JPH05258279A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To improve the coercive force by adding specified elements to a cobalt-nickel-chromium-platinum magnetic film. CONSTITUTION:A magnetic layer containing at least one of nickel and chromium, and cobalt, platinum and boron is formed on a nonmagnetic substrate having a nonmagnetic base layer essentially comprising nickel and phosphorus formed by sputtering. The nickel-phosphorus base layer has an effect to form a desired microstructure and shape of the crystal structure of the magnetic film. The magnetic layer thus formed on the nickelphosphorus base layer shows isotropic magnetic characteristics in the plane direction without influenced by the shape and direction of the texture. Thereby, the obtd. magnetic recording medium has high coercive force even with fine texture, since the magnetic layer is not influenced by the structure of the texture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium such as a magnetic disk device.

[0002]

2. Description of the Related Art In order to achieve high density recording, a magnetic recording medium having a high coercive force and a large signal-to-noise ratio (S / N ratio), and erasing / writing on such a medium having a high coercive force are possible. A head is needed. In recent years, the material of the head has been improved, and the flying height of the head has decreased, resulting in a high coercive force (18
It has become possible to realize high-density magnetic recording using a magnetic recording medium having a magnetic field density of at least 00 Oe. As a magnetic recording medium having a high coercive force that has been reported so far, for example, Japanese Patent Laid-Open No. 3-49021 discloses C on a Cr layer.
It has been shown that oCrNiB is manufactured by applying a negative substrate bias, but the coercive force remains below 2000 Oe.

In addition, Cr / CoCrPtB is about 2500
An example of obtaining the coercive force of Oe has also been reported (Proceedings of the 14th Annual Meeting of the Applied Magnetics Society of Japan, page 29, 1990, 1
(October) However, in a system using a Cr film as a base film, substrate heating at a high temperature (300 ° C.) and a high substrate bias voltage of −200 V are required to obtain a high coercive force, and therefore production stability and yield are improved. There is a problem that is not good.

On the other hand, the flying height of the head must be lowered in order to cope with the future increase in recording density. For this purpose, the texture must be made finer and finer. However, Cr / CoCrP
In the case of the tB system, the coercive force and the recording characteristics are improved by utilizing the concentric circular texture shape on the substrate and aligning the direction of magnetization in the circumferential direction, so that this texture becomes fine. High coercive force and sufficient recording characteristics cannot be obtained (see FIG. 8). Further, when the texture becomes fine, the mechanical sliding property (CSS performance) between the head and the disk deteriorates, so the texture shape is also an important factor when making the texture fine.

That is, when the texture is classified into a groove-like texture and a texture composed of a large number of independent mountains (hereinafter referred to as a mountain-like texture) according to its form, the mountain-like texture is generally more preferable in order to obtain good CSS performance. Can be said to be excellent. However, C
In the case of the r / CoCrPtB system, as described above, the concentric circular texture shape on the substrate is used to improve the coercive force and the recording characteristics. A high coercive force and good magnetic recording characteristics cannot be obtained for a substrate that does not have at all. In other words, the Cr / CoCr proposed so far
In the PtB system, it is difficult to achieve both good recording characteristics and good mechanical characteristics.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems and has a high coercive force and a high S / N ratio that is overwritten (overwritten) even with fine mountain-like textures. It is an object of the present invention to obtain a magnetic recording medium which can be obtained without sacrificing the characteristics and which is excellent in overall characteristics such as corrosion resistance.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is a non-magnetic substrate having a non-magnetic underlayer containing nickel and phosphorus as main components formed by a sputtering method. A magnetic recording medium comprising a magnetic underlayer on which a magnetic layer containing at least one of nickel and chromium and cobalt, platinum and boron is formed.

According to the present invention, at least one of nickel and chromium and cobalt or platinum is formed on the nonmagnetic underlayer of the nonmagnetic substrate having the nonmagnetic underlayer containing nickel and boron as main components formed by the sputtering method. A magnetic recording medium comprising a magnetic layer containing boron and boron.

In the present invention, the magnetic layer formed on a non-magnetic underlayer containing nickel and phosphorus as main components formed by sputtering or a non-magnetic underlayer containing nickel and boron as main components formed by sputtering. Atomic% in layers
In addition, nickel is contained in an amount of 3 to 10%, platinum is included in an amount of 8 to 15%, boron is included in an amount of 0.5 to 6%, and cobalt is included in an amount of 65 to 80%.

