnetic recording medium capable of mass-producing a magnetic recording medium.

Still another object of the present invention is to provide a method of manufacturing a perpendicular magnetic recording medium capable of obtaining a high magnetic permeability μ in a high frequency range of several tens of MHz or more.

Still another object of the present invention is to provide a high-performance and high-quality perpendicular magnetic recording medium inexpensively and in large quantities.

[0013]

In order to achieve the above object, a method for manufacturing a perpendicular magnetic recording medium according to the first aspect of the present invention comprises the steps of (a) forming a perpendicular magnetic recording layer and a soft magnetic layer on a non-magnetic substrate. Forming a multilayer structure by forming an underlayer and (b)
After the formation of the multilayer structure, the multilayer structure is subjected to a heat treatment at a heat treatment temperature T (unit: absolute temperature) and a heat treatment time τ (unit: time) in a state in which a magnetic field H is applied in a predetermined direction, to thereby form a soft magnetic underlayer. Aligning the magnetization in a predetermined direction. Further, in the method for manufacturing the perpendicular magnetic recording medium according to the first aspect of the present invention, the heat treatment time τ of the heat treatment performed after the formation of the multilayer structure is such that C ₁ is the material of the soft magnetic underlayer and the magnetic recording medium. A constant determined by the structure, τ ≧ C, where Tc (unit: absolute temperature) is the crystallization temperature of the soft magnetic underlayer.
₁ is the time that satisfies the relationship of (Tc-T) / T. Here, "perpendicular magnetic recording medium" refers to a magnetic disk,
A magnetic tape may be used. The "predetermined direction" in the first aspect of the present invention refers to the direction perpendicular to the direction of the magnetic flux on the medium surface created by the head of the magnetic recording / reproducing apparatus, that is, it must be the circumferential direction. That is, generally, in the case of a magnetic disk, it is in the radial direction of the magnetic disk, and in the case of a magnetic tape, generally in the width direction of the magnetic tape. The magnetic field H at the time of the heat treatment has such a magnitude that the soft magnetic underlayer saturates on the hard axis. The atmosphere during the heat treatment may be in a vacuum or an inert gas.

When the soft magnetic film is heat-treated under the application of a magnetic field H of a predetermined direction and strength, the change of the domain wall due to the movement of atoms due to the action of heat and a magnetic field is expressed by the following equation (1). It is thought to change in a natural logarithmic manner. That is, when the magnetic field H is applied in a predetermined direction, the change in the anisotropic magnetic field Hk (t) at the time t with the direction as the easy axis of magnetization is expressed as Hk (t) = Hk (0) · {1- 2exp (-at)}... (1) Here, Hk (0) is the anisotropic magnetic field of the soft magnetic underlayer before the heat treatment (t = 0).
A is a constant indicating the degree of time change of the anisotropic magnetic field Hk (t), and as a function of the heat treatment temperature T (absolute temperature), a = K · T / (Tc−T) (2) is indicated. Here, K is a constant determined by the structure of the magnetic recording medium and its material, and can be obtained by an experiment (empirical rule). For example, when the Co—Zr-based amorphous soft magnetic film is used as a soft magnetic underlayer, K = 0.140 in the case of a perpendicular magnetic recording medium having a two-layer structure according to experimental results of the present inventors described later. Taking close values has been obtained as new knowledge.

On the other hand, if equation (1) is used, the anisotropic magnetic field H
The heat treatment time τ at which k (t) = 0 is obtained by the following equation (3).

Τ = −log (1/2) /a≒0.7/a (3) Therefore, it can be obtained as a new finding by the experiment of the present inventor.
K value (for example, Co-Zr-based amorphous soft magnetic film
Is K = 0.140. ) For equation (2)
The constant a obtained from the equation (2) is used for the equation (3).
In the heat treatment of the heat treatment performed after the formation of the multilayer structure,
The relationship between the heat treatment temperature T and the shortest heat treatment time τ is determined.
You. That is, the perpendicular magnetic recording medium according to the first feature of the present invention.
In the body manufacturing method, τ ≧ C₁(Tc-T) / T
Heat treatment with a heat treatment time τ that satisfies the relationship
Irrespective of the direction of the axis of easy magnetization immediately after film formation,
Align magnetization and easy axis of magnetization in the direction of applied magnetic field H
It is possible. For example, a Co-Zr-based amorphous
When the soft magnetic film is a soft magnetic underlayer, C ₁
= 5, which satisfies the relationship τ ≧ 5 (Tc−T) / T
The heat treatment may be performed for a heat treatment time τ.

