JPH05114128A - Metallic thin film type magnetic disk medium and production thereof - Google Patents

Abstract

PURPOSE:To control coercive forces and to enable decreasing of noises and high-density recording by forming a magnetic metallic film into two-layered constitutions consisting of a CoCrTa film of a lower layer and a CoCrPt film of an upper layer and properly combining the film thicknesses of both. CONSTITUTION:The magnetic metallic film is made into the plural layer constitutions. The upper layer 32 near a magnetic head 6 is constituted of the CoCrPt having the large coercive force and the lower layer 31 apart from the magnetic head 6 is constituted of the CoCrTa having the small coercive force. The magnetic field to be applied to the magnetic metallic film by the gap G of the magnetic head 6 is strong in the upper layer 32 and is weak in the lower layer 31 and, therefore, the sufficient writing of information is possible and overwriting is easy as well even if the upper layer 32 has the high coercive force. The coercive force can be easily controlled simply by changing the film thickness ratio of the CoCrPt and the CoCrTa.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal thin film magnetic disk medium used as an information recording medium in a magnetic disk device which is an external storage device of a computer system, and a manufacturing method thereof.

With the recent demand for large-capacity storage devices, there is a demand for magnetic disk media having a high recording density. Also,
An easy manufacturing method is required in response to the cost reduction of the recording medium. Therefore, it is necessary that the magnetic disk medium has a structure capable of high density recording and that the magnetic characteristics be easily controlled.

[0003]

2. Description of the Related Art FIG. 7 is a view showing a sectional structure of a conventional metal thin film type magnetic disk medium. B is a substrate made of a non-magnetic material such as aluminum, and Ni formed on the surface of the substrate.
Cr or the like is sputtered as a base film 2 on the P plating layer 1. Then, after a magnetic material such as CoCrTa or CoNiCr is sputtered to form the metal magnetic film 3, carbon is sputtered as the protective film 4, and finally a lubricant 5 such as fomblin is applied and dried to complete the process. ..

In this magnetic disk medium, information is recorded / reproduced on / from the metal magnetic film 3 by the gap G of the magnetic head 6.

[0005]

FIG. 8 is a diagram showing the coercive force of various metal magnetic film materials. As shown in the figure, the coercive force Hc is larger in CoCrTa than in CoNiCr and has excellent S / N characteristics, so that a medium in which CoCrTa is sputtered has been conventionally used as a metal magnetic film. On the other hand, with the increasing density of magnetic recording, CoCrPt
It has been attempted to use a material having a high coercive force such as, but CoCrPt has a problem that the noise is larger than that of CoCrTa.

Moreover, CoCrPt has a too high coercive force under normal film forming conditions, so that the write magnetic field is weak in the lower side of the magnetic film away from the magnetic head, and the writing of data in the lower side of the magnetic film is performed. Is insufficient and the overwrite characteristics are poor. In particular, it is remarkable when data having a small time reversal interval is written on data having a large magnetization reversal interval.

Therefore, in order to satisfy both the noise reduction and the high density recording, an optimum coercive force is required in the metal magnetic film. Conventionally, the control of magnetic properties has been performed by changing the composition of the alloy forming the magnetic film or changing the manufacturing conditions for forming the magnetic film. For example, the thickness of the underlying Cr layer is changed, or the Ar gas pressure when sputtering the metal magnetic film is changed.

However, as is clear from FIG. 8, the range in which the magnetic properties of the magnetic films having the same composition can be taken is considerably limited depending on the composition. Therefore, only by changing the film forming conditions, the optimum magnetic properties can be obtained. It is extremely difficult to obtain the characteristics. Furthermore, it is difficult to control even the distribution of magnetic characteristics in the film thickness direction within the metal magnetic film.

A technical problem of the present invention is to realize such a problem and to realize a magnetic disk medium having a metal magnetic film which can satisfy both of noise reduction and high density recording.

[0010]

FIG. 1 is a sectional view for explaining the basic principle of a metal thin film type magnetic disk medium according to the present invention. According to the invention of claim 1, in the magnetic disk medium in which the magnetic film formed on the non-magnetic substrate B is a metal magnetic film, the metal magnetic film is composed of two layers of a lower layer 31 and an upper layer 32, and the lower layer 31 is The upper layer 32 is made of CoCrTa and the upper layer 32 is made of CoCrPt.

The invention of claim 2 is the lower layer of claim 1.
Reference numeral 31 is a Co-based alloy film having a coercive force Hc of 1000 to 1700 Oe, and the upper layer 32 is a Co-based alloy film having a coercive force Hc of 1500 to 2600 Oe.

The invention according to claim 3 is the lower layer according to claim 1.
31 is composed of 2 to 20 at.% Cr, 2 to 6 at.% Ta and Co.
It is a CoCrTa metal thin film, and the upper layer 32 has a composition of 10 to 20 at.%.
It is a CoCrPt metal thin film composed of Cr, 5 to 15 at.% Pt and Co.

