JPH08212531A - Magnetic recording medium and method of manufacturing the same - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to provide a structure and a manufacturing method of a multi-layered magnetic recording medium in which recording noise is less likely to occur when high density recording is performed. [Structure] Cr, Ti, Zr, Al, S on the non-magnetic substrate 6
i, V, Nb, Mo, or a first underlayer 5 made of an alloy whose main component is a metal, a second underlayer 4 made of Ta or Hf, and Cr, V or an alloy thereof. Third underlayer 3 and magnetic layer 2 made of Co alloy
And the protective lubricating layer 1 are sequentially laminated. As compared with the conventional magnetic recording medium having a similar structure, the average coercive force is improved by 10 to 20%, and the normalized noise coefficient is decreased by at least 10% and up to 18%.

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 compatible with high density recording and a method of manufacturing the same.

[0002]

2. Description of the Related Art In the field of magnetic recording, the recording density of information,
The transfer speed is improving rapidly. Therefore, a magnetic disk device and a magnetic tape device capable of high-density writing and reading are required.

In order to realize a magnetic recording medium capable of high density recording, it is necessary to improve the linear recording density and the read signal voltage-to-noise voltage ratio (S / N ratio). To improve the linear recording density, thin the recording film and
It is necessary to increase the coercive force. Further, it is necessary to increase the signal resolution by making the gap between the magnetic head and the distance between the MR element and the magnetic recording medium as close as possible.

In order to improve the S / N ratio, it is necessary to reduce the disturbance of the magnetization pattern of the magnetic recording medium and the noise by reducing the magnetization unit.

The recording film is generally formed on the surface of a disk or tape serving as a substrate. In order to bring the head close to the magnetic recording medium (recording film), the substrate surface must be as flat as possible. Therefore, the disk substrate has been subjected to precision surface polishing.

As a disk substrate, a substrate obtained by plating aluminum with a nickel-phosphorus alloy and polishing the same has been used so far (hereinafter referred to as "nickel-phosphorus substrate"). Further, in recent years, with the miniaturization of magnetic disk devices, non-metal (eg, glass) disk substrates have come to be used. This tendency is particularly strong in the case of using a substrate having a diameter of 65 mm or less and a thin plate thickness.
This is because a non-metal disk substrate such as glass has a hard surface, is easily precision-polished, and is inexpensive.

A magnetic recording medium generally has a structure in which a base layer, a magnetic layer (recording film) and a protective lubricating layer are sequentially formed on a non-magnetic substrate. It is known that it is effective to divide the underlayer into two layers in order to realize a high performance magnetic recording medium. As an example of such a technique, there is a technique disclosed in JP-A-63-187416. The publication describes that, as shown in FIG. 10, by dividing the underlayer into two layers and using a specific material combination and film forming conditions, the modulation of the output voltage and the S / N ratio were improved. ing.

A technique for forming a recording medium when a glass substrate is used is described in JP-A-4-188427.
In this technique, an experiment is conducted with a structure in which a tantalum film is formed on a substrate and a cobalt alloy film is formed on the tantalum film. As a result, a cobalt alloy having a dense hexagonal lattice structure having a (11.0) orientation grows on a chromium alloy having a body-centered cubic lattice structure having a (200) orientation, and electromagnetic conversion characteristics are remarkably improved.

The thin film of Co or Co alloy can have a structure of a dense hexagonal lattice and a face-centered cubic lattice. Among them, the dense hexagonal lattice has high performance as a magnetic recording medium.
Furthermore, as the in-plane recording medium, a dense hexagonal lattice with (11.0) orientation is preferable. The orientation of Co is Cr or C
It is known that the r alloy thin film has a body-centered cubic lattice structure and is formed on the (200) -oriented structure.

For a crystal with a body-centered cubic structure (20
The 0) orientation and the (100) orientation refer to the same orientation. Since only the (200) orientation is detected by measurement such as X-ray diffraction,
The expression (200) orientation is used. In the following, the expression (200) orientation is used.

[0011]

A magnetic recording medium aiming at high density recording requires high coercive force, squareness ratio and low noise. A recording medium in which a chromium layer is formed on a glass substrate via a layer of tantalum or the like has excellent magnetic characteristics and recording / reproducing characteristics. However, since tantalum or the like has poor adhesion to the glass substrate, it has a drawback that it easily peels off. In order to perform high-density recording, it is necessary to reduce the distance between the magnetic head and the recording medium, and the chances of the magnetic head coming into contact with the surface of the magnetic recording medium also increase.
The phenomenon of film peeling is a serious obstacle.

On the other hand, in order to mass-produce magnetic disks, it is necessary that the magnetic recording medium can be easily manufactured by a vacuum equipment having a simple structure.

The present invention provides a substrate suitable for miniaturization (for example,
While using a glass substrate), it has excellent magnetic properties and durability.
An object of the present invention is to provide a magnetic recording medium that realizes reliability (particularly, adhesion between a substrate and an underlayer) and a method for manufacturing the same.