As a result, even in the case of a perpendicular magnetic recording medium having a two-layer structure, a magnetic recording medium having small medium noise with respect to an externally applied magnetic field can be obtained by heat treatment in a magnetic field after film formation.
Further, since heat treatment in a magnetic field after film formation can be performed by a heat treatment apparatus having a simple structure, heat treatment can be performed in a large amount at a time, which is suitable for mass production.

According to a second aspect of the present invention, there is provided a method for manufacturing a perpendicular magnetic recording medium, comprising the steps of (a) forming a hard magnetic pinning layer, a soft magnetic underlayer, and a perpendicular magnetic recording layer on a non-magnetic substrate; Step of forming a structure, and (b) after forming the multilayer structure, heat treatment temperature T (unit: absolute temperature) and heat treatment time τ (unit:
Time) to align the magnetization of the soft magnetic underlayer in a predetermined direction. Further, in the method for manufacturing a perpendicular magnetic recording medium according to the second aspect of the present invention, the heat treatment time τ of the heat treatment performed after the formation of the multilayer structure is such that C ₂ is the material of the soft magnetic underlayer and the magnetic recording medium. Τ ≧ C ₂ (Tc−T) /, where Tc (unit: absolute temperature) is a constant determined by the structure of
It is time to satisfy the relationship T. Similarly to the first feature, the “perpendicular magnetic recording medium” may be a magnetic disk or a magnetic tape. The "predetermined direction" refers to a direction perpendicular to the direction of the magnetic flux on the medium surface created by the head of the magnetic recording / reproducing apparatus, that is, it must be the circumferential direction. The magnetic field H at the time of the heat treatment has such a magnitude that the soft magnetic underlayer saturates on the hard axis. The atmosphere during the heat treatment may be in a vacuum or an inert gas.

As described in the first aspect of the present invention, when the soft magnetic film is heat-treated in a predetermined direction under the application of a magnetic field H having a predetermined intensity, the action of heat and a magnetic field causes the atomic force of atoms. The change of the domain wall due to the movement is expressed by the equation (1), and the constant a indicating the degree of the time change of the anisotropic magnetic field Hk (t) is
It is shown by equation (2). Then, a constant K determined by the structure and the material of the magnetic recording medium that defines the equation (2)
Is determined as a function of the material of the soft magnetic underlayer according to the experimental results of the present inventors. In the case of the Co—Zr-based amorphous soft magnetic underlayer / hard magnetic pinning layer, a value close to K = 0.20 is obtained. Take. Since the heat treatment time τ at which the anisotropic magnetic field Hk (t) = 0 is obtained by the equation (3), using the equations (2) and (3), the heat treatment time after the film formation of the three-layer structure is obtained. The relationship between the heat treatment temperature T and the shortest heat treatment time τ in the heat treatment is determined. That is, in the method for manufacturing the perpendicular magnetic recording medium according to the second aspect of the present invention, τ ≧ C ₂ (Tc−T) /
If the heat treatment is performed for a heat treatment time τ that satisfies the relationship T,
The magnetization and the axis of easy magnetization can be aligned in the direction of the applied magnetic field H regardless of the direction of the axis of easy magnetization immediately after the hard magnetic pinning layer and the soft magnetic underlayer are formed. For example, when a Co—Zr amorphous soft magnetic film is used as the soft magnetic underlayer, C ₂ = 3.5 and τ ≧ 3.
Heat treatment time τ that satisfies the relationship of 5 (Tc−T) / T
Then, heat treatment may be performed.