A fourth aspect of the present invention is the method for manufacturing a metal thin film magnetic disk medium according to the first aspect, wherein the film forming gas pressure of the underlayer 2 and the lower layer 31 formed under the lower layer 31 is 20. ~ 30
Select from the range of mTorr, the film forming gas pressure of the upper layer 32 is 3 ~
The film is selected from the range of 30 mTorr.

[0014]

According to the present invention, the metal magnetic film has a multi-layer structure, and the upper layer 32 near the magnetic head 6 is made of Co having a large coercive force.
The lower layer 31 composed of CrPt and separated from the magnetic head 6 is composed of CoCrTa having a small coercive force, but the magnetic field applied to the metal magnetic film at the gap G of the magnetic head 6 is strong in the upper layer 32 and in the lower layer 31. Since it is weak, the upper layer 32 can sufficiently write information even if the coercive force is high, and the overwrite is easy.

Further, the lower layer 31 separated from the magnetic head 6
The CoCrTa constituting the element is made of a material having a small coercive force, but since it has excellent S / N characteristics, noise can be effectively reduced as a whole. Therefore, the upper layer 32 and the lower layer
By the mutual action of 31, the metal thin film magnetic disk medium with reduced noise and high recording density can be realized.

According to a second aspect of the present invention, the lower layer 31 is composed of a Co-based alloy film having a coercive force Hc of 1000 to 1700 Oe, and the upper layer 32 is
By using a Co-based alloy film having a coercive force Hc of 1500 to 2600 Oe, magnetic characteristics such as S / N characteristics and electromagnetic conversion characteristics can be easily controlled.

Also, as in claim 3, the lower layer 31
Is a Co whose composition is 2 to 20 at.% Cr, 2 to 6 at.% Ta and Co.
It is composed of a CrTa metal thin film, and the upper layer 32 has a composition of 10 to 20 at.%.
By using a CoCrPt metal thin film composed of Cr, 5 to 15 at.% Pt and Co, the electromagnetic conversion characteristics can be optimally set by selecting the composition and film thickness ratio of each.

As described in claim 4, the lower layer 31 is formed by increasing the film forming gas pressure of the base film 2 and the lower layer 31 to 20 to 30 mTorr.
Results in low noise. Conventional single-layer film consisting of CoCrTa only 3
However, since there was a problem that the coercive force was too low, the film forming gas pressure of the conventional CoCrTa film was low at 3 to 10 mTorr, but by forming the upper layer 32 of CoCrPt on the CoCrTa layer 31. Since a high coercive force can be obtained, the lower layer 31 can be formed with a high film forming gas pressure which is a low noise film.

[0019]

EXAMPLES Next, practical examples of how the metal thin film magnetic disk medium and the method for manufacturing the same according to the present invention are embodied will be described. In Figure 2, the metal magnetic film is CoCr
The conventional Pt single layer (500 Å) medium and the lower layer 31 according to the present invention
FIG. 4 is a diagram comparing magnetic characteristics of a medium having a two-layer structure of CoCrTa (150Å) and the upper layer 32 of CoCrPt (350Å).

The composition of the upper and lower layers is the lower layer according to claim 3.
31 CoCrTa is 12 at.% Cr, 2 at.% Ta and 86 at.% Co,
The CoCrPt of the upper layer 32 is 15 at.% Cr, 10 at.% Pt and 75 at.% Co.
Is. In addition, each sample was formed into a film on a 5.25-inch NiP-plated aluminum substrate by a static opposed type DC magnetron sputtering apparatus.

To evaluate the electromagnetic conversion characteristics, the gap length 0.45
A thin film magnetic head having a track width of 10 μm, a flying height of 0.14 μm was used. Recording frequency of medium S / Nm characteristics is 14.3MH
z, the noise band is twice that, and the peripheral speed is 19.7 m / s.

White circles and white squares are D50 characteristics (writing frequency when the output decreases to 50%), and the coercive force Hc is 1600 Oe.
In the vicinity, the two-layer structure according to the present invention is larger than that of the conventional CoCrPt single-layer structure, and the characteristics are improved.
Effective for high density recording.

Black circles and black squares have S / N characteristics, and the two-layer structure according to the present invention has a coercive force Hc of about 1600 Oe and CoCrPt
The S / N characteristic is improved by about 2 dB compared to the single layer.

FIG. 3 shows a medium having the above-mentioned CoCrPt single layer structure,
FIG. 6 is a diagram comparing the overwrite characteristics of the two-layered medium according to the present invention. The overwrite characteristic is the residual amount of magnetism of previously written information when it is overwritten at different frequencies in a medium in which information has already been written. The smaller the value, the better.