[0014]

The inventor has found that on a chromium alloy having a body-centered cubic lattice structure having a (200) orientation in the direction perpendicular to the substrate surface, a (11.0) orientation in the direction perpendicular to the substrate surface. It was found that the phenomenon in which a cobalt alloy with a close-packed hexagonal lattice structure that grows and that improves the electromagnetic conversion characteristics is also observed when hafnium is formed on a non-metallic substrate. However, it was found that hafnium is also easily separated from the nonmagnetic substrate.

The inventors have investigated various process conditions using various materials. As a result, by forming a thin film layer of a material having excellent adhesion to glass before forming tantalum or hafnium on the glass substrate,
It was found that the drawback of easy peeling can be eliminated. That is, between the substrate and the second underlayer made of tantalum or hafnium, chromium is used as the first underlayer.
It has been found that when a thin film made of titanium, zirconium, aluminum, silicon, vanadium, niobium or molybdenum is formed, the film (second underlayer) thereon cannot be peeled off. It was also found that the first underlayer may be an alloy containing these metals as main components. However, it was also found that some of the metals suitable for use as the first underlayer affect the crystal orientation of the third underlayer formed via the second underlayer. .

When chromium, zirconium, or molybdenum is used as the first underlayer among these materials, the second underlayer made of Ta or Hf is the body-centered cubic lattice of the third underlayer. It was found that the C-axis is strongly oriented in the plane because the crystal composed of (2) has a large effect of (200) orientation and the crystal composed of the dense hexagonal lattice of the magnetic layer thereon is (11.0) oriented. That is, the first underlayer made of chromium, zirconium, and molybdenum does not eliminate the effect of the second underlayer (the effect of orienting the crystals of the third underlayer to (200) orientation).

Therefore, the magnetic recording medium of the present invention has the same magnetic characteristics and low noise characteristics as those of the comparative example, and exhibits high adhesion.

As the first underlayer, titanium other than the above is used,
When aluminum, silicon, vanadium, or niobium is used, the second underlayer forms a crystal of the third underlayer (200).
Since the effect of orientation is slightly inferior, magnetic properties and low noise properties are slightly inferior to those of chromium, zirconium and molybdenum. However, it showed high adhesion and had good reliability as a magnetic disk.

The inventors have also found that this orientation is stronger as the thickness of the second underlayer is smaller.
Although depending on other film characteristics, such an orientation is observed at a film thickness of approximately 150 nm or less. However, the film thickness is 150
It was also found that when the thickness is thicker than nm, the orientation of Cr changes to the (110) direction, which is not desirable. It is also observed that if the thickness of the second underlayer is too thin, a discontinuous film is likely to be formed, and the effect of orienting the C axis in the plane becomes small, and it is preferably 3 nm or more. found.

Furthermore, the inventors have found that this effect tends to be stronger when the surface of the second underlayer is slightly oxidized than when it is not oxidized. A slight oxide layer could be formed by forming the second underlayer and then taking it out of the vacuum chamber and storing it in the atmosphere for a certain period of time. This method is an advantageous manufacturing method because the manufacturing process after taking it out from the vacuum chamber is exactly the same as that of the magnetic disk using the nickel-phosphorus substrate, and the manufacturing can be performed using the conventional apparatus. Is.

It could also be formed by holding in a low pressure atmosphere containing oxygen and water. We also found a method of oxidizing the surface of the second underlayer in a shorter time by a method such as heating or plasma excitation.

Further, the inventors of the present invention produced a magnetic field by forming grooves having directionality on the surface of the second underlayer by mechanical polishing means, and forming the third underlayer and the subsequent layers on the grooves. The recording medium was evaluated. In this recording medium, magnetic anisotropy was recognized, and a magnetic recording medium having excellent magnetic characteristics was obtained.

A magnetic disk device was manufactured using a magnetic disk having such a magnetic recording medium, and the recording / reproducing characteristics and the like were evaluated. The results reflect the characteristics of the magnetic recording medium of which the noise is particularly low, and it is possible to realize a highly reliable magnetic disk device that not only enables writing and reading at high density but also exhibits high strength in contact start / stop tests.

[0024]

The present invention uses chromium, titanium, zirconium, aluminum, silicon, vanadium, niobium or molybdenum, which is a metal material having excellent adhesion (adhesion) to glass and high adhesion to tantalum or hafnium. As a result, the adhesion of the magnetic recording medium film having the multilayer underlayer structure to the substrate was improved. Especially, Cr, Z
When r and Mo are used, excellent magnetic characteristics and recording / reproducing characteristics are realized by simultaneously orienting the easy axis of magnetization of the Co alloy crystal in the in-plane direction by using an underlayer composed of three layers.