In the present invention, the non-magnetic underlayer containing nickel and phosphorus as main components formed by sputtering or the nonmagnetic underlayer containing nickel and boron as main components formed by sputtering is preferably formed on the nonmagnetic underlayer. In the magnetic layer, in atomic%, nickel is 3 to 10%, chromium is 3 to 15%,
It is characterized by containing 8 to 15% of platinum, 0.5 to 6% of boron and 65 to 80% of cobalt.

Further, the present invention is characterized in that the magnetic layer contains 0.5 to 6% in atomic% of one element selected from Ti, Zr, Ta, Mo and W as an additive element.

Further, according to the present invention, a nonmagnetic underlayer containing nickel and phosphorus or nickel and boron as main components is formed on a nonmagnetic substrate by a sputtering method, and at least nickel and chromium are formed on the nonmagnetic underlayer. The present invention provides a method for manufacturing a magnetic recording medium, which comprises sequentially forming a magnetic layer containing one kind and cobalt, platinum and boron.

Magnetic layer (also referred to as magnetic film) in the present invention
Is a CoNiPtB system, a CoNiCrPtB system or C
oCrPtB system.

In the present invention, a required intermediate layer may be provided between the non-magnetic substrate and the non-magnetic underlayer (also referred to as an underlayer), if necessary. For example, a Cr layer having a thickness of about 100 to 500 Å can be provided on the glass substrate in order to enhance the adhesion to the substrate. However, the Cr layer does not affect the recording / reproducing characteristics due to the existence of the non-magnetic underlayer (NiP, NiB).

That is, the underlying film mainly composed of nickel, phosphorus or nickel, boron formed by the sputtering method has a grain structure, but the grains are almost amorphous, and the thickness of the film is below that. It has a sufficient thickness (for example, 5 to 200 nm) to prevent the state of the substrate surface on the side and the presence of a layer for improving the adhesive force, for example, a Cr layer, from affecting the magnetic layer. Moreover, the sputtered nickel-phosphorus layer or nickel-boron layer has reproducibility such that nucleation and crystal growth of the magnetic layer can be controlled,
In addition, it is formed as an underlayer having a uniform surface whose particle size distribution does not depend on the location.

Therefore, the nickel-phosphorus underlayer or the nickel-boron underlayer has a function of making the crystal structure of the magnetic film have a desired microstructure and morphology, and thus the nickel-phosphorus layer or the nickel-boron layer. The present magnetic layer, which has an underlayer of, is not affected by the shape and direction of the texture, and exhibits in-plane isotropic magnetic characteristics. as a result,
The magnetic recording medium according to the present invention can obtain a high coercive force even with a fine texture without being influenced by the texture structure.

The nickel-phosphorus underlayer is Ni in atomic ratio.
_It has a composition in the range of ₅ P to Ni ₂ P (wt% about 10 to 20% phosphorus), and is typically represented by Ni ₃ P (wt% about 10 to 15% phosphorus). The nickel-boron underlayer has a composition in the atomic ratio of Ni ₈₀ B ₂₀ to Ni ₅₀ B ₅₀ , and is typically represented by Ni ₇₅ B ₂₅ .

Comparing these two types of base films, NiB
The grain size of the film is smaller than that of the NiP film. Therefore, as shown in Table 3, CoNiCrPtB
From the viewpoint of S / N ratio when combined with the magnetic film of
The iB film is superior.

As a function of each element in the magnetic layer, the composition range of nickel is 3 to 10%, but if it is less than 3%, the increase in coercive force is small, and if it is more than 10%, the coercive force becomes constant. This is because. Chromium composition range is 3 to 15%
However, if it is less than 3%, the corrosion resistance is poor, and if it is more than 15%, the saturation magnetization and the coercive force are lowered. The composition range of platinum is 8 to 15%, but if it is less than 8%, the coercive force does not increase much, and if it is more than 15%, the saturation magnetization decreases.

Further, boron in the magnetic layer also has a function of making the magnetic particles fine, and therefore, the magnetic particles have an effect of approaching the size of single domain particles, and as a result, a high coercive force can be obtained. It is considered that separation between grains is promoted and a high S / N ratio is obtained. The composition range of boron in which such an effect is recognized is 0.5 to 6 atom%, and more preferably 1.5 to 3.5 atom%. If the proportion of boron is less than 0.5 atom%, the effect of obtaining a high coercive force is insufficient, and if it is more than 6 atom%, the particle size becomes too small, and as a result, a high coercive force cannot be obtained.