According to the method for manufacturing a perpendicular magnetic recording medium according to the second aspect of the present invention, a magnetic field is applied in a fixed direction as in the second prior art when a perpendicular magnetic recording medium having a three-layer structure is formed. No need. Therefore, the freedom of selecting a film forming apparatus is increased, and a large number of films can be formed at once using a film forming apparatus for mass production in which a magnetic field applying structure is difficult at the time of film forming. Then, the magnetization and the axis of easy magnetization of each of the hard magnetic pinning layer and the soft magnetic underlayer of the many perpendicular magnetic recording media can be aligned in a predetermined direction by a magnetic field heat treatment after the film formation. Therefore, even when using a film-forming apparatus for mass production that cannot produce a magnetic field during film formation, a magnetic recording medium with low medium noise with respect to an externally applied magnetic field and high stability of a recording signal with respect to an externally applied magnetic field is used. Easy to get. In addition, since heat treatment in a magnetic field after film formation can be performed in a large amount at a time, productivity is high. Further, it is possible to obtain a high magnetic permeability μ in a high frequency region of several tens of MHz or more.

In the method for manufacturing a perpendicular magnetic recording medium according to the first and second aspects of the present invention, a protective layer may be laminated on the perpendicular magnetic recording layer. Can be performed after a protective layer is laminated on the substrate.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing an embodiment of the present invention, an anisotropic magnetic field Hk defined by the above-mentioned equation (1) will be described.
A constant a indicating the degree of time change of (t), and
A constant K determined by the structure and the material of the magnetic recording medium defined by the equation (2) is experimentally obtained. In an experiment for deriving the constant a and the constant K, in accordance with the method of manufacturing a magnetic recording medium described in the second prior art, a soft magnet underlayer was formed using a DC magnetron sputtering apparatus in the radial direction of the substrate. By applying a magnetic field, a sample was prepared in which the axes of easy magnetization were aligned in the radial direction. That is, as a sample for experimental derivation of the constant a and the constant K: Sample A: On a disk-shaped glass substrate (non-magnetic substrate), a soft magnetic Co91-Zr5-Nb4 at% film (= C
o: 91 at%, Zr: 5 at%, Nb: 4 at%) having a thickness of 600 nm; Sample B: Co83-Sm17at as a hard magnetic pinning layer on a disk-shaped glass substrate (non-magnetic substrate)
% And a soft magnetic Co91-Zr5
Two kinds of samples are prepared by forming a 600 nm Nb 4 at% film. During the film formation, a magnetic field of 2.4 to 5.6 kA / m is applied in the radial direction of the substrate by a magnet of a DC magnetron sputtering apparatus as described in the second prior art, and the hard magnetic pinning layer and the soft magnetic The magnetization and easy axis of the formation are aligned in the radial direction of the substrate. The anisotropic magnetic field Hk of these films is 1.2 kA / m for sample A and 1.4 kA / m for sample B.
Further, the crystallization temperature T of the Co—Zr—Nb film used here
c is about 400 ° C. (670 K).

Next, the films of Sample A and Sample B are cut into rectangles of a predetermined size, respectively.
^In a vacuum of ⁻² Pa or less, a magnetic field of about 40 kA / m was applied in each hard axis direction, and the heat treatment was performed while changing the heat treatment temperature T and the heat treatment time τ. Heat treatment temperature T
= 200 ° C, 250 ° C, and 300 ° C. C at that time
FIG. 4 shows the anisotropic magnetic field Hk of the o-Zr-Nb layer. The anisotropic magnetic field Hk was determined from the MH curve in the direction of the hard axis. The sign of the anisotropic magnetic field Hk is negative in the initial state before the heat treatment, and positive when the axis of easy magnetization matches the direction of the applied magnetic field due to the heat treatment.

FIGS. 5 to 7 show the results as a time change of the anisotropic magnetic field Hk. These time changes can be fitted by the equations shown in the respective figures. Thus, Co-Z in equations (1) and (2)
FIG. 8 shows the calculated constants a and K for the r-based amorphous soft magnetic underlayer.