[0025]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 schematically shows the internal structure of the magnetic recording medium of this embodiment.

The magnetic recording medium of this embodiment has a non-magnetic substrate 6
A first underlayer 5, a second underlayer 4, a third underlayer 3, a magnetic layer 2, a protective layer, and a lubricating film are sequentially formed on the above. In the figure, the protective layer and the lubricating film are collectively drawn and denoted by reference numeral 1.

A tempered glass was used for the non-magnetic substrate 6.

For the first underlayer 5, chromium, titanium, zirconium, aluminum, silicon, vanadium or niobium was used.

For the second base layer 4, tantalum or hafnium was used.

For the third underlayer 3, a chromium alloy containing 10% of titanium in atomic ratio is used in order to adjust the lattice matching with the magnetic layer.

For the magnetic layer 2, an alloy containing 14 atomic% chromium and 8 atomic% platinum in cobalt was used.

Amorphous carbon was used for the protective layer.

For the lubricating film, a perfluoroalkylpolyether material was diluted with a fluorocarbon solvent and applied.

A method of manufacturing the magnetic recording medium will be described together with manufacturing equipment.

The manufacturing apparatus is a vacuum film forming apparatus, and has pumps and valves for exhausting the gas inside the tank, and electronic and electric circuits for control. However, illustrations of a vacuum pump, a transfer mechanism, a gas introduction mechanism, a vacuum tank stand, etc., which are unnecessary for the description, are omitted.

[Manufacturing Method 1] First, a method of manufacturing a magnetic recording medium by continuous processing in a vacuum chamber without taking out a work into the atmosphere during manufacturing will be described with reference to FIG.

The cleaned work (here, the substrate 8 corresponding to the non-magnetic substrate 6) was conveyed to the heating chamber 10 through the door valve, and then the door valve was closed. The inside of the tank was evacuated by a vacuum pump, and then the heater 11 was turned on to heat the work to about 150 degrees Celsius.

The heated work is placed in the first underlayer forming chamber 13
Was transported through the door valve. And the pressure is 0.6
Argon gas was introduced into the first underlayer forming chamber 13 until the pressure became about Pa. First Underlayer Metal Target 33
A glow discharge plasma 30 was generated on the surface of the work, and a first underlayer 5 having a thickness of 20 nm was formed on the surface of the work arranged in front of the work by sputtering.

Then, in the second underlayer forming chamber 14, the second underlayer 4 of 20 nm was formed on the work.

Subsequently, the work was reheated to about 350 degrees Celsius in the heating chamber 24. The heating was performed by the heater 11.

Further, in the third underlayer forming chamber 15, a Cr / Ti alloy film (third underlayer 3) was formed on the second underlayer 4 to a thickness of about 80 nm.

After that, in the magnetic layer forming chamber 16 and the protective layer forming chamber 17, the magnetic layer 2 and the protective layer 1 were formed. In addition,
The method of forming the magnetic layer 2 and the protective layer 1 is not a feature of the present invention and is a technique that has already been widely used, and thus the description thereof is omitted here. In this way
It was possible to manufacture a magnetic recording medium having the internal structure shown in FIG.

If the work can be conveyed in the opposite direction,
A device configuration in which the heating chamber 24 and the heating chamber 10 are shared may be adopted. In addition, in order to save the time of vacuum evacuation accompanying the loading and unloading of the substrate, a dedicated loading chamber and unloading chamber
You may connect before the heating chamber 10 and after the protection layer formation chamber 17, respectively. Various modifications can be considered for the manufacturing apparatus depending on the difference in the transportation method. For example, an apparatus having a vacuum chamber for both loading and unloading may be used.

However, the manufacturing apparatus must include all means for heating the substrate and means for forming the first underlayer, the second underlayer, the third underlayer, the magnetic layer, and the protective layer. There is.

A second embodiment of the present invention will be described.

In the magnetic recording medium of the second embodiment, as shown in FIG. 3, between the second underlayer 4 and the third underlayer 3, the metal of the second underlayer 4 is formed. It is characterized in that a thin layer (hereinafter, simply referred to as “oxide layer”) 41 containing oxide is provided.

Two types of manufacturing methods of this magnetic recording medium (manufacturing method 2-1 and manufacturing method 2-2) will be described.

[Manufacturing Method 2-1] In this manufacturing method 2-1, the first underlayer 5 and the second underlayer 4 are formed by the apparatus shown in FIG.
The film (layer) after the third underlayer 3 is formed by using the equipment shown in FIG.

In FIG. 4, the work (here, the substrate 8 corresponding to the non-magnetic substrate 6) was conveyed to the heating chamber 10 under atmospheric pressure. Then, the heating chamber 10 was evacuated and then the substrate 8 was heated by the heater 11.

Subsequently, the substrate 8 is placed in the first underlayer forming chamber 1
It was transported to No. 3 and placed in front of the target 33 of the first underlayer metal. Then, a first underlayer 5 of about 20 nm was formed on the surface of the work by the sputtering method.