On the other hand, deterioration of the squareness (S, S ^* ) is considered as an adverse effect due to the addition of B. Where S =
Mr / Ms (Ms is saturation magnetization, Mr is remanent magnetization)
And S ^* is what is called the coercive force squareness ratio. Generally, if an attempt is made to increase the coercive force due to the separation between grains, S and S ^* will be small, and the overwrite characteristic at the time of recording and reproduction will be deteriorated. It has been found that in order to prevent this, that is, in order to obtain high S and S ^* while maintaining high coercive force, it is effective to add a new element.
That is, Ti, Zr, Ta, M is further added to the magnetic film.
The addition of 0.5 to 6 atomic% of one of refractory metals such as o and W suppresses the reduction of S and S ^* . For example, when Ti is added to the CoNiPtB system, 0.5 to
3 atomic% is a more preferable range, and when Zr is added, 0.5 to 2 atomic% is a more preferable range.

That is, according to the present invention, the underlayer mainly composed of nickel and phosphorus or nickel and boron formed above the non-magnetic substrate by the sputtering method, and the underlayer formed adjacent to the underlayer by the sputtering method. And a magnetic layer.

[0023]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples.

In FIG. 1, the non-magnetic substrate 1 of the magnetic recording medium has an outer diameter of 95 mm, an inner diameter of 25 mm, and a thickness of 1.27 m.
A donut-shaped aluminum disk of m was prepared and the surface of the substrate was lapped. Next, a nonmagnetic metal layer having a thickness of 1 made of nickel-phosphorus is formed on the substrate 1 by electroless plating.
A hard layer 2 having a thickness of 0 μm was provided, the hard layer was polished to a mirror surface, and a texture was formed by a usual means.

Then, nickel-phosphorus or nickel-boron was sputtered on the hard layer 2 of electroless nickel-phosphorus to form a nonmagnetic underlayer 3 made of nickel-phosphorus or nickel-boron. Next, cobalt-nickel-platinum-boron or cobalt-nickel-chromium-platinum-boron was sputtered as the magnetic layer 4 on the nickel-phosphorus underlayer or the nickel-boron underlayer. Next, a carbon film having a thickness of about 250 Å was formed as the protective film 5 by sputtering. Finally, the electromagnetic conversion characteristics of the sample obtained by forming a liquid lubricating layer having a thickness of about 30Å on the carbon film were measured.

In the following Examples 1 to 5, each of the samples has a nickel-phosphorus electroless plating layer as the hard layer 2 and a carbon sputtered film as the protective film 5, and has a non-magnetic underlayer 3
The composition of the magnetic layer 4 was changed. Sputter is Co-Ni
-A co-sputtering method using a Pt or CoNiCrPt target and a CoB target was used.

[Example 1] Cobalt-nickel-platinum-boron magnetic films were formed on the nickel-phosphorus base film having the above composition ratio while changing the boron content, and the coercive force was measured. Fig. 2 (a) shows the change in coercive force with respect to the boron content, and Fig. 2 shows the change in the squareness ratio (S, S ^* ) with respect to the boron content.
It shows in (b). The maximum coercive force was obtained when the boron concentration was about 2 atomic%, and an increase of about 600 Oe was observed as compared with the case without boron. However, at this time, the squareness ratio (S, S ^* )
Is a little decreasing. Corrosion resistance of the magnetic film containing 2 atomic% of boron, which gives the maximum H _C , of 0.62% HNO
_It was evaluated by the decrease in saturation magnetization when immersed in ₃ .
As shown in FIG. 3, the corrosion resistance is also improved by adding 2 atomic% of boron. 2 for cobalt-nickel-platinum magnetic film
Table 1 shows a comparison of the S / N ratios when the atomic% boron was added and when no boron was added. The S / N ratio is also significantly improved by adding boron.

[0028]

[Table 1]

Example 2 The content of titanium was changed on the nickel-phosphorus base film having the above composition ratio (Co ₇₈ Ni ₈ Pt).
Cobalt-nickel-platinum-boron-titanium magnetic film represented by ₁₂ B ₂ ) _1-x Ti _x (x = 0 to 4.3) was formed, and coercive force and squareness ratio (S, S ^* ) were measured. .. The changes of both with respect to the titanium content are shown in FIGS.
Shown in. The increase in coercive force is not remarkable, but the increase in S and S ^* is remarkable, and the effect of titanium addition is clearly recognized.

