JP3041273B2 - Perpendicular magnetic recording medium and magnetic recording / reproducing apparatus using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing device used for an auxiliary storage device of a computer and a magnetic recording medium used for the same.

[0002]

2. Description of the Related Art With the advance of the information age, the amount of information handled on a daily basis has been steadily increasing. Along with this, the demand for higher recording density and higher capacity for magnetic recording devices has become stronger. When the density of the magnetic recording device is increased, the medium area per recording bit is reduced, so that the reproduction output is reduced and the reproduction becomes difficult. In order to solve this problem, a system has been put to practical use in which recording and reproduction are performed by different heads, and a head using a magnetoresistive effect having high sensitivity is used as a reproducing head. Further, in order to increase the density, a head using a giant magnetoresistance effect having higher sensitivity is also being studied. By using such a high-sensitivity reproducing head, the reproducing output can be increased,
At the same time, noise is also amplified, and when a medium with large noise is used, it becomes impossible to read recorded information. Therefore, as a magnetic recording medium for performing high-density recording and reproduction, it is essential to suppress medium noise.

In the in-plane magnetic recording method used for the current magnetic disk, it is essential to make crystal grains fine in order to reduce medium noise. In the future, it will be necessary to secure coercive force and thermally stabilize the recording magnetization state. Sex is expected to be a problem. On the other hand, the perpendicular magnetic recording method has the characteristic that the demagnetizing field decreases as the recording density increases, and when recording at high density, the recording magnetization state is stable and the medium noise is small, and this method is suitable for high density recording. It is believed that there is. Conventionally, perpendicular magnetic recording media have been researched and developed mainly on continuous thin-film magnetic tapes.
Since recording and reproduction are performed with a head having a thickness of at least nm and a wide track width, the reproduction output is large, and it is not necessary to suppress the level of medium noise so much. On the other hand, when a perpendicular magnetic recording medium is used as the magnetic disk, it is necessary to increase the density in the track direction, so that the recording bit area becomes small and the reproduction output becomes very small. Since this small output is reproduced by a high-sensitivity head, it is inevitable that the limit to the medium noise becomes severe, and it is necessary to suppress the output attenuation as much as possible.

[0004] The results of a study on noise in a perpendicular magnetic disk medium are described in, for example, IEEE Transactions on Magnetics3.
3, pp. 3079-3081 (1997), and for CoCrPt perpendicular media, 100 kFCI.
Is shown as 37 dB. However, in order to perform recording and reproduction at a high areal recording density of 10 gigabits per square inch or more, 300 kFCI is required.
Even at the above high linear recording density, a sufficiently high medium S / N is required, and further reduction in medium noise is required. In addition, reports on output attenuation can be found, for example, in IEEE T
This is described in Transactions on Magnetics, Vol. 31, pp. 2755-2775 (1995), and it is considered that a device for suppressing output attenuation even in a perpendicular medium is required.

The (100) of MgO in the CoCr perpendicular magnetization film
For the growth on the surface, see Journal of Applied Physics
57, pages 4003 to 4005 (1985). When CoCr is formed on an MgO single crystal substrate at room temperature, a magnetic film having excellent perpendicular orientation can be obtained, but its coercive force is at most 700 Oersted, which is insufficient for use as a magnetic recording medium.

[0006]

According to our studies,
A Co—Cr—Pt magnetic film is epitaxially grown on the (0001) plane of a nonmagnetic underlayer having a close-packed hexagonal structure such as Co-35 at% Cr, and the film thickness is reduced to make crystal grains of the magnetic film fine. It is known that the noise reduction can be achieved by using such a method. However, when the film thickness is about 25 nm or less, no reduction in noise is observed even when the film thickness is reduced, and there is a limit to the reduction in noise due to the refinement of crystal grains. Further, when the film thickness becomes 15 nm or less, instability of recording magnetization due to thermal fluctuation becomes a problem. Thus, a medium having a high S / N ratio suitable for high-density recording cannot be produced simply by reducing the film thickness and refining the crystal grains.

An object of the present invention is to provide a magnetic recording medium having a sufficiently high medium S / N and capable of holding recorded information for a long period of time, a method of manufacturing the same, and a recording / reproducing apparatus using the magnetic recording medium. Is to do.