Next, the door valve on the downstream side of the first underlayer forming chamber 13 is opened, and the work (here, the first underlayer 5) is opened.
The substrate 8) on which was formed was transferred to the second underlayer forming chamber 14 and placed in front of the target 34 of the second underlayer metal. Then, the second underlayer 4 having a thickness of about 20 nm was formed on the work by sputtering.

After this, the vacuum chamber was returned to atmospheric pressure and taken out to the atmosphere through the door valve 12. Then, it was stored in the atmosphere at room temperature for about 5 hours. During the storage, the surface of the second underlayer 4 was oxidized by oxygen in the atmosphere to form an oxide layer 41. After that, as described below, the film (layer) after the third underlayer 3 was formed using the manufacturing equipment of FIG.

In FIG. 5, the work was transferred to the heating chamber 10 and evacuated. Then, the work was heated to about 350 degrees Celsius by the heater 11.

Then, in the third underlayer forming chamber 15, the third underlayer 3 is sputtered to about 8 times.
It was formed with a thickness of about 0 nm. A Cr / Ti alloy was used for the target 35 of the third underlayer metal.

Then, in the magnetic layer forming chamber 16, a cobalt alloy film (magnetic layer 2) was formed on the third underlayer 3 by the sputtering method. Here, the thickness of the cobalt alloy film (magnetic layer 2) was set to about 33 nm.

Thereafter, in the protective layer forming chamber 17, an amorphous carbon film (protective layer) was formed on the magnetic layer 2 by the sputtering method. Here, the thickness of the protective layer is about 15n.
m.

The apparatus shown in FIG. 4 has the same structure as that of a magnetic disk manufacturing apparatus using a nickel-phosphorus substrate. Therefore, the manufacturing process can be easily constructed, and the equipment is not wasted.

[Manufacturing Method 2-2] The Manufacturing Method 2-2 is different from the Manufacturing Method 2-1 in that the oxide layer 41 is formed without taking out the work from the vacuum chamber on the way.

The manufacturing method 2-2 will be described with reference to FIG.

In the heating chamber 10, the first underlayer forming chamber 13 and the second underlayer forming chamber 14, the first underlayer 5 and the second underlayer 4 were formed. The procedure during this time is the above-mentioned manufacturing method
The description is omitted because it is the same as (Production method 2-1).

After this, the work on which the second underlayer 4 was formed was transferred to the heating chamber 24. Then, oxygen was introduced into the heating chamber 24 through the oxidizing gas introduction port 22 to a pressure of about 0.01 Pa. Then, in this atmosphere, the work was heated to about 350 degrees Celsius to oxidize the surface of the second underlayer 4 to form the oxide layer 41.

After that, the third underlayer 3, the magnetic layer 2, and the protective layer 1 are sequentially formed to complete the magnetic recording medium.
The method of forming the third underlayer 3, the magnetic layer 2, and the protective layer 1 may be the same as the above-described manufacturing method, and thus the description thereof is omitted.

The first underlayer 5 and the second underlayer 4 are
It is more desirable to form at a temperature higher than room temperature. However, even if it is formed at room temperature, the adhesion described later is improved. Therefore, the heating chamber 10 of FIGS. 2 and 4 can be omitted. However, when the heating chamber 24 is omitted in the equipment of FIG. 2, the heating chamber 10 cannot be omitted.

As a method of forming the oxide layer 41, various methods other than the above-mentioned method can be considered.

For example, instead of oxygen, steam is used in the heating chamber 2
It is also possible to oxidize the surface of the second underlayer 4 by introducing it into the second underlayer 4. In this case, the steam is introduced so that the pressure in the heating chamber 24 becomes 0.001 to 0.01 Pa. However, when a manufacturing facility with a low degree of vacuum is used, a partial pressure of this level may be obtained without introducing oxygen or water vapor. In that case, it is not necessary to provide a gas inlet. Further, it is possible to form an oxide layer on the surface of the second underlayer 4 by leaving it for 1 hour in an atmosphere containing oxygen or water vapor at about 1 Pa without any particular heating.

It is also possible to oxidize the surface of the second underlayer 4 by applying a voltage to the substrate 8 to generate a discharge. According to this method, the oxide layer 41 can be formed in a short time. When applying this method,
The vacuum chamber shown in FIG. 6 is used by replacing it with the second heating chamber 24 shown in FIG. An oxidizing gas (for example, oxygen, water vapor or a mixed gas thereof) is introduced into the vacuum chamber up to a pressure of about 1 Pa. The oxidizing gas is introduced through the oxidizing gas inlet 22. Then, an AC voltage was applied to the substrate 8 mounted on the substrate holder 9 by the voltage application means 23 to generate glow discharge plasma around the substrate 8 (oxygen plasma treatment). Then, the oxide layer 41 can be formed on the surface of the second underlayer 4 in about 5 seconds by the collision of ionized or excited oxygen or OH.
In the following description, the manufacturing method in which the oxide layer 41 is formed by using the oxygen plasma treatment is referred to as “manufacturing method 2-2 ′”.