[Example 3] Nickel-phosphorus having the above composition ratio
By changing the content of zirconium on the base film (Co₇₈Ni
₈ Pt₁₂B₂ )_1-x Zr_x Represented by (x = 0 to 4.3)
Cobalt-nickel-platinum-boron-zirconium
A magnetic film is formed, and coercive force and squareness ratio (S, S ^* ) Is measured
It was The changes of both with respect to the zirconium content
5 (a) and 5 (b). Almost no increase in coercive force
No, but S, S^* Is increasing and zirconium addition
The effect of is recognized.

[Example 4] Cobalt-nickel-chromium-platinum-boron magnetic films were formed on the nickel-phosphorus base film having the above composition ratio while varying the boron content, and the coercive force was measured. The change in coercive force with respect to the boron content is shown in FIG. When the boron concentration was about 2 atomic%, the coercive force became maximum, and an increase of about 900 Oe was observed. The corrosion resistance at this time was evaluated by the reduction of the saturation magnetization when immersed in 0.62% HNO ₃ . As shown in FIG. 7, the corrosion resistance is also improved by adding boron. Cobalt-Nickel-
Table 2 shows a comparison of electromagnetic conversion characteristics when 2 atomic% of boron was added to the chromium-platinum magnetic film and when no boron was added at all. Electromagnetic conversion characteristics are significantly improved overall by adding boron.

[0032]

[Table 2]

[Embodiment 5] A textured substrate having a surface roughness Ra changed was prepared, and cobalt-nickel-chromium-platinum-boron was formed on the nickel-phosphorus base film having the above composition ratio using the substrate. Magnetic film, a sample in which a cobalt-nickel-chromium-platinum-boron magnetic film is formed on the nickel-boron underlayer having the above composition ratio, and a chromium underlayer (5
A sample was prepared by forming a magnetic film of cobalt-chromium-platinum-boron on (00Å thickness). FIG. 8 shows changes in coercive force corresponding to changes in surface roughness. In the case of a chromium underlayer, surface roughness, that is, the magnetic properties are greatly affected by the texture conditions, but in the case of nickel-phosphorus underlayer and nickel-boron underlayers, the coercive force is constant regardless of the texture conditions, Moreover, a high coercive force can be obtained. Table 3 shows the results of comparing the S / N ratios when a substrate having a surface roughness Ra of 34 Å was used and the coercive force was set to 1800 Oe. The S / N ratio is greatly improved by the nickel-boron underlayer as compared with the chromium underlayer.

[0034]

[Table 3]

[Example 6] In Examples 1 and 4 described above, it was shown that the addition of boron improves the corrosion resistance, but increasing the Cr concentration in the CoNiCrPtB alloy also improves the corrosion resistance. It is valid. In this example, the change in corrosion resistance performance when the Cr concentration in the film changed was investigated. That is, a sample in which the Cr concentration in the film is different in the range of 2 to 12% by the co-sputtering method using the Co ₇₈ Ni ₈ Pt ₁₂ B ₂ target and the pure Cr target on the Ni—P base film having the above composition ratio. Was prepared, and the decrease in remanent magnetization when it was immersed in a 0.62% HNO ₃ solution was measured. As shown in FIG. 9, the Cr concentration is 6 atomic%.
The corrosion resistance performance is remarkably improved by the above. In this embodiment, the protective film is not deposited on the magnetic film, but the Cr concentration is 10
If it is more than atomic%, the corrosion resistance is very good even under severe conditions without a protective film. Further, if a protective film having excellent corrosion resistance such as ZrO _{2 is used} as the protective film, there is no problem in practical use even if the Cr concentration is about 6 atomic%. Actually this CoNiCrPt
When the B alloy material is applied to the disc, the Cr concentration according to the required quality may be determined by balancing the improvement of the corrosion resistance due to the increase of the Cr concentration and the reduction of the saturation magnetization and the coercive force.

[0036]

By adding boron to a cobalt-nickel-platinum-based or cobalt-nickel-chromium-platinum-based magnetic film, a high coercive force of 2000 Oe or more required in the future can be obtained.

Further, by using a nickel-boron underlayer film or a nickel-phosphorus underlayer film instead of the conventionally used chromium underlayer film, not only a high coercive force is obtained, but also a high S / N ratio is obtained at the same time. Obtainable.

In particular, the combination of the undercoating film and the magnetic film makes it possible to obtain desired high magnetic characteristics even for a substrate having a fine textured or textureless polished surface, which is required in the future.

Further, boron is added to the magnetic film, or Cr is added.
Since the corrosion resistance is improved by increasing the concentration, it is possible to provide a highly reliable magnetic recording medium.

