JP2007257726A - Manufacturing method of magnetic disk, and magnetic disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic disk which has a low medium noise and can obtain a high S/N ratio by suppressing grain growth of a ground layer and also allowing a high orientation property to appear. <P>SOLUTION: In a manufacturing method of a magnetic disk comprising at least a first base layer of an amorphous material, a second base layer of a crystalline material, and a magnetic layer on a disk shape glass substrate, after depositing the above first base layer by reactive sputtering in atmosphere containing an oxidizing gas, the above second base layer is deposited at the substrate temperature in the range from 100 to 240°C. The first base layer comprises any material out of the CoW, CrW, CrTa, CrMo and CoTa. The above oxidizing gas is, for example an oxygen gas and a carbon dioxide gas. Also the above second base layer comprises Cr based alloy of a body centered cubic structure. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a magnetic disk mounted on a magnetic disk device for recording information such as an HDD (hard disk drive).

Today, the information recording technology, particularly the magnetic recording technology, is required to undergo dramatic technological innovation with the development of the IT industry. For example, for a magnetic disk mounted on a magnetic disk device such as an HDD, a technology capable of achieving an information recording density of 100 Gbit / inch ² or more is required.
Such a magnetic disk is particularly required to have an excellent output / medium noise ratio, that is, an S / N ratio. For this reason, conventionally, attempts have been made to improve the magnetic characteristics by reducing the medium noise mainly by reducing the grain size or controlling the crystal orientation.

At such a high recording density, it is also important to have a coercive force (Hc) sufficient to maintain the recorded magnetization. It is known that when the coercive force is low, a signal recorded on the magnetic disk may cause a failure referred to as a so-called thermal fluctuation phenomenon in which the signal is attenuated over time.
The general structure of a conventional magnetic disk is that an amorphous underlayer having a function of refining an upper crystal grain mainly on a disk-shaped glass substrate, and a magnetic layer mainly formed as an upper layer. In this structure, a crystalline underlayer having a function of controlling the crystal orientation and a magnetic layer formed on these underlayers are provided (see, for example, Patent Document 1 and Patent Document 2 below).

JP 2004-86936 A Japanese Patent No. 3217012

By the way, in order to increase the coercive force as much as possible, the conventional magnetic disk usually exposes an amorphous underlayer formed on a glass substrate with oxygen gas, and forms a crystalline underlayer on the amorphous underlayer. It was manufactured by. However, such a conventional manufacturing method requires a chamber for exposing oxygen gas, and the substrate temperature before forming the crystalline underlayer is relatively high in the conventional manufacturing process (250 Therefore, it is difficult to sufficiently suppress the grain growth of the crystalline underlayer. For this reason, the grain size of the magnetic layer formed on the crystalline underlayer can be sufficiently reduced. Therefore, it was difficult to further reduce the medium noise. There is also a problem that the orientation tends to be uneven near the interface between the magnetic layer formed on the crystalline underlayer and the crystalline underlayer, and also causes noise.
The present inventor has found that it is difficult to further improve the magnetic characteristics by sufficiently reducing the medium noise in accordance with the recent demand for accelerated recording density with the prior art.

  The present invention has been made in view of the above-described problems, and its object is to suppress grain growth in the underlayer and to exhibit high orientation (orientation of the easy axis of magnetization of the magnetic layer). Accordingly, it is an object of the present invention to provide a magnetic disk manufacturing method and a magnetic disk that have low medium noise and can obtain a high S / N ratio.

  In order to solve the above-mentioned problems, the present inventor conducted intensive research to suppress grain growth of the underlayer, suitably control the orientation of the magnetic layer, and reduce medium noise. By forming the underlayer by reactive sputtering in an atmosphere containing an oxidizing gas, the substrate temperature for forming a subsequent crystalline underlayer can be lowered. Ascertaining that growth can be suitably suppressed, the present invention having the following configuration has been completed.