The manufacturing apparatus may have various modifications, but means for heating the substrate and means for forming the first underlayer, the second underlayer, the third underlayer, the magnetic layer, and the protective recording layer. And it is necessary to provide all of the oxidation means. A rectangular target may be used depending on the device. Some facilities have different vacuum chamber configurations depending on the transfer method. Further, there is also equipment for sequentially forming a film while transporting it, instead of forming a film while the work is stopped. However, the difference irrespective of the layer structure of the magnetic recording medium does not differ from the manufacturing method of the present invention in essence.

The magnetic recording medium of the present invention is not limited to the above embodiment. In particular, the thicknesses, materials, etc. of the layers mentioned in the description of the manufacturing method are merely examples.

Next, the results of measuring various characteristics (adhesion, magnetostatic characteristics, crystal orientation) of the magnetic recording media of the present invention shown in Examples 1 and 2 will be described with reference to FIG.

The measurement target and measurement method are as follows.

Measurement target (disk type magnetic recording medium) Lubrication layer: Perfluoroalkyl polyether type material diluted with fluorocarbon type solvent and applied Protective layer: Amorphous carbon Magnetic layer 2: Co.Cr.Pt alloy, Thickness 33 nm Third underlayer 3: Cr / Ti alloy, thickness 80 nm Second underlayer 4: material see FIG. 7, thickness 20 nm First underlayer 5: material see FIG. 7, thickness 20 nm Glass substrate 6: aluminosilicate-based tempered glass Outer diameter 65 mm, inner diameter 20 mm, plate thickness 0.635 mm Samples Nos. 1 and 2 are comparative examples, and the first underlayer 5 is not formed.

The samples of sample Nos. 3 to 13 are those of Example 1.
And the oxide layer 41 is not provided (manufacturing method 1).

The samples of sample numbers 14 to 26 correspond to the second embodiment.

The samples Nos. 14 to 15 and 17 to 20 have the oxide layer 41 formed by natural oxidation in the atmosphere (manufacturing method 2-1).

The sample of sample No. 16 is the above-mentioned manufacturing method 2.
It was manufactured by applying -1. However, after the second underlayer 4 was formed and before the third underlayer 3 was formed, texturing was performed to form fine grooves in the circumferential direction. This texturing is
Apply 4 pieces of tape to which alumina abrasive grains (particle diameter about 2 μm) are bonded.
It was performed by pressing the surface of the workpiece rotated at 00 rpm with a pressure of 100 g. After the texturing, it was washed and the third underlayer 3, magnetic layer 2 and protective layer 1 were formed using the equipment shown in FIG.

The samples Nos. 21 to 23 have the oxide layer 41 formed by thermal oxidation in an oxygen atmosphere. (Production method 2-2).

The samples Nos. 24 to 26 are those in which the oxide layer 41 is formed by the oxygen plasma treatment (manufacturing method 2-2 ').

Other detailed specifications which differ for each sample are shown in FIG.

[1] Adhesion measurement method A polyester-based adhesive tape having a high adhesive force was adhered to a magnetic recording medium having a scratch in a grid pattern and peeled off to find out how much the magnetic recording medium film from the substrate. The peeling was measured.

Measurement results and evaluation thereof The ratio of the area where the film remained is shown in FIG. 7 as adhesion.

The samples Nos. 1 and 2 (comparative examples) were completely peeled off.

On the other hand, samples Nos. 3 to 26 (invention) showed high adhesion. Among them, Ti, Z
When r and Mo are used as the first underlayer 5 (sample numbers 4, 5, 10, 11, 12, 14, 15, 16, 18,
Nos. 19, 21, 22, 23, 24, 25, and 26) showed good adhesion regardless of whether the second underlayer 4 was Ta or Hf. It was confirmed that the adhesion of Ta and Hf to the substrate was improved by providing the first underlayer 5 in this manner.

Sample No. 1 which was textured
Regarding the sample of No. 6, no film peeling was observed during the above-mentioned texturing. On the other hand, although the sample of the sample No. 1 (comparative example) subjected to the texturing is not shown in FIG. 7, the Ta film was peeled off from the glass substrate, and it was difficult to use it as a magnetic disk.

[2] Method for Measuring Magnetostatic Characteristics Magnetostatic characteristics were measured with a vibrating sample magnetometer after cutting the sample. The ratio of the coercive force Hc (Th) when a magnetic field is applied in the circumferential direction to the coercive force when applied in the radial direction is defined as the orientation ratio. When the orientation ratio is larger than 1, it means that the coercive force measured in the circumferential direction is larger than the coercive force measured in the radial direction.