Since S and S ^* are improved by further adding Ti or Zr to the magnetic film containing boron,
It is possible to prevent the deterioration of the overwrite characteristic at the same time as improving the S / N ratio.

From the above results, the present invention is not affected by the texture of the substrate by using the sputtered film made of nickel-phosphorus or nickel-boron as the non-magnetic undercoat film, and is protected by adding boron to the magnetic layer. It has excellent features that provide a significant increase in magnetic force, improved signal-to-noise ratio and improved corrosion resistance performance.

[Brief description of drawings]

FIG. 1 is a partial sectional view of an embodiment of a magnetic recording medium of the present invention.

FIG. 2 (a) is a graph showing changes in coercive force due to the addition of boron to a cobalt-nickel-platinum magnetic film on a nickel-phosphorus underlayer, (b) cobalt-on a nickel-phosphorus underlayer.
Graph of changes in squareness ratio (S, S ^* ) due to addition of boron to nickel-platinum magnetic film

FIG. 3 is a graph of a corrosion resistance [comparative test] of a cobalt-nickel-platinum-boron magnetic film on a nickel-phosphorus base film.

FIG. 4 (a) is a graph showing changes in coercive force due to addition of titanium to a cobalt-nickel-platinum-boron magnetic film on a nickel-phosphorus underlayer, (b) cobalt-nickel-platinum on a nickel-phosphorus underlayer. -Graph of change in squareness ratio (S, S ^* ) by adding titanium to boron magnetic film

FIG. 5 (a) is a graph showing changes in coercive force due to the addition of zirconium to a cobalt-nickel-platinum-boron magnetic film on a nickel-phosphorus underlayer, (b) cobalt-nickel-platinum on a nickel-phosphorus underlayer. -Graph of change in squareness ratio (S, S ^* ) due to addition of zirconium to boron magnetic film

FIG. 6 is a graph showing changes in coercive force due to addition of boron to a cobalt-nickel-chromium-platinum magnetic film on a nickel-phosphorus underlayer.

FIG. 7 is a graph of corrosion resistance [comparative test] of a cobalt-nickel-chromium-platinum-boron magnetic film on a nickel-phosphorus base film.

FIG. 8 is a graph showing the effect of substrate surface roughness on coercive force.

FIG. 9 is a graph of changes in residual magnetization (corrosion resistance test) of a cobalt-nickel-chromium-platinum-boron magnetic film on a nickel-phosphorus underlayer by immersion in nitric acid.

[Explanation of symbols]

1: Substrate 2: Electroless nickel-phosphorus plating film 3: Nickel-phosphorus base film or nickel-boron base film 4: Magnetic film 5: Protective film

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Tuchen, USA 95030 Monteseleno Gregory Place 18225 (72) Inventor Tustom Tom Yamashita, California 95035 Milpitas Glenview Drive 2305

Claims (6)

[Claims] 1. A nonmagnetic substrate having a nonmagnetic underlayer containing nickel and phosphorus as main components formed by a sputtering method, and at least one of nickel and chromium and cobalt, platinum and boron are deposited on the nonmagnetic underlayer. A magnetic recording medium comprising a magnetic layer containing the same. 2. A nonmagnetic substrate having a nonmagnetic underlayer containing nickel and boron as main components formed by a sputtering method, and at least one of nickel and chromium and cobalt, platinum and boron are deposited on the nonmagnetic underlayer. A magnetic recording medium comprising a magnetic layer containing the same. 3. The magnetic layer according to claim 1, wherein the magnetic layer contains 3 to 10% of nickel, 8 to 15% of platinum, 0.5 to 6% of boron and 65 to 80% of cobalt in atomic%. A magnetic recording medium characterized by the above. 4. The magnetic layer according to claim 1, wherein the magnetic layer has an atomic% of 3 to 10% of nickel, 3 to 15% of chromium, 8 to 15% of platinum, 0.5 to 6% of boron and cobalt. Of 65 to 80% is contained in the magnetic recording medium. 5. The magnetic layer according to claim 1, wherein the magnetic layer contains 0.5 to 6% in atomic% of one element selected from Ti, Zr, Ta, Mo and W as an additive element. Magnetic recording medium. 6. A nonmagnetic underlayer containing nickel and phosphorus or nickel and boron as main components is formed on a nonmagnetic substrate by a sputtering method, and then at least one of nickel and chromium is formed on the nonmagnetic underlayer. And a magnetic layer containing cobalt, platinum, and boron is formed.