As is clear from FIGS. 5 to 8, as the heat treatment temperature T increases, the time change of the anisotropic magnetic field Hk becomes sharper, and the value of the constant a increases, whereas the value of the constant K increases. It can be seen that it is almost constant regardless of the heat treatment temperature T and is defined by the structure of the magnetic recording medium and its material. That is, the value of the constant K is 0.14 for sample A and 0.
It can be seen that the value is close to 20. As a result, a constant a indicating the degree of time change of the anisotropic magnetic field Hk (t) defined by the equation (1) and a constant K determined by the structure and the material of the magnetic recording medium defined by the equation (2) Is determined experimentally.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Heat Treatment Apparatus in a Magnetic Field) FIG. 1 is a schematic sectional view of a heat treatment apparatus in a magnetic field for explaining heat treatment in a magnetic field of a perpendicular magnetic recording medium according to an embodiment of the present invention. FIG.
In the magnetic field heat treatment apparatus shown in FIG. 1, a first rare earth permanent magnet 41 with its N pole facing upward is arranged near the center of a vacuum chamber (not shown).
A second rare-earth permanent magnet 42 with its south pole facing upward is arranged so as to orbit around the first permanent magnet 1. And these first and second
Above the rare earth permanent magnets 41 and 42, a substrate holder (not shown) made of a non-magnetic material is arranged, on which a plurality of perpendicular magnetic recording media 21a, 21b, 21c and 21d can be arranged in the vertical direction. . At this time, the polarities of the first and second rare-earth permanent magnets 41 and 42 are such that the upper surface facing the plurality of perpendicular magnetic recording media 21a, 21b, 21c and 21d has
The directions are set to be opposite to each other as shown in FIG. For example, if the upper surface of the first rare earth permanent magnet 41 is an N pole, the upper surface of the second rare earth permanent magnet 42 is an S pole. Further, an infrared (IR) lamp (not shown) such as a halogen lamp is arranged around the substrate holder, and a plurality of perpendicular magnetic recording media 21a, 21b, 21 are provided.
It is configured so that c and 21d can be heated to a constant temperature with good uniformity. In the vacuum chamber not shown,
An evacuation system and a gas introduction system are connected so that an inert gas such as Ar gas can be introduced at a predetermined flow rate via a mass flow controller or the like.

As described above, the heat treatment apparatus in a magnetic field shown in FIG. 1 simultaneously applies a magnetic field H in a certain direction to a large number of perpendicular magnetic recording media and simultaneously performs the heat treatment at a predetermined heat treatment temperature T and heat treatment time τ. It is configured to be heat-treatable.

The first and second rare earth permanent magnets 41,
An electromagnet may be used instead of 42. If an electromagnet is used, a desired magnetic field strength can be freely selected. In any case, the magnetic field H at the time of the heat treatment may be set so as to obtain a magnetic field strength that is large enough to saturate the soft magnetic underlayer with the hard axis.

As the substrate heating method, other methods such as a resistance heating method may be employed in addition to the above-described IR lamp heating method.

(First Embodiment) FIG. 2 shows a first embodiment of the present invention.
FIG. 3 is a partial cross-sectional view schematically illustrating a configuration of a perpendicular magnetic recording medium according to an embodiment. As shown in FIG. 2, this perpendicular magnetic recording medium includes a disk-shaped glass substrate (non-magnetic substrate) 11 having a mirror-polished surface, a soft magnetic underlayer 14 formed on the glass substrate 11 in order, and a perpendicular magnetic recording medium. It comprises a recording layer 15 and a protective layer 16.

In manufacturing the perpendicular magnetic recording medium according to the first embodiment of the present invention, a film forming apparatus for mass production is used. That is, each layer 14, 15, formed on the glass substrate 11,
The film formation of 16 uses a sputtering device for mass production,
Unlike the second conventional technique, no magnetic field is applied in the radial direction of the substrate when forming the soft magnetic underlayer. The film forming conditions are as follows.
C. to 250C. The target is, for example, Co88-Zr7-Nb5at for the soft magnetic underlayer 14.
% Alloy and Co81 for the perpendicular magnetic recording layer 15
Use the -Cr15-Ta4at% alloy, using SiO ₂ as a protective layer 16.