(Structure 1) A method of manufacturing a magnetic disk having at least an amorphous first underlayer, a second underlayer, and a magnetic layer on a disk-shaped glass substrate, and in an atmosphere containing an oxidizing gas After the first underlayer is formed by reactive sputtering, the second underlayer is formed at a substrate temperature in the range of 100 ° C. to 240 ° C.
(Structure 2) The magnetic disk manufacturing method according to structure 1, wherein the first underlayer is made of any one of CoW, CrW, CrTa, CrMo, and CoTa.
(Structure 3) The magnetic disk manufacturing method according to Structure 1 or 2, wherein the oxidizing gas is at least one of oxygen gas and carbon dioxide gas.
(Structure 4) The magnetic disk manufacturing method according to any one of Structures 1 to 3, wherein the second underlayer is made of a Cr-based alloy having a body-centered cubic structure.
(Structure 5) The structure according to any one of Structures 1 to 4, wherein a texture along a circumferential direction for inducing magnetic anisotropy is formed in the magnetic layer on the main surface of the disk-shaped glass substrate. The method for manufacturing a magnetic disk according to the above.
(Structure 6) A magnetic disk manufacturing method according to any one of structures 1 to 5, wherein a magnetic layer having an exchange coupling structure is formed on the second underlayer.
(Configuration 7) A magnetic disk obtained by the method for manufacturing a magnetic disk according to any one of Configurations 1 to 6, wherein an easy axis of magnetization of the magnetic layer is oriented substantially parallel to the disk surface. This is a magnetic disk.

In the present invention, as in Configuration 1, the amorphous first underlayer is formed by reactive sputtering in an atmosphere containing an oxidizing gas, so that the subsequent second underlayer (crystalline underlayer) is formed. The substrate temperature for forming the film can be lowered, and the second underlayer can be formed at a low temperature. The low temperature in this case is specifically a substrate temperature in the range of 100 ° C. to 240 ° C. Since the second underlayer can be formed at such a low temperature, the grain growth of the second underlayer can be suitably suppressed. Therefore, the grain size of the magnetic layer formed on the second underlayer can be sufficiently reduced, and the medium noise can be further reduced. In addition, the magnetic layer formed on the second underlayer in which the grains are sufficiently miniaturized can form a highly crystalline magnetic layer without impairing crystal growth from the initial stage of film formation. . Accordingly, it is possible to form a magnetic layer in which the grain size and orientation are suitably controlled, and to reduce the medium noise. As a result, the magnetic characteristics can be improved.

The first underlayer is preferably made of any one of CoW, CrW, CrTa, CrMo, and CoTa, as described in Configuration 2.
As the oxidizing gas, as in Configuration 3, for example, at least one of oxygen gas and carbon dioxide gas can be used.
The second underlayer is preferably made of a Cr-based alloy having a body-centered cubic structure, as in Configuration 4.

Further, as in Configuration 5, by forming a texture along the circumferential direction inducing magnetic anisotropy in the magnetic layer on the main surface of the disk-shaped glass substrate, An excellent magnetic disk can be obtained.
Further, by forming a magnetic layer having an exchange coupling structure on the second underlayer as in Configuration 6, even if the magnetic grain of the magnetic layer is miniaturized, the thermomagnetic aftereffect (thermal fluctuation magnetic aftereffect). ) Can be suppressed.
In the magnetic disk obtained by the present invention, the orientation of the magnetic layer is suitably controlled, and the easy axis of magnetization of the magnetic layer is oriented substantially parallel to the disk surface.

  According to the present invention, it is possible to suppress the grain growth of the underlayer, and to form a magnetic layer in which the grain size and orientation are suitably controlled on the underlayer. A magnetic disk capable of obtaining an S / N ratio can be obtained.