[0008]

SUMMARY OF THE INVENTION The above object is attained by (100)
Mg crystal-oriented so that the plane is almost parallel to the film plane
The polycrystalline thin film of O is used as a first base film, and the polycrystalline thin film having a close-packed hexagonal structure in which the (0001) plane is oriented substantially parallel to the film surface is used as a second base film. This is achieved by a magnetic recording medium obtained by forming a perpendicular magnetic film mainly composed of Co and Cr as a magnetic film on the formed magnetic film. In particular, when the main component of the second underlayer is Co, the effect of improving the medium S / N according to the present invention is great, and when the first underlayer is formed on a substrate via a metal thin film. It is easy to obtain the required film strength as a magnetic recording medium.

The perpendicular magnetic recording medium of the present invention is obtained by a manufacturing method in which the first underlayer and the second underlayer are formed at 100 ° C. or lower by a sputtering method, and the magnetic layer is formed at 200 ° C. or higher. Can be That is, a perpendicular magnetic recording medium according to the present invention includes a first underlayer, a second underlayer, and a magnetic layer formed sequentially on a substrate, and the first underlayer has a (100) plane. The second base film is a closest-packed hexagonal polycrystal in which the (0001) plane is crystallographically oriented so as to be substantially parallel to the film surface. Body thin film,
The magnetic film is a perpendicular magnetization film containing Co and Cr as main components. A protective lubrication layer is provided on the magnetic film.

[0010] The first underlayer is preferably formed on a substrate via a metal thin film. Further, the second base film may be a film whose main component is Co. The method for producing a perpendicular magnetic recording medium according to the present invention comprises the steps of forming a MgO polycrystalline thin film having a (100) plane crystallized at 100 ° C. or less on a substrate such that the (100) plane is substantially parallel to the film plane by sputtering. Below 100 ° C, (0001)
Forming a close-packed hexagonal polycrystalline thin film crystal oriented so that the plane is substantially parallel to the film plane;
Forming a perpendicular magnetization film containing Co and Cr as main components at a temperature of not less than ° C.

A magnetic recording / reproducing apparatus according to the present invention is a magnetic recording / reproducing apparatus including a magnetic recording medium, a magnetic recording medium driving section, a magnetic head, a magnetic head driving section, and a recording / reproducing signal processing system. The above-described perpendicular magnetic recording medium of the present invention is used as a medium, and the reproducing section of the magnetic head performs reproduction using a magnetoresistance effect or a giant magnetoresistance effect.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are schematic sectional views showing the basic structure of a perpendicular magnetic recording medium according to the present invention. 1 and 2, reference numeral 11 denotes tempered glass, silicon, carbon, ceramics, a titanium alloy, an organic resin,
A non-magnetic substrate such as a Ni-P alloy-plated aluminum alloy substrate. Reference numeral 12 denotes an MgO polycrystalline underlayer whose crystal orientation is such that the (100) plane is substantially parallel to the film plane. 13 is (0
001) is a close-packed hexagonal polycrystalline underlayer in which the crystal orientation is substantially parallel to the film surface.
oCr and CoRu. 14 is mainly composed of cobalt and chromium, for example, Co-Cr-Ta, Co-Cr-.
Pt, Co-Cr-Pt-Ta, Co-Cr-Nb, C
This is a magnetic recording layer using a ferromagnetic thin film such as o-Cr-W. Reference numeral 15 denotes a protective lubricating layer comprising a protective film of carbon, silicon-carbon, boron-carbon or the like and an organic lubricating film. In FIG. 2, reference numeral 16 denotes Ti, V,
Cr, Ge, Si, Al, Zr, Nb, Mo, Ru, P
It is a metal thin film of d, Ag, Hf, Ta, W, Pt, Au or the like.

[Example 1] A magnetic recording medium having a schematic sectional view shown in FIG. 1 was manufactured. As the non-magnetic substrate 11, _a 2.5 inch diameter tempered glass disk having _a substrate surface roughness _Ra of 3 nm or less is used, and the underlayers 12, 13, the magnetic layer 14, and the protective layer 15 are formed by a DC magnetron sputtering method. Was performed under the following conditions. The ultimate degree of vacuum in the sputtering apparatus is 1 × 10 ⁻⁸ Torr or less, and the argon gas pressure for discharge is 3
× 10 ^-3 Torr, and the input power was 1 kW for a target having a diameter of 6 inches. The evaluation of the medium manufactured in this example was performed by applying a magnetic field in the direction perpendicular to the film surface using a vibrating sample magnetometer for the crystal orientation based on the diffraction intensity measured by the X-ray diffraction method. The coercive force was determined as described above. In order to be a high-resolution and high-S / N perpendicular magnetic recording medium, the magnetic film must have excellent perpendicular orientation and a coercive force of at least 1 kOe.