Measurement Results and Evaluation In the sample No. 16, the coercive force measured by applying a magnetic field in the circumferential direction was 32.3 kA / m, while the coercive force measured by applying a magnetic field in the radial direction was 26.5kA
Was / m. The orientation ratio was 1.22, which revealed that the film had anisotropy. The value of the coercive force in the circumferential direction is also the largest. Therefore, it was found that the magnetic anisotropy in the circumferential direction was induced by the texturing performed on the surface of the second underlayer 4.

[3] Recording Characteristic Measurement Method Recording characteristics were measured by actually writing a signal in the sample. To measure the most important noise among the recording characteristics, a thin film magnetic head was used to maintain the spatial distance between the surface of the recording layer and the tip of the recording gap at about 50 nm, and at a recording density of 5.5 kbit / mm. Recorded. Then, the normalized noise coefficient was obtained by normalizing the effective value of the disk noise at that time with the peak value of the output voltage when writing at a low frequency. Since the conditions such as track width and peripheral speed are all the same, the relative recording noise of the medium was evaluated based on this normalized noise coefficient.

Measurement Results and Evaluation thereof Sample Nos. 4 and 5 among Sample Nos. 3 to 13
Comparing the normalized noise of the samples of Nos. 7, 11, 12, and 13 with the normalized noise of the samples of Sample Nos. 14 to 20, the noise of the samples of Sample Nos. 14 to 20 is smaller.

Similarly, sample numbers 21 to 23, 24
Normalized noise of the samples of ~ 26 and sample numbers 4, 5,
Comparing with the standardized noise of the 11th sample, the standardized noises of the samples of sample numbers 21 to 23 and 24 to 26 are smaller.

When the cross sections of the samples Nos. 4, 5, and 11 were observed with a transmission electron microscope, it was observed that the oxide layer 41 having a size of several nanometers was formed. From this, it was found that the presence of the oxide layer 41 reduces the normalized Iz coefficient. This shows that the present invention is particularly useful for noise reduction.

It was found that Hf, like Ta, is a suitable material for use as the second underlayer 4.

[3] Crystal Orientation Measurement Target and Measurement Method Samples having various thicknesses of the second underlayer 4 were prepared and used as measurement targets. The conditions (for example, material and manufacturing method) other than the thickness of the second underlayer 4 were the same as those of the sample of Sample No. 5. The crystal orientation was measured by X-ray diffraction.

Measurement Results As a result of X-ray diffraction, the orientation of the CrTi film (third underlayer 3) was (200) and the orientation of the Co alloy film (magnetic layer 2) was (1).
It was found to be 1.0). This state is shown in FIG. In FIG. 8, the horizontal axis represents the thickness of the second underlayer 4. The vertical axis represents Co (1 obtained from the X-ray diffraction spectrum of the sample.
The peak intensities of 1.0) diffraction and Cr (200) diffraction are used.

As the thickness of the second underlayer 4 increases, Cr
The (200) orientation of the Ti film and the (11.0) orientation strength of the Co alloy film decrease. Further, even in a very thin region of 3 nm or less, the orientation strength of these is reduced. Observation by a transmission electron microscope is that the cause of the orientation strength exhibiting such a behavior is that the second underlayer 4 becomes discontinuous in a region where the thickness of the second underlayer 4 is very thin. It turned out from the result. From the above, the layer thickness of the second underlayer 4 is 3 nm.
It is concluded that it is most preferable that the thickness is not less than about 75 nm and not more than about 75 nm. When the thickness of the second underlayer 4 is within such a range, the C-axis of the Cr alloy has a very strong tendency to be oriented in the plane, so that the recording medium has excellent magnetic characteristics and low noise. I understand. However, the normalized noise coefficient was low until the thickness of the second underlayer 4 was about 150 nm.

The characteristics of such crystal orientation are as follows.
Found in all 26 samples, especially Cr, Zr, M
In the case of o, the tendency is strong and the coercive force is high. For other Ti, Al, Si, V and Nb, (11
The peaks of the (0) oriented Cr alloy and the (10.0) oriented Co alloy are slightly observed. Therefore, Cr, Zr,
It can be said that Mo is an excellent first underlayer that improves adhesion without inhibiting the effect of Ta or Hf to orient Cr in the (200) direction.

Next, the results of measuring the characteristics of the magnetic recording medium using a substrate made of a material other than glass will be described with reference to FIG. The measurement / evaluation was performed by the same method as described above. Further, terms (or expressions) indicating various conditions in FIG. 10 have the same meaning as in FIG. 7.