Hereinafter, embodiments of the present invention will be described in detail.
As one embodiment of the magnetic disk according to the present invention, for example, an amorphous first underlayer, a crystalline second underlayer, a magnetic layer, a protective layer, on a disk-shaped glass substrate made of amorphous glass, And a magnetic disk formed by sequentially contacting the lubricating layer.
The glass substrate has a texture formed on its main surface, and the C-axis (easy magnetization axis) of the magnetic layer including the hexagonal close-packed structure (hcp structure) that is sequentially formed in the circumferential direction of the disk A function for preferential orientation is provided. By giving such preferential orientation, a magnetic disk having anisotropy in magnetic characteristics in which the coercive force in the disk circumferential direction of the magnetic disk is larger than the coercive force in the disk radial direction can be obtained.

The glass includes amorphous glass, crystallized glass, and the like. In particular, amorphous glass is suitable for the present invention because it is amorphous and has high surface smoothness. Examples of the material of the glass substrate include aluminosilicate glass, soda lime glass, soda aluminosilicate glass, aluminoborosilicate glass, borosilicate glass, quartz glass, and chain silicate glass. Among these, aluminosilicate glass is suitable for the present invention because it can obtain a smooth surface with high accuracy and can obtain high rigidity by chemical strengthening.

As amorphous aluminosilicate glass, SiO _2: 58~75 wt%, Al ₂ O _3: 5~23 wt%, Li ₂ O: 3~10 wt%, Na ₂ O: 4~13 wt% as a main component It is preferable to consist of the aluminosilicate glass to contain.
Furthermore, the composition of the glass substrate, SiO _2: 62 to 75 wt%, Al ₂ O _3: 5~15 wt%, Li ₂ O: 4~10 wt%, Na ₂ O: 4~12 wt%, ZrO ₂ : Containing 5.5 to 15% by weight as a main component, the weight ratio of Na ₂ O / ZrO ₂ is 0.5 to 2.0, and the weight ratio of Al ₂ O ₃ / ZrO ₂ is 0.4 to An aluminosilicate glass of 2.5 is preferred.
Further, in order to eliminate protrusions on the glass substrate surface caused by the undissolved material of ZrO ₂ , SiO ₂ is 57 to 74%, ZnO ₂ is 0 to 2.8%, Al ₂ O _{3 in} terms of mol%. It is preferable to use a glass for chemical strengthening containing 3 to 15% of Li, 7 to 16% of Li ₂ O and 4 to 14% of Na ₂ O.
Such aluminosilicate glass is chemically strengthened to increase the bending strength, the depth of the compressive stress layer is deep, and the Knoop hardness is excellent.
The thickness of the glass substrate is not particularly limited, but is preferably about 0.1 mm to 1.5 mm.

The texture is not particularly limited as long as the texture induces magnetic anisotropy in the magnetic layer. For example, a circumferential texture, a spiral texture, a cross texture, and the like can be given. In particular, in the case of a circumferential texture, the direction of the texture is similar to the traveling direction of the magnetic head flying and flying over the magnetic disk. Regarding the surface roughness of the texture, Rmax is preferably 6 nm or less, and Ra is preferably 0.6 nm or less. Such a smooth surface roughness can contribute to a high recording density of the magnetic disk. Here, the surface roughness Rmax is the maximum height defined in Japanese Industrial Standard (JIS) B0601, and Ra is the arithmetic average roughness similarly defined in Japanese Industrial Standard (JIS) B0601.
In addition, as a method of forming such a texture, a line is formed on the main surface of the glass substrate by relatively moving the glass substrate and the tape with the resin tape pressed against the main surface of the glass substrate. A tape type texture polishing method for forming a texture is preferred.

The first underlayer has a function of refining grains of each layer formed thereon, and when the glass substrate is made of amorphous glass, an amorphous alloy film is used to correspond to the amorphous glass surface. It is preferable. As a material for the first underlayer, for example, a Co-based alloy such as CoW, CrW, CrTa, CrMo, or CoTa or a Cr-based alloy material is preferably exemplified.
In the present invention, the first underlayer is formed by reactive sputtering in an atmosphere containing an oxidizing gas. The oxidizing gas in this case is preferably oxygen gas or carbon dioxide gas because it is easy to handle. Moreover, you may mix and use these gas.