As a result of forming a 10-nm-thick MgO base film on the substrate at various substrate temperatures and examining the vertical orientation of the MgO film by X-ray diffraction intensity from the MgO (100) plane, FIG. It became like. That is, when formed at a substrate temperature of 100 ° C. or lower, a good (100) orientation film was formed, but when formed at a substrate temperature of 100 ° C. or higher, the orientation in the (100) direction was not good.

Next, the substrate is formed at a substrate temperature of 30 ° C. (10
0) Using two types of MgO film having excellent orientation and an MgO film formed at a substrate temperature of 210 ° C. and having poor (100) orientation as bases, and vertically aligning a magnetic film on them. For the purpose, a 25 nm thick Co-19 at% Cr-
12 at% Pt magnetic films were formed at various substrate temperatures. The substrate temperature dependence of the X-ray diffraction intensity from the (0001) plane of the formed CoCrPt film was measured.
The rPt magnetic film was not vertically aligned. As shown in FIG. 4, in the case of a CoCrPt magnetic film having an MgO film formed at a substrate temperature of 30 ° C. as a base, good vertical alignment was obtained when formed at a substrate temperature of 100 ° C. or less. That is, in order to obtain a CoCrPt magnetic film having excellent vertical orientation,
It has been found that it is necessary to form on a (100) -oriented MgO film at a substrate temperature of 100 ° C. or lower. However, the substrate temperature dependence of the coercive force of a CoCrPt magnetic film with an MgO film formed at a substrate temperature of 30 ° C. is as shown in FIG. 5. Requires a substrate temperature of 200 ° C. or higher, and could not satisfy both the conditions of the vertical orientation and the coercive force.

To solve this problem, an underlayer film having a close-packed hexagonal structure was formed between an MgO underlayer and a magnetic film. Judging from the epitaxial relationship with the CoCr-based magnetic film, it is considered that the alloy film containing Co is preferable as the film having the densest hexagonal structure.
% Non-magnetic CoCr alloy was used. The orientation of the non-magnetic CoCr film on MgO was as shown in FIG. 6 and had exactly the same tendency as in the case of the CoCrPt magnetic film. The vertical axis in FIG. 6 indicates (000) of the nonmagnetic CoCr underlayer.
1) X-ray diffraction intensity from a plane. As a result, 100
By sequentially forming an MgO base film and a CoCr base film at a substrate temperature of not more than ℃, a base film having a (0001) plane of the closest packed hexagonal structure on the outermost surface was obtained.

Under the two layers, a 25 nm-thick CoC
When the rPt magnetic film was formed, the crystal orientation of the magnetic film was as shown in FIG. 7, and generally excellent vertical orientation was obtained. In particular, when the film was formed at a substrate temperature of 200 ° C. or more, better orientation was exhibited. FIG. 8 shows the measured coercive force of these films. When the film was formed at a substrate temperature of 200 ° C. or higher, a sufficiently large coercive force was obtained as a magnetic recording medium.

As a result, at a substrate temperature of 100 ° C. or less, M
After sequentially forming a gO underlayer and a CoCr underlayer, 200 g
By forming the magnetic film at a substrate temperature of not less than ° C., a magnetic film having both perpendicular orientation and coercive force suitable for a perpendicular magnetic recording medium could be formed on an MgO base. Next, Mg
In order to examine the effect of the use of the O underlayer on the recording / reproducing characteristics, three types of disk samples described below were compared. The evaluation of the recording / reproducing characteristics was performed in a spin stand, and the medium S /
The change with time of N and the reproduction output was examined. The evaluation conditions were as follows. Recording was performed by an induction electromagnetic head having a gap length of 0.2 μm, track width of 1 μm, and 20 turns, and reproduction was performed by a magnetoresistive head having a shield interval of 0.2 μm and a track width of 0.9 μm. went. The magnetic spacing between the head and the medium was 40 nm. Reproduction output S is linear recording density 2
kFCI solitary wave output, medium noise N is 300 kFC
The integrated noise of 0 to 50 MHz when I was recorded was measured and obtained, and these ratios were evaluated as the medium S / N. After recording a signal with a linear recording density of 50 kFCI,
The reproduction output was measured from the second to one hour later, plotted against the logarithm of time, and approximated by a straight line to obtain the ratio of the reproduction output after one hour to the one after five seconds. And