Measurement target (disk type magnetic recording medium) Lubrication layer: Perfluoroalkyl polyether type material diluted with fluorocarbon type solvent and applied Protective layer: Amorphous carbon Magnetic layer 2: Co.Cr.Pt alloy, Thickness 33 nm Third underlayer 3: Cr / Ti alloy, thickness 80 nm Second underlayer 4: tantalum, thickness 20 nm First underlayer 5: See FIG. 9 for material, thickness 20 nm, Substrate 6: For the material, see FIG. 9. Outer diameter 65 mm, inner diameter 20 mm, plate thickness 0.635 mm. Samples Nos. 27 to 30 were obtained by polishing the surface of an amorphous glassy carbon substrate.
As the samples of sample numbers 31 to 37, substrates in which the entire substrate was made of titanium oxide were used. As the samples of sample numbers 35 to 38, those in which an oxide film having a thickness of about 500 nm was formed only on the surface of a polished metal titanium substrate were used.

The samples of sample numbers 30, 34 and 38 are
The surface of the second underlayer was textured.

Other conditions are shown in FIG. The samples of sample numbers 27, 31, and 35 are shown as comparative examples, and the first underlayer is not provided. Further, the data of the above-mentioned sample No. 1 (conventional example using a glass substrate) and sample Nos. 5 and 12 (present invention using a glass substrate) are also shown in FIG.

Sample No. 2 without the first underlayer
Adhesion was 0 to 24% in the samples 7, 31, and 35. This is almost the same as the result of Sample No. 1, and it was difficult to specify it as a magnetic disk. On the other hand, sample numbers 28-30, 32-34, 36-38
Had an adhesiveness of 100%, and the adhesiveness was improved also on these substrates. Sample Nos. 28, 32, 36 (first underlayer: Zr) are Sample Nos. 27, 3
Compared to the 1,35 samples (comparative example), the normalized Neuss coefficient is slightly reduced. Also, the holding force H in the circumferential direction
c is slightly increased.

Sample Nos. 27, 28, 31, 32, 35,
The crystal orientation of 36 samples was examined. as a result,
(200) orientation of chromium alloy and cobalt alloy (11.
It was found that the 0) orientation does not depend on the presence or absence of the first underlayer 5 made of Zr. Further, as in the case of using the glass substrate, Cr and Mo also produced the above orientation. T
Since i, Al, Si, V, and Nb have orientations other than the above, the normalized noise coefficient tends to increase. Therefore, it was found that Zr, Cr, and Mo are suitable as the first underlayer 5 even when such a substrate such as carbon is used.

Sample Nos. 30 and 3 with texture processing
In the samples of Nos. 4 and 38, the orientation ratio was 11.5 to 11.8.
Showed a large value. In addition, magnetic anisotropy having an easy magnetization direction in the circumferential direction was shown. As a result, the holding force in the circumferential direction was improved and the normalized noise coefficient was also improved.

In the above experiment (FIGS. 7 to 9), the aluminosilicate glass was used as the glass substrate.
The effect of the present invention was obtained for other types of glass (for example, soda lime glass and crystallized glass). Further, the above-mentioned various effects are obtained when the thickness of the third underlayer is 3
When the thickness is 00 nm or less, it was obtained almost without depending on the thickness of the third underlayer.

A third embodiment of the present invention will be described.

The magnetic recording medium 8 of the present invention was formed into a disk shape (substrate material: glass, outer diameter: 65 mm, inner diameter: 20 mm, thickness: 0.635 mm, magnetic layer: formed on both sides). Then, the disk-type magnetic recording medium 8 was attached to the rotary shaft, and the thin-film magnetic head, the head drive mechanism, and the recording / reproducing IC were incorporated into a housing to manufacture a magnetic disk device. Linear recording density 3.94 kbit / mm (100 kbit / inch), track density 236 tracks / mm
Recording / reproduction was performed at (6 k tracks / inch), and a good magnetic disk device with a low error occurrence rate was obtained.

The present invention is not limited to the disk type recording medium. Further, it is also applicable to a longitudinal magnetic recording medium such as a magnetic tape using another substrate.

[0107]

The present invention has a great effect that the recording noise is reduced as compared with the noise reduction when reading the magnetic recording medium. The present invention is expected to have the same effect as that of this embodiment not only in the disk type magnetic recording medium but also in the longitudinal recording type magnetic recording medium such as a magnetic tape as long as the same layer structure is adopted.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the internal structure of a magnetic recording medium that is Embodiment 1 of the present invention.

FIG. 2 is a diagram showing equipment for manufacturing the magnetic recording medium of Example 1 by continuous processing in a vacuum chamber.

FIG. 3 is a schematic cross-sectional view showing the internal structure of a magnetic recording medium that is Embodiment 2 of the present invention.

FIG. 4 is a diagram showing an apparatus used for forming first and second underlayers.

FIG. 5 is a diagram showing an apparatus used for forming a third underlayer and the like.

FIG. 6 is a diagram showing an apparatus (oxidizing means) for applying a voltage to a substrate to generate a discharge to form an oxide layer 41 in a short time.