Further, the temperature at the time of film formation of the first underlayer, the film formation speed, and the degree of vacuum at the time of film formation do not have to be particularly limited in the present invention. A range of 240 ° C. is preferred. Moreover, as a film-forming speed | rate, the range of 40 to 100 to 100 second / second is suitable, for example. Furthermore, the degree of vacuum at the time of film formation is preferably adjusted within a range of, for example, 4 μbar to 12 μbar.
The thickness of the first underlayer can be set as appropriate and is not particularly limited, but is usually in the range of about 50 to 200 mm.

In the present invention, after the first underlayer is formed, the second underlayer is formed at a substrate temperature in the range of 100 ° C. to 240 ° C. According to the present invention, the subsequent second underlayer (crystalline underlayer) is formed by forming the amorphous first underlayer by reactive sputtering in an atmosphere containing an oxidizing gas. The substrate temperature can be lowered, and the second underlayer can be formed at a low temperature. The low temperature in this case is specifically a substrate temperature in the range of 100 to 240 ° C., preferably in the range of 120 to 210 ° C. Since the second underlayer can be formed at such a low temperature, the grain growth of the second underlayer can be suitably suppressed. As a result, a second underlayer having sufficiently fine grains can be obtained. According to the present invention, a magnetic disk having a high coercive force (Hc) can be obtained even when the second underlayer is formed at such a low temperature.

By the way, the second underlayer is oriented so that the easy axis of magnetization (C axis) of the hexagonal close-packed structure (hcp structure) included in the magnetic layer deposited thereon is substantially parallel to the plane of the disk. And a function of suppressing grain coarsening. As the material for the second underlayer, a Cr-based alloy having a body-centered cubic structure (bcc structure) is preferably cited. Can be mentioned.

For example, the second underlayer can be formed using an alloy target having a composition containing Cr and an additive element in an atmosphere containing a rare gas element and an oxygen element. As a film formation method of the second underlayer, reactive sputtering film formation is suitable. When reactive sputtering film formation is performed in an atmosphere containing a rare gas element and an oxygen element, the additive gas contains a rare gas such as Ar (argon) and an oxygen element such as CO ₂ , NO ₂ , and O _2. A mixed gas with gas can be used. As the gas containing an oxygen element mixed with a rare gas, CO ₂ and O ₂ are particularly preferable because they are easy to handle. The mixing ratio of the rare gas and the gas containing oxygen element in the mixed gas used for such reactive sputtering film formation is not particularly limited, but usually the mixing ratio of the gas containing oxygen element to the rare gas is 0.3%. It is appropriate that the amount is in the range of -10% by volume.

The substrate temperature at the time of film formation of the second underlayer is as described above, but the film formation speed and the degree of vacuum at the time of film formation are not particularly limited in the present invention. For example, the range of 40 Å / second to 100 Å / second is suitable. Furthermore, the degree of vacuum at the time of film formation is preferably adjusted within a range of, for example, 4 μbar to 12 μbar.
The second underlayer is preferably formed so as to have a heteroepitaxial relationship with the magnetic layer formed thereon.
Further, the second underlayer may be a single layer, but may be a laminated structure of different materials. The film thickness of the second underlayer can be set as appropriate and is not particularly limited, but is usually in the range of about 50 to 200 mm.

  In the present invention, since the grain growth of the second underlayer can be suitably suppressed, the grain size of the magnetic layer formed on the second underlayer in which the grains are sufficiently miniaturized is sufficiently small. It is possible to further reduce the medium noise. In addition, the magnetic layer formed on the second underlayer in which the grains are sufficiently miniaturized can form a highly crystalline magnetic layer without impairing crystal growth from the initial stage of film formation. . Therefore, a magnetic layer in which the grain size and orientation are suitably controlled can be formed, and the medium noise can be reduced. As a result, the magnetic characteristics can be improved.