Hereinafter, a method of manufacturing the perpendicular magnetic recording medium according to the first embodiment of the present invention will be specifically described.

(A) First, a plurality of mirror-finished soda-lime glass substrates 11 having a diameter of 95 mm are prepared and fixed on a pallet-type substrate holder to obtain Co88-Zr7.
Soft magnetic underlayer 1 with a target of -Nb 5 at% alloy
4 immediately after forming the film with a thickness of 600 nm, Co81-Cr15-T
perpendicular magnetic recording layer 15 using a4 at% alloy as a target
Is deposited to a thickness of 75 nm. By immediately forming a film here, the perpendicular magnetic recording layer 15 in which Co-Zr-Nb and Co-Cr-Ta are directly bonded and strongly vertically oriented is obtained.
Finally, 10 nm of SiO ₂ is formed as the protective layer 16.

(B) After the film formation is completed in this manner, a magnetic field heat treatment is performed using the magnetic field heat treatment apparatus shown in FIG. That is, the above-described plurality of perpendicular magnetic recording media 21a, 21b, 21c, 21d are placed on a substrate holder (not shown).
And an inert gas such as Ar gas is introduced at a predetermined flow rate via a mass flow controller or the like. And τ ≧
Heat treatment temperature T defined by the relationship of 5 (Tc-T) / T
And heat treatment in a magnetic field while maintaining the heat treatment time τ. In FIG. 1, a first rare earth permanent magnet 41 having an N pole facing upward is disposed, and a second rare earth permanent magnet 4 having an S pole facing upward is arranged so as to circumvent the first rare earth permanent magnet 41.
2 are arranged, so that a plurality of perpendicular magnetic recording media 2
A constant magnetic field H can be applied to each of 1a, 21b, 21c, 21d in the radial direction. The magnetic field H at the time of the heat treatment may be such that the soft magnetic underlayer saturates along the hard axis, for example, a magnetic field H of about 40 kA / m may be applied. FIG. 1 schematically shows lines of magnetic force when there is no perpendicular magnetic recording medium. Actually, the lines of magnetic force are perpendicular to each other in each of the perpendicular magnetic recording media 21a, 21b, 21c, and 21d. It extends in the radial direction of the medium, that is, in the direction parallel to the main surface of the perpendicular magnetic recording medium.

According to the method of manufacturing the perpendicular magnetic recording medium according to the first embodiment of the present invention, the magnetization and the easy axis of the soft magnetic underlayer are changed by the perpendicular magnetic recording by the heat treatment in the magnetic field after the film formation. Since the medium is aligned in the radial direction of the medium, a magnetic recording medium with small medium noise with respect to an externally applied magnetic field can be obtained. In addition, film formation can be performed using a sputtering apparatus for mass production having a pallet-type substrate holder, and heat treatment in a magnetic field after film formation can be performed in a large amount at a time, so that productivity is high. Further, it is possible to obtain a high magnetic permeability μ in a high frequency region of several tens of MHz or more.

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention.
FIG. 3 is a partial cross-sectional view schematically illustrating a configuration of a perpendicular magnetic recording medium according to an embodiment. As shown in FIG. 3, the perpendicular magnetic recording medium includes a mirror-polished disk-shaped glass substrate (non-magnetic substrate) 11, a hard magnetic pinning layer 13 formed on the glass substrate 11, and a soft magnetic layer. It comprises an underlayer 14, a perpendicular magnetic recording layer 15, and a protective layer 16.

In manufacturing the perpendicular magnetic recording medium according to the second embodiment of the present invention, a film forming apparatus for mass production is used. That is, each of the layers 13, 14 formed on the glass substrate 11,
Unlike the second conventional technique, no magnetic field is applied to the substrates 15 and 16 in the radial direction of the substrate during the film formation.