In this figure, the metal magnetic film having a two-layer structure (white circle) according to the present invention is improved by 3 to 4 dB in the vicinity of Hc1600Oe as compared with the CoCrPt single-layer metal magnetic film shown by the white squares, and the overwrite is overwritten. It has excellent characteristics.

As described above, the lower layer 31 has low noise CoCrTa.
The multi-layer metal magnetic film using high coercive force CoCrPt for the upper layer 32 has improved overwrite characteristics and D50 compared to a CoCrPt single layer film having the same coercive force, and noise reduction is also possible. Excellent electromagnetic conversion characteristics.

FIG. 4 shows a change in coercive force of a two-layered metal magnetic film according to the present invention when the film thickness is constant at 500Å and the film thickness ratio between the lower layer CoCrTa and the upper layer CoCrPt is changed. The result. The film formation was performed by a sputtering method using a stationary facing type DC magnetron sputtering device. The Ar gas pressure during sputtering of the underlying Cr and CoCrTa is
30mTorr, Ar gas pressure during CoCrPt sputtering is 10mTor
It was r.

When the CoCrPt film thickness is first set to zero and is composed of only CoCrTa, like a black triangle, it is about 1000 Oe, whereas the CoCrTa film thickness is gradually decreased and the CoCrPt film thickness is increased. The coercive force gradually increases. Then, when the CoCrTa film thickness is set to zero like a black circle and only the CoCrPt film is formed, the coercive force becomes 2000 Oe or more. However, Co
The average value of Hc of the CrTa single layer film and the CoCrPt single layer film is obtained not when the film thickness ratio of CoCrPt and CoCrTa is 5: 5, but
It was 7: 3.

Thus, according to the present invention, CoCrPt and Co
The coercive force can be easily controlled only by changing the thickness ratio of CrTa. The film thickness can be easily controlled by the sputtering time or the sputtering power.

Further, in this figure, the compositions of CoCrPt and CoCrTa are constant, but by selecting the compositions and changing their coercive forces, the coercive force selection range is further expanded. For example, CoCrTa with a coercive force of 1000 Oe and 2300
If a two-layer film is formed of Oe CoCrPt, a coercive force of 1700 Oe is obtained as a whole. Similarly, CoCrTa with coercive force of 1400 Oe and 2700
When a two-layer film is composed of Oe CoCrPt, a coercive force of 2000 Oe is obtained as a whole, and the coercive force is 1700 Oe CoCrTa and 3000 Oe CoCrPt.
If a two-layer film is constructed with, a coercive force of 2300 Oe can be obtained as a whole. Furthermore, the coercive force can be further increased by adding boron (B) to CoCrPt.

FIG. 5 shows the coercive force of the two-layer film as CoCrTa film thickness.
It shows how it changes depending on the CoCrPt film thickness. For comparison, the results of the CoCrTa single layer film (black triangle) and the CoCrPt single layer film (black circle) are also shown. The horizontal axis is the sum of both film thicknesses, and Co
When the CrTa film thickness is 100Å and the CoCrPt film thickness is increased by 50Å, the white squares are shown. When the CoCrTa film thickness is 150Å, the CoCrPt film thickness is increased by 50Å the white circles, CoCrTa film thickness is 200Å, 50Å
The white rhombus is formed by increasing the CoCrPt film thickness.

The coercive force of the two-layer film according to the present invention increases as the film thickness increases, and becomes saturated from the film thickness of around 300 Å.
This saturation value decreases as the CoCrTa film thickness increases. Also, 2
The Brδ value (δ is the magnetic film thickness) of the layer film is almost determined by the sum of the magnetic film thicknesses regardless of the film thickness ratio of CoCrTa and CoCrPt.

Thus, by appropriately combining the film thicknesses of the two-layer film, the coercive force Hc = 1000 to 2000 Oe and Brδ = 20.
Magnetic characteristics in the range of 0 to 400 G · μm can be easily obtained. That is, the coercive force Hc and Brδ can be freely set by the film thickness ratio between the lower layer CoCrTa and the upper layer CoCrPt.

FIG. 6 shows the change in coercive force due to the Ar gas pressure during sputtering. Black triangles are CoCrTa single layer film, black circles are CoCr
A single layer film of Pt, and a white circle is a two-layer film of CoCrTa and CoCrPt according to the present invention (the film thickness ratio is 7: 3 for CoCrPt: CoCrTa). CoCrPt
It can be seen that in the single-layer film, the coercive force decreases as the Ar gas pressure increases, but in the case of the two-layer film, it increases.
As indicated by the black triangle, the coercive force changes little when CoCrTa or Cr is sputtered, so that a good effect can be obtained on the two-layer film.