The magnetic layer in the present invention is preferably a Co alloy magnetic layer, and particularly preferably a crystalline magnetic layer having a hexagonal close-packed structure (hcp structure). Examples of such a magnetic layer include a CoCr alloy magnetic layer, a CoPt alloy magnetic layer, a CoCrPt alloy magnetic layer, a CoCrPtTa alloy magnetic layer, a CoCrPtB alloy magnetic layer, and a CoCrPtBCu alloy magnetic layer. Since these magnetic layers have a high magnetic anisotropy constant, high magnetic anisotropy can be obtained.
The magnetic layer can be suitably formed by, for example, sputtering film formation using a rare gas such as Ar (argon) as an additive gas. The thickness of the magnetic layer can be set as appropriate, but for example, it is suitable to be in the range of about 50 to 300 mm.

In the present invention, it is preferable that the magnetic layer has an exchange coupling structure including an exchange coupling film. By forming a magnetic layer with an exchange coupling structure, even if the magnetic grain of the magnetic layer is miniaturized, it is possible to suppress thermal fluctuation failure due to thermal magnetic aftereffect (thermal fluctuation magnetic aftereffect), so high recording density It is suitable for conversion. In particular, the coupling is preferably adjusted so that the magnetization direction of the magnetic layer is antiparallel above and below the exchange coupling film. Such adjustment can be obtained, for example, by inserting a non-magnetic layer between the magnetic layers divided up and down and making the non-magnetic layer have a thickness of about 5 to 10 mm, for example. In the case where the magnetic layer is a Co-based alloy ferromagnetic material, the nonmagnetic layer is preferably an Ru layer having an hcp crystal structure or an Ru-based alloy layer.

In the magnetic disk of the present invention, as shown in the present embodiment, a protective layer and a lubricating layer are preferably provided on the magnetic layer. As the protective layer, a carbon-based protective layer is preferable, and a diamond-like protective layer made of amorphous carbon is particularly preferable. The protective layer is particularly preferably formed by a plasma CVD method. Moreover, as a lubricating layer, a perfluoro polyether compound is suitable, for example. The lubricating layer can be formed by a known method such as a dipping method, a spray method, or a spin coating method.
Hereinafter, the embodiment of the present invention will be described more specifically with reference to examples. In addition, this invention is not limited to a following example.

Example 1
The magnetic disk of this example is a magnetic disk obtained by forming a texture on the main surface of a glass substrate made of chemically strengthened amorphous aluminosilicate glass by tape polishing and forming a magnetic layer or the like thereon. It is. Specifically, the magnetic disk 10 of this example (see FIG. 1) was manufactured through the following (1) glass substrate manufacturing process, (2) texture processing process, and (3) film forming process. In the magnetic disk 10 of FIG. 1, an amorphous underlayer 2, body-centered cubic underlayers 3a and 3b, magnetic layers 4a to 4d, a protective layer 5, and a lubricating layer 6 are sequentially in contact with a glass substrate 1. Is formed. The magnetic layer is formed by contacting the stabilization layer 4a, the nonmagnetic layer 4b, the first magnetic layer 4c, and the second magnetic layer 4d, and the first magnetic layer 4c and the first magnetic layer 4c via the nonmagnetic layer 4b. The stabilization layer 4a is a magnetic layer having an exchange coupling structure in which exchange coupling is performed antiparallel. On the glass substrate 1, a circumferential texture for inducing magnetic anisotropy in the circumferential direction is formed in the first magnetic layer 4c.

(1) Glass substrate manufacturing process Amorphous aluminosilicate glass is melted, and the glass disk obtained by direct pressing is subjected to shape processing, grinding, mirror polishing, and a mirror surface state of Rmax 4.5 nm and Ra 0.44 nm. A glass disk was obtained. The glass disk was chemically strengthened to obtain a glass substrate 1. The obtained glass substrate 1 is a 2.5-inch magnetic disk substrate having an outer diameter of 65 mm, an inner diameter of 20 mm, and a plate thickness of 0.635 mm.
Incidentally, aluminosilicate glass in this embodiment, SiO _2: 63.6 wt%, Al ₂ O _3: 14.2 wt%, Li ₂ O: 5.4 wt%, Na ₂ O: 10.4 wt% ZrO ₂ : 6.0% by weight, Sb ₂ O ₃ : 0.4% by weight.