FIG. 7 is a diagram showing measurement results of adhesion, magnetic characteristics and normalized noise coefficient of the magnetic recording medium of the present invention.

FIG. 8 is a diagram showing the results of measuring the crystal orientation of the magnetic recording medium of the present invention by X-ray diffraction.

FIG. 9 is a diagram showing measurement results of characteristics (adhesiveness, magnetic characteristics, normalized noise) of a magnetic disk using a substrate other than glass in the present invention.

FIG. 10 is a diagram showing a conventional technique in which a base layer is divided into two layers.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Protective layer and lubricating film, 2 ... Magnetic layer, 3 ... 3rd underlayer, 4 ... 2nd underlayer, 5 ... 1st underlayer, 6 ...
Non-magnetic substrate, 8 ... Magnetic disk substrate, 9 ... Substrate holder, 10 ... Heating chamber, 11 ... Heater, 12 ... Door valve, 13 ... First underlayer forming chamber, 14 ... Second underlayer forming chamber, 15 ... Third base film layer forming chamber, 1
6 ... Magnetic layer forming chamber, 17 ... Protective layer forming chamber, 22 ... Oxidizing gas inlet, 23 ... Voltage applying means, 24 ... Second heating chamber, 30 ... Glow discharge plasma, 33 ... First underlayer metal Target, 34 ... Target of second underlayer metal, 35 ... Target of third underlayer metal,
36 ... Target of magnetic layer metal, 37 ... Target of protective film material, 41 ... Oxide film of second underlayer metal

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shioji Fujita 2880, Kozu, Odawara, Kanagawa Stock Company Hitachi Storage Systems Division (72) Inventor Kenji Furusawa 2880, Kozu, Odawara, Kanagawa Hitachi, Ltd. Storage System Division

Claims (9)

[Claims] 1. A magnetic recording medium comprising a non-magnetic substrate on which a base layer made of a non-magnetic metal is formed, and a magnetic layer made of an alloy containing cobalt is formed on the base layer. From the side on the non-magnetic substrate, Cr, Ti, Zr,
A first underlayer made of Al, Si, V, Nb, Mo, or an alloy mainly containing these metals, and a second underlayer made of Ta, Hf, or an alloy mainly containing each of them, and Cr. , V or a third underlayer made of an alloy containing these as main components, and a structure in which the third underlayer is sequentially laminated. 2. A magnetic recording medium in which an underlayer made of a nonmagnetic metal is formed on a nonmagnetic substrate, and a magnetic layer made of an alloy containing cobalt is formed on the underlayer. From the side above the non-magnetic substrate, the first underlayer made of Cr, Zr, Mo, or an alloy containing these metals as the main components, and the second underlayer made of Ta, Hf, or an alloy containing each of these components as the main component. A third layer consisting of a stratum and Cr, V or an alloy containing these as the main components, whose crystal structure is a body-centered cubic lattice, and whose orientation direction is the (100) direction perpendicular to the substrate surface of the substrate. In the magnetic layer, the crystal structure is a dense hexagonal lattice, and the orientation direction is perpendicular to the substrate surface of the substrate (11.
0) The magnetic recording medium is characterized by having a direction. 3. The magnetic recording medium according to claim 1, wherein the second underlayer has a thickness of 3 nm or more and 150 nm or less. 4. A layer containing an oxide of a metal forming the second underlayer is further provided between the second underlayer and the third underlayer. Item 1. The magnetic recording medium according to Item 1, 2 or 3. 5. The at least second underlayer comprises the third
5. The magnetic recording medium according to claim 1, wherein the magnetic recording medium has a groove having directionality at the interface on the underlayer side. 6. The magnetic recording medium according to claim 1, 2, 3, 4 or 5, wherein the non-magnetic substrate is glass, carbon or titanium oxide. 7. A method of manufacturing a magnetic recording medium, wherein sputtering of Cr, Ti,
A first underlayer made of Zr, Al, Si, V, Nb, Mo, or an alloy containing these metals as a main component, and a second underlayer made of Ta, Hf or an alloy containing each of them as a main component. Are sequentially formed on a non-magnetic substrate or a substrate whose surface is at least non-metallic, and then the substrate on which the first underlayer and the second underlayer are formed is once taken out from the vacuum chamber and then again. After returning to the vacuum chamber, a third underlayer made of Cr, V or an alloy containing these as a main component is formed, and a magnetic layer is further formed on the third underlayer. And a method for manufacturing a magnetic recording medium. 8. Forming directional fine grooves on the surface of the second underlayer after forming the second underlayer and before forming the third underlayer. The method of manufacturing a magnetic recording medium according to claim 7, wherein 9. A magnetic recording medium according to claim 1, 2, 3, 4 or 5, write means for writing a signal to the magnetic recording medium, and read means for reading a signal from the magnetic recording medium. A magnetic recording device comprising: at least one of