A disk sample was prepared as a sample A at 280 ° C. with a 30 nm-thick Ti underlayer film and a 25 nm-thick Co-19 film.
A medium on which an at% Cr-12 at% Pt magnetic film was sequentially formed, a sample B having a Ti underlayer of 30 nm thickness at 280 [deg.] C., a non-magnetic Co-35 at% Cr underlayer of 20 nm thickness, and a Co-19at of 25 nm thickness. % Cr-12at% Pt
A medium on which a magnetic film was sequentially formed, a sample C having a thickness of 10 nm and a non-magnetic Co—
After forming a 35 at% Cr underlayer, a film thickness of 25 at 280 ° C.
This is a medium in which a Co-19 at% Cr-12 at% Pt magnetic film having a thickness of 10 nm is sequentially formed.

The results are shown in Table 1. In Sample C using MgO as the underlayer, higher S / N and higher stability of recording magnetization were obtained. This result indicates that Co-Cr-Ta, Co-Cr-Pt-Ta, Co-C
The results were almost the same when r-Nb and Co-Cr-W were used, and also when Co-Ru was used as the second underlayer.

[0021]

[Table 1]

As described above, the use of MgO as a base improves the stability of S / N and recording magnetization.
Since the O thin film grows in a form in which the crystal grain size is more uniform and the grain boundaries are more clearly separated than the metal thin film, the crystal size of the magnetic film is more uniform and the crystal grain size is larger. This is considered to be due to the fact that a medium in which the magnetic interaction of.

Example 2 When a number of disk samples having the same structure as the sample C described in Example 1 were prepared, some of them had weak film adhesion strength and could not withstand the impact of the head. . This cannot be used as a magnetic recording medium.
An attempt was made to form a thin metal film having a thickness of 30 nm by a DC magnetron sputtering method at a substrate temperature of 30 ° C. As the material of the metal thin film, Ti, V, Cr, Ge, Si, Al, Zr, N
b, Mo, Ru, Pd, Ag, Hf, Ta, W, Pt,
Au and the like were examined, but in each case, the strength of the film was improved with good reproducibility, and there was no problem with the impact of the head. The recording and reproducing characteristics were almost the same as those of the sample C described in Example 1. Therefore, it is desirable to form a metal thin film between the substrate and the MgO underlayer. However,
When the metal thin film was formed at a substrate temperature of 100 ° C. or higher at a thickness of 10 nm or more, although there was no problem in the adhesion strength of the MgO underlayer, the orientation of MgO in the (100) direction was not good. The effect of improving S / N as in Sample C did not occur.

[Embodiment 3] Among the perpendicular magnetic recording media manufactured in the embodiment 1 and the embodiment 2, the medium S / N is 36.
A medium of dB or more was selected, and a magnetic recording / reproducing apparatus using these media was manufactured. The magnetic recording / reproducing apparatus has a well-known structure in which a schematic plan view is shown in FIG. 9A and a schematic cross-sectional view of the magnetic recording medium is shown in FIG. 9B.
And a magnetic head 9 for recording and reproducing by moving on a rotating magnetic recording medium
3. A magnetic head driving unit 94 that drives the magnetic head 93 on the magnetic recording medium 91, supplies a recording signal to the magnetic head,
Further, a recording / reproducing signal processing system 95 for processing a reproducing signal from the magnetic head is provided. The magnetic head 93 used was the same as that used in Example 1, and the magnetic spacing between the magnetic head 93 and the magnetic recording medium 91 was adjusted to be 50 nm or less. As a result, it was confirmed that information could be recorded and reproduced at an areal recording density of 4 gigabits per square inch or more. On the other hand, medium S
When a magnetic recording medium having a / N of less than 36 dB was used, reproduction at a high recording density was difficult.

When an induction electromagnetic head is used as a reproducing head of a magnetic head, there is no difference in medium S / N between the media as seen in the present embodiment, and information recorded at high density It was impossible to regenerate. When a head using the giant magnetoresistance effect is used as the reproducing head,
The difference in medium S / N observed in the present example appeared more clearly, and it was confirmed that the present invention was effective.