(2) Texture is formed on the main surface of the glass substrate 1 by relatively moving the glass substrate and the tape with the resin tape pressed against the main surface of the glass substrate 1 obtained in the texture processing step (1). Texture processing was performed using the tape type texture polishing method to be formed. Specifically, using a single-wafer rotary tape texture apparatus, a polyester fiber cloth tape was used as the tape, and a diamond slurry in which polycrystalline diamond was dissolved in a dispersant was supplied.
The texture processing conditions at this time are as follows.
Processing pressure: 10 g / mm ²
Substrate rotation speed: 150 rpm
Tape feed rate: 3 mm / second Texture processing time: 50 seconds As described above, a texture having a plurality of lines arranged along the substantially circumferential direction of the disk was formed.

When the fine morphology of the main surface of the obtained glass substrate 1 was observed with an atomic force microscope (AFM), it was confirmed that a predetermined fine texture was formed. At this time, the surface roughness was precisely measured with an atomic force microscope, and it was confirmed that the mirror surface state was 4.81 nm for Rmax and 0.42 nm for Ra. Ra and Rmax were determined in accordance with JIS B0601.
As described above, the nonmagnetic nonmetallic glass substrate 1 for magnetic disk was manufactured.

(3) Film formation process Next, the film formation from the amorphous underlayer 2 to the protective layer 5 is sequentially performed on the glass substrate 1 by a DC magnetron sputtering method using a single wafer stationary opposed film formation apparatus. Went.
That is, first, a sputtering target (hereinafter simply referred to as a target) made of a CoW (Co: 50 at%, W: 50 at%) alloy is used on the glass substrate 1 in an argon gas atmosphere containing 3 mol% oxygen. A base layer 2 of an amorphous alloy made of CoW was formed to a thickness of 100 mm.
Thereafter, the substrate temperature was heated to 200 ° C. to form the body-centered cubic base layers 3a and 3b. First, a CrMn (Cr: 80 at%, Mn: 20 at%) alloy is used as a target, an underlayer 3a made of a CrMn alloy having a thickness of 50 mm is formed in an argon gas atmosphere, and then CrMoTi (Cr: An underlayer 3b made of a CrMoTi alloy with a thickness of 50 mm was formed in an argon gas atmosphere using an alloy of 80 at%, Mo: 15 at%, and Ti: 5 at%.

Next, stabilization of hcp crystal structure made of CoCrTa alloy in an argon gas atmosphere using a target made of ferromagnetic CoCrTa (Co: 85 at%, Cr: 10 at%, Ta: 5 at%) alloy with hcp crystal structure Layer 4a was deposited to a thickness of 30 mm. Next, using a target made of nonmagnetic Ru metal having an hcp crystal structure, the nonmagnetic layer 4b having an hcp crystal structure made of Ru metal in an argon gas atmosphere has a thickness of 7 mm so that antiferromagnetic exchange coupling can be induced. A film was formed to a thickness.
Next, hcp made of CoCrPtB alloy in an argon gas atmosphere using a target made of ferromagnetic CoCrPtB (Co: 61 at%, Cr: 20 at%, Pt: 11 at%, B: 8 at%) alloy having an hcp crystal structure The first magnetic layer 4c having a crystal structure was formed to a thickness of 100 mm. Further, using a target made of a ferromagnetic CoCrPtBCu (Co: 61 at%, Cr: 14 at%, Pt: 10 at%, B: 12 at%, Cu: 3 at%) alloy having an hcp crystal structure, in an argon gas atmosphere, CoCrPtBCu A second magnetic layer 4d having an hcp crystal structure made of an alloy was formed to a thickness of 100 mm. The total thickness of the magnetic layer is 237 mm.