The film forming conditions are such that the gas pressure is 0.067 to 0.13.
In an Ar atmosphere of Pa, the substrate temperature is set to 150 ° C. to 250 ° C.
I do. The target for the hard magnetic pinning layer 13 was
Near the erosion area on Co
Samarium (Sm) chips (size: 5 x 5 x 1 m
m) using a composite target composed of a large number of
You. Further, as a target for the soft magnetic underlayer 14, C
o89-Zr5-Nb4at% alloy, perpendicular magnetic
As a target for the recording layer 15, Co81-Cr15
-Target for protective layer 16 using Ta4 at% alloy
As SiO ₂Use

Hereinafter, a method for manufacturing a perpendicular magnetic recording medium according to the second embodiment of the present invention will be specifically described.

(A) First, a plurality of soda lime glass substrates (non-magnetic substrates) 11 having a mirror finish of 95 mm in diameter are prepared and fixed on a pallet-type substrate holder. The hard magnetic pinning layer 13 is formed to a thickness of 100 to 200 nm using the target as a target. The composition of Sm in the hard magnetic pinning layer 13 varies depending on the number of Sm chips on the composite target, the arrangement relationship, and the sputtering power, but the obtained Sm composition ratio was 11 to 33 at%. Then, Co89-Zr
Immediately after forming the soft magnetic underlayer 14 to a thickness of 600 nm using a 5-Nb4 at% alloy as a target, Co81-Cr15-
Perpendicular magnetic recording layer 1 targeting at 4 at% alloy
5 is deposited to a thickness of 75 nm. By immediately forming a film here, the perpendicular magnetic recording layer 15 in which Co-Zr-Nb and Co-Cr-Ta are directly bonded and strongly vertically oriented is obtained.
Finally, 15 nm of SiO ₂ is formed as the protective layer 16.

(B) After the film formation is completed in this manner, a heat treatment in a magnetic field is performed using the heat treatment apparatus in a magnetic field shown in FIG. That is, the above-described plurality of perpendicular magnetic recording media 21a, 21b, 21c, 21d are placed on a substrate holder (not shown).
And an inert gas such as Ar gas is introduced at a predetermined flow rate via a mass flow controller or the like. And τ ≧
The heat treatment in the magnetic field is performed while maintaining the heat treatment temperature T and the heat treatment time τ defined by the relational expression of 3.5 (Tc−T) / T. In FIG. 1, a first rare earth permanent magnet 41 having an N pole facing upward is arranged.
1 so that the second rare earth permanent magnet 42 with the S pole facing upward is disposed so as to orbit around the first magnetic recording medium 1. Magnetic field H can be applied, and the magnetization and the axis of easy magnetization of the hard magnetic pinning layer 13 and the soft magnetic underlayer 14 are perpendicular to the respective perpendicular magnetic recording media 21a, 21b, 21c, 21.
d are aligned in the radial direction. The magnetic field H at the time of the heat treatment may be such that the soft magnetic underlayer saturates along the hard axis, for example, a magnetic field H of about 40 kA / m may be applied.

According to the method for manufacturing a perpendicular magnetic recording medium according to the second embodiment of the present invention, when the perpendicular magnetic recording medium is formed, as in the second prior art, the film is formed in the radial direction of the substrate during the film formation. There is no need to apply a magnetic field. Therefore, the freedom of selecting a film forming apparatus is increased, and for example, a large number of films can be formed at once using a film forming apparatus for mass production having a pallet-type substrate holder. Then, by heat treatment in a magnetic field after the film formation, the magnetization and the axis of easy magnetization of each of the hard magnetic pinning layer and the soft magnetic underlayer of many perpendicular magnetic recording media can be aligned in the radial direction of each perpendicular magnetic recording medium. It is possible. Therefore, even when a film forming apparatus for mass production is used, it is possible to easily obtain a magnetic recording medium having low medium noise with respect to an externally applied magnetic field and high stability of a recording signal with respect to an externally applied magnetic field. In addition, since heat treatment in a magnetic field after film formation can be performed in a large amount at a time, productivity is high. In addition, several 10M
It is possible to obtain a high magnetic permeability μ in a high frequency region of not less than Hz.

[0044]

According to the method of manufacturing a perpendicular magnetic recording medium of the present invention, even in the case of a perpendicular magnetic recording medium having a two-layer structure, the medium noise is small and the reproducing output is high due to heat treatment in a magnetic field after film formation. It is possible to provide a large amount of recording media at low cost.