When the underlying Cr layer is sputtered, Ar
As the gas pressure increases, the coercive force Hc of the metal magnetic film decreases, but the S / N characteristic of the metal magnetic film improves. Therefore, by increasing the film forming gas pressure of the base film 2 and the lower layer 31 to 20 to 30 mTorr, the lower layer 31 can have low noise. According to the present invention, CoCrPt is formed on the CoCrTa layer 31.
Since a high coercive force can be obtained by forming the upper layer 32 made of, there is no problem even if the lower layer 31 has a low coercive force. In addition,
The film forming gas pressure of the upper layer 32 made of CoCrPt is selected from the range of 3 to 30 mTorr.

[0036]

As described above, according to the present invention, the metal magnetic film in the metal thin film type magnetic disk medium is provided with the lower layer 31
Is a CoCrTa film and the upper layer 32 is a CoCrPt film. By appropriately combining the film thicknesses of both, the coercive force Hc and Brδ can be freely selected, and noise reduction and high density recording can be satisfied. A disk medium can be easily realized.

Further, as in claim 2, the lower layer 31 is composed of a Co-based alloy film having a coercive force Hc of 1000 to 1700 Oe, and the upper layer 32 is
By using a Co-based alloy film having a coercive force Hc of 1500 to 2600 Oe, it is possible to manufacture a metal thin film magnetic disk medium having an optimum electromagnetic conversion characteristic.

As in claim 3, the lower layer 31 has a composition of 2 to
It is composed of a CoCrTa metal thin film composed of 20 at.% Cr, 2-6 at.% Ta and Co, and the upper layer 32 has a composition of 10-20 at.% Cr and 5-15 at.%.
By using a CoCrPt metal thin film composed of Pt and Co, the electromagnetic conversion characteristics can be optimally set by selecting the composition and film thickness ratio of each.

As described in claim 4, by increasing the film forming gas pressure of the base film 2 and the lower layer 31 to 20 to 30 mTorr, the lower layer 31
Is low noise, and coercive force can be secured by the upper layer 32 made of CoCrPt.

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating the basic principle of a metal thin film magnetic disk medium according to the present invention.

FIG. 2 is a diagram comparing magnetic characteristics of a medium having a CoCrPt single-layer metal magnetic film and a metal thin-film magnetic disk medium having a two-layer structure according to the present invention.

FIG. 3 is a diagram comparing the overwrite characteristics of a CoCrPt single layer medium and a double layer medium according to the present invention.

FIG. 4 is a result of measuring a change in coercive force in a metal magnetic film having a two-layer structure according to the present invention when the film thickness is constant and the film thickness ratio of CoCrTa of the lower layer and CoCrPt of the upper layer is changed.

FIG. 5 is a diagram showing how the coercive force of a two-layer film changes depending on the CoCrTa film thickness and the CoCrPt film thickness.

FIG. 6 shows a change in coercive force due to Ar gas pressure during sputtering.

FIG. 7 is a diagram showing a cross-sectional structure of a conventional metal thin film magnetic disk medium.

FIG. 8 is a diagram showing coercive force of various metal magnetic film materials.

[Explanation of symbols]

 B Non-magnetic substrate 1 NiP plating layer 2 Underlayer film (Cr) 3 Conventional metal magnetic film 31 Lower layer in metal thin film 32 Upper layer in metal thin film 4 Protective film 4 5 Lubricant 6 Magnetic head G Gap

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kazuyuki Seki, Kazuyuki Seki, 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Shoji Ishida, 1015, Kamedotachu, Nakahara-ku, Kawasaki, Kanagawa Prefecture, Fujitsu Limited

Claims (4)

[Claims] 1. A magnetic disk medium in which a magnetic film formed on a non-magnetic substrate (B) is a metal magnetic film, wherein the metal magnetic film is composed of two layers, a lower layer (31) and an upper layer (32). A metal thin film magnetic disk medium characterized in that the lower layer (31) is composed of CoCrTa and the upper layer (32) is composed of CoCrPt. 2. The lower layer (31) has a coercive force Hc of 1000-17.
2. The metal thin film magnetic disk according to claim 1, wherein the upper layer (32) is composed of a Co-based alloy film of 00 Oe, and the upper layer (32) is composed of a Co-based alloy film of coercive force Hc of 1500 to 2600 Oe. Medium. 3. The lower layer (31) has a composition of 2 to 20 at.% Cr.
And a CoCrTa metal thin film composed of 2 to 6 at.% Ta and Co, and the upper layer (32) is a CoCrPt metal thin film composed of 10 to 20 at.% Cr, 5 to 15 at.% Pt and Co. The metal thin film magnetic disk medium according to claim 1. 4. The film forming gas pressure of the underlayer (2) and the lower layer (31) formed under the lower layer (31) according to claim 1, is selected from the range of 20 to 30 mTorr, and the upper layer (32). Deposition gas pressure is 3 to 30 mTor
A method of manufacturing a metal thin film magnetic disk medium, characterized in that the film is selected from the range of r.