Next, the protective layer 5 was formed on the magnetic layer. Using a carbon target, a protective layer made of hydrogenated carbon was formed to a thickness of 30 mm in an argon gas atmosphere containing 20% by volume of hydrogen. This protective layer 5 is intended to protect the magnetic layer from the impact of the flying magnetic head. Next, a lubricating layer 6 containing a PFPE (perfluoropolyether) compound was formed to a thickness of 10 mm by a dip method. The lubricating layer 6 is for relaxing contact with the flying magnetic head.
The magnetic disk 10 of this example was manufactured as described above.

When the crystal orientation of the Co alloy in the magnetic layer of the magnetic disk 10 of this example obtained was examined using XRD (X-ray diffraction method), it was found that the C axis was oriented substantially parallel to the disk surface. confirmed. That is, the (110) plane of the hexagonal close-packed structure was oriented substantially parallel to the disk surface. Since the easy magnetization axis of the hexagonal close-packed cobalt alloy ferromagnet is parallel to the C axis, the easy magnetization axis of the entire magnetic disk is substantially parallel to the disk surface.
Further, when the magnetic characteristics of the magnetic disk 10 were evaluated using a VSM (vibrating sample type magnetization measuring device), the magnetization curve showed antiferromagnetic exchange coupling, and the magnetization of the stabilization layer 4a and the first It was found that an exchange magnetic field in which the magnetization of the magnetic layer 4c is coupled in antiparallel is generated inside the magnetic disk. The coercive force Hc of the magnetic disk 10 was (4300) Oe, which was a favorable result.

Next, the electromagnetic conversion characteristics (R / W characteristics) of the magnetic disk 10 were evaluated. That is, the medium noise N of the magnetic disk was obtained as the medium integrated noise up to 1.2 times the frequency of DC to 1F after recording a carrier signal with a linear recording density (1F) of 700 kfci. As the reproduction output S, a reproduction output of a signal of 12F recording density was used. The flying height of the magnetic head used for recording / reproducing is 12 nm, and the reproducing element is a GMR type element. When the magnetic disk 10 of this example was evaluated, the S / N ratio was 20.4 dB (see Table 1). This S / N ratio was a satisfactory result as a required value of a magnetic disk that obtains a high recording density of, for example, 100 Gbit / inch ² or more.

(Examples 2 to 7)
The same procedure as in Example 1 was performed except that the material of the amorphous underlayer 2 of Example 1 and the type of oxidizing gas used in sputtering of the underlayer 2 were changed as shown in Table 1. Magnetic disks of Examples 2 to 7 were manufactured.
When the crystal orientation of the Co alloy in the magnetic layer of the obtained magnetic disk of each example was examined using XRD, it was confirmed that the C axis was oriented substantially parallel to the disk surface. For the magnetic disk of each example, the VSM evaluation result was the same as in Example 1.
The S / N ratio of the magnetic disk of each example is 20.1 dB (Example 2), 20.4 dB (Example 3), 20.3 dB (Example 4), 19.1 dB (Example 5), 19.3 dB ( Good results were obtained for both Example 6) and 19.8 dB (Example 7).
The results of the above examples are summarized in Table 1 below.

(Comparative Examples 1-3)
A magnetic disk (Comparative Example 1) was manufactured in the same manner as in Example 1 except that the oxidizing gas was not used when forming the amorphous underlayer 2 in Example 1. A magnetic disk (Comparative Example 2) was manufactured in the same manner as in Example 1 except that the substrate temperature at the time of film formation of the body-centered cubic base layers 3a and 3b in Example 1 was 25 ° C. Further, a magnetic disk (Comparative Example 3) was manufactured in the same manner as in Example 1 except that the substrate temperature at the time of forming the body-centered cubic base layers 3a and 3b in Example 1 was 280 ° C.