According to the method of manufacturing a perpendicular magnetic recording medium of the present invention, the magnetization and the axis of easy magnetization are aligned by heat treatment in a magnetic field after film formation. A film can be formed using a film forming apparatus.
For this reason, it is possible to mass-produce a three-layer magnetic recording medium with low medium noise, high reproduction output, and high signal stability.

According to the method for manufacturing a perpendicular magnetic recording medium of the present invention, it is possible to mass-produce a magnetic recording medium having a high magnetic permeability μ in a high frequency region of several tens of MHz or more.

According to the method for manufacturing a perpendicular magnetic recording medium of the present invention, it is possible to provide a high-performance and high-quality perpendicular magnetic recording medium at low cost and in large quantities.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a magnetic field heat treatment apparatus for performing a magnetic field heat treatment of a perpendicular magnetic recording medium of the present invention.

FIG. 2 is a partial cross-sectional view schematically showing a configuration of the perpendicular magnetic recording medium according to the first embodiment of the present invention.

FIG. 3 is a partial cross-sectional view schematically illustrating a configuration of a perpendicular magnetic recording medium according to a second embodiment of the present invention.

FIG. 4 is a table showing the anisotropic magnetic field Hk when the heat treatment is performed by changing the heat treatment temperature T and the heat treatment time τ in order to experimentally obtain the constant a and the constant K of the present invention.

FIG. 5 shows an anisotropic magnetic field H at a heat treatment temperature T = 200 ° C.
FIG. 7 is a diagram showing a change over time of k.

FIG. 6 shows an anisotropic magnetic field H at a heat treatment temperature T = 250 ° C.
FIG. 7 is a diagram showing a change over time of k.

FIG. 7 shows an anisotropic magnetic field H at a heat treatment temperature T = 300 ° C.
FIG. 7 is a diagram showing a change over time of k.

FIG. 8 is a table showing the results of obtaining constants a and K in equations (1) and (2) using FIGS.

FIG. 9 is a conceptual diagram for explaining a method of forming a film while applying a magnetic field using a DC magnetron sputtering apparatus shown in the second prior art.

[Explanation of symbols]

 Reference Signs List 1 circular substrate 2 chromium layer 3 hard magnetic underlayer 4 soft magnetic underlayer 5 perpendicular magnetic recording layer 6 protective layer 9 rotation center axis 10 perpendicular magnetic recording medium 41 first permanent magnet 42 second rare earth permanent magnet 43 target

Claims (2)

[Claims] 1. A step of forming a soft magnetic underlayer and a perpendicular magnetic recording layer on a non-magnetic substrate to form a multilayer structure, and applying a magnetic field to the multilayer structure in a predetermined direction after the film formation. Performing a heat treatment at a heat treatment temperature T (unit: absolute temperature) and a heat treatment time τ (unit: time) in the state, and aligning the magnetization of the soft magnetic underlayer in the predetermined direction. In the heat treatment time τ, C ₁ is a constant determined by the material of the soft magnetic underlayer and the structure of the magnetic recording medium, and the crystallization temperature of the soft magnetic underlayer is Tc (unit: absolute temperature).
A method for manufacturing a perpendicular magnetic recording medium, wherein the time satisfies the relationship of τ ≧ C ₁ (Tc−T) / T. 2. A hard magnetic pinning layer on a non-magnetic substrate,
A step of forming a soft magnetic underlayer and a perpendicular magnetic recording layer to form a multilayer structure; and after the film formation, the multilayer structure is subjected to a heat treatment temperature T (unit: absolute temperature) while applying a magnetic field in a predetermined direction. And performing a heat treatment for a heat treatment time τ (unit: time) to align the magnetization of the soft magnetic underlayer in the predetermined direction, wherein the heat treatment time τ is C ₂ is a constant determined by the material of the soft magnetic underlayer and the structure of the magnetic recording medium, and the crystallization temperature of the soft magnetic underlayer is Tc (unit: absolute temperature).
A method for manufacturing a perpendicular magnetic recording medium, wherein the time satisfies the relationship of τ ≧ C ₂ (Tc−T) / T.