[0026]

According to the present invention, a perpendicular magnetic recording medium having a sufficiently high medium S / N suitable for high-density recording and capable of holding recorded information for a long period of time, and a high-performance magnetic recording / reproducing apparatus are provided. Can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a basic cross-sectional structure of a perpendicular magnetic recording medium according to the present invention.

FIG. 2 is a schematic diagram illustrating a basic cross-sectional structure of a perpendicular magnetic recording medium according to a second embodiment.

FIG. 3 is a view showing the substrate temperature dependence of the X-ray diffraction intensity from the (100) plane of the MgO underlayer film formed on the substrate when the film is formed.

FIG. 4 shows C formed on a (100) -oriented MgO substrate.
The figure which showed the substrate temperature dependence at the time of film formation of the X-ray diffraction intensity from the (0001) plane of an oCrPt magnetic film.

FIG. 5 shows C formed on a (100) -oriented MgO substrate.
FIG. 4 is a diagram showing the substrate temperature dependence of the coercive force of an oCrPt magnetic film during film formation.

FIG. 6 is a diagram showing the substrate temperature dependence of the X-ray diffraction intensity from the (0001) plane of the nonmagnetic CoCr underlayer formed on the (100) -oriented MgO underlayer at the time of film formation.

FIG. 7 is a diagram showing the substrate temperature dependence of the X-ray diffraction intensity from the (0001) plane of a CoCrPt magnetic film formed on a (0001) -oriented nonmagnetic CoCr underlayer film during film formation.

FIG. 8 is a diagram showing the substrate temperature dependence of the coercive force of a CoCrPt magnetic film formed on a (0001) -oriented non-magnetic CoCr underlayer during film formation.

FIG. 9 is a schematic diagram of a magnetic recording / reproducing apparatus.

[Explanation of symbols]

11: non-magnetic substrate; 12: MgO polycrystalline thin film (first underlayer) crystal-oriented so that the (100) plane is substantially parallel to the film plane; 13 ... (0001) plane is substantially parallel to the film plane A polycrystalline thin film (second underlayer) having a close-packed hexagonal structure with crystal orientation as follows: 14 ... a perpendicular magnetization film mainly containing Co and Cr; 15 ... a protective lubricating layer; 16 ... a metal thin film; ... magnetic recording medium, 92 ... magnetic recording medium drive unit, 93 ... magnetic head, 94 ... magnetic head drive unit, 95
... Recording / reproducing signal processing system

Continuing from the front page (72) Inventor Kenya Ito 1-280 Higashi-Koigabo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd. In-house (56) References JP-A-7-334832 (JP, A) JP-A-9-320847 (JP, A) JP-A-10-275320 (JP, A) JP-A-10-334444 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B 5/738 G11B 5/64 G11B 5/851

Claims (5)

(57) [Claims] A first base film, a second base film, and a magnetic film which are sequentially formed on a substrate, wherein the first base film has a (100) plane substantially parallel to a film surface. Wherein the second undercoat film is a polycrystalline thin film having a close-packed hexagonal structure in which the (0001) plane is oriented substantially parallel to the film plane. ,
The perpendicular magnetic recording medium according to claim 1, wherein the magnetic film is a perpendicular magnetization film containing Co and Cr as main components. 2. The perpendicular magnetic recording medium according to claim 1, wherein the first underlayer is formed on a base via a metal thin film. 3. The second undercoat film according to claim 1, wherein the main component is Co.
3. The perpendicular magnetic recording medium according to claim 1, wherein: 4. The method according to claim 1, further comprising the steps of:
Forming a MgO polycrystalline thin film having a crystal orientation such that the (100) plane is substantially parallel to the film surface at 0 ° C. or less, and the (0001) plane is substantially parallel to the film surface at 100 ° C. or less. A step of forming a polycrystalline thin film having a close-packed hexagonal structure with crystal orientation, and a step of forming a perpendicular magnetic film mainly containing Co and Cr at 200 ° C. or higher. Production method. 5. A magnetic recording / reproducing apparatus including a magnetic recording medium, a magnetic recording medium driving unit, a magnetic head, a magnetic head driving unit, and a recording / reproducing signal processing system, wherein the magnetic recording medium is used. 4. A magnetic recording / reproducing apparatus using the perpendicular magnetic recording medium according to claim 3, wherein the reproducing section of the magnetic head performs reproduction using a magnetoresistance effect or a giant magnetoresistance effect.