The S / N ratios of the magnetic disks of the respective comparative examples were as low as 16.2 dB (Comparative Example 1), 18.3 dB (Comparative Example 2), and 17.6 dB (Comparative Example 3). The results of the above comparative examples are also summarized in Table 1 above.
These results are considered to be due to the fact that the grain and orientation of the magnetic layer are not suitably controlled in the magnetic disks of the comparative examples as compared with the magnetic disks of the examples of the present invention.

(Example 8)
A magnetic disk of Example 8 was manufactured in the same manner as in Example 1 except that the substrate temperature at the time of forming the body-centered cubic underlayers 3a and 3b in Example 1 was set to 160 ° C.
For the magnetic disk of this example, the crystal orientation of the Co alloy in the magnetic layer was examined using XRD, and it was confirmed that the C axis was oriented substantially parallel to the disk surface. For the magnetic disk of this example, the VSM evaluation result was the same as that of Example 1. In addition, the S / N ratio of the magnetic disk of this example was 19.7 dB, which was a good result.

(Comparative Examples 4-6)
A magnetic disk (Comparative Example 4) was prepared in the same manner as in Example 1 except that nitrogen (N ₂ ) gas was used as the reducing gas instead of the oxidizing gas when forming the amorphous underlayer 2 in Example 1. Manufactured. A magnetic disk (Comparative Example 5) was manufactured in the same manner as in Example 1 except that the substrate temperature at the time of film formation of the body-centered cubic base layers 3a and 3b in Example 1 was set to 80 ° C. Further, a magnetic disk (Comparative Example 6) was manufactured in the same manner as in Example 1 except that the substrate temperature at the time of forming the body-centered cubic underlayers 3a and 3b in Example 1 was set to 260 ° C.

The S / N ratios of the magnetic disks of the respective comparative examples were as low as 16.0 dB (Comparative Example 4), 15.2 dB (Comparative Example 5), and 17.1 dB (Comparative Example 6).
These results are considered to be due to the fact that the grain and orientation of the magnetic layer are not suitably controlled in the magnetic disks of the comparative examples as compared with the magnetic disks of the examples of the present invention. The magnetic disk of Comparative Example 4 was an isotropic medium.

It is sectional drawing which shows typically the laminated constitution of the magnetic disc by the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Amorphous underlayer 3a, 3b Body-centered cubic underlayer 4a Stabilizing layer 4b Nonmagnetic layer 4c First magnetic layer 4d Second magnetic layer 5 Protective layer 6 Lubricating layer 10 Magnetic disk

Claims (7)

A method of manufacturing a magnetic disk having at least an amorphous first underlayer, a second underlayer, and a magnetic layer on a disk-shaped glass substrate,
The first underlayer is formed by reactive sputtering in an atmosphere containing an oxidizing gas, and then the second underlayer is formed at a substrate temperature in the range of 100 ° C. to 240 ° C. Production method.   2. The method of manufacturing a magnetic disk according to claim 1, wherein the first underlayer is made of any one of CoW, CrW, CrTa, CrMo, and CoTa.   3. The method of manufacturing a magnetic disk according to claim 1, wherein the oxidizing gas is at least one of oxygen gas and carbon dioxide gas.   4. The method for manufacturing a magnetic disk according to claim 1, wherein the second underlayer is made of a Cr-based alloy having a body-centered cubic structure.   The texture along the circumferential direction that induces magnetic anisotropy in the magnetic layer is formed on the main surface of the disk-shaped glass substrate, according to any one of claims 1 to 4. A method of manufacturing a magnetic disk.   6. The method of manufacturing a magnetic disk according to claim 1, wherein a magnetic layer having an exchange coupling structure is formed on the second underlayer. 7. A magnetic disk obtained by the method of manufacturing a magnetic disk according to claim 1, wherein an easy axis of magnetization of the magnetic layer is oriented substantially parallel to the disk surface. And magnetic disk.

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