JPH08329444A - Magnetic recording medium - Google Patents

Abstract

PURPOSE: To attain high coercive force without reducing S-N ratio. CONSTITUTION: A nonmagnetic underlayer of Cr, an intermediate layer of a Co-base alloy having an hcp structure and a magnetic layer of a Co alloy are successively formed on a nonmagnetic substrate. The ratio (BsIL.tIL/ BsML.tML) of the product (BsIL.tIL) of the saturation magnetic flux density (BsIL) of the intermediate layer and the thickness (tIL) of the intermediate layer to the product (BsML.tML) of the saturation magnetic flux density (BsML) of the magnetic layer and the thickness (tML) of the magnetic layer is regulated to <=0.2.

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, and more particularly to an in-plane magnetic recording medium used in a magnetic recording device such as a magnetic disk device, a floppy disk device, a magnetic tape device or the like.

[0002]

2. Description of the Related Art In recent years, the range of application of magnetic recording devices such as magnetic disk devices, floppy disk devices, magnetic tape devices, etc. has been remarkably expanded and its importance has increased, and the magnetic recording media used in these devices have The recording density is being significantly improved.

Regarding these magnetic recording media,
Further, it is required to achieve higher recording density, and therefore, it is required to achieve higher coercive force of the magnetic recording layer and higher signal-to-noise ratio.

Among these, as an effective means of increasing the coercive force, Pt is added to the magnetic material to obtain 2000 O
It is known that a high coercive force exceeding e can be obtained.
For example, Japanese Patent Laid-Open No. 59-88806 discloses a Co-based material, and USP No. 5,024,903 discloses an example in which Pt is added to a CoCrTa-based material.

[0005]

However, although the addition of Pt is effective in improving the coercive force, it also increases the medium noise. A magnetic recording medium formed with a CoPt-based magnetic layer has a higher medium noise than a magnetic recording medium formed with a magnetic layer having a relatively low coercive force such as CoCrTa. As a method of reducing medium noise, a method is known in which a magnetic layer is multi-layered and a non-magnetic layer is inserted between them (Japanese Patent Laid-Open No. 6-176341, etc.). The magnetic force tends to decrease, and the current means is that no powerful means for achieving both high coercive force and low noise has been developed yet.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above conventional circumstances, and has a high coercive force in a magnetic recording medium without reducing the signal / noise ratio (S / N ratio). It is an object of the present invention to provide a magnetic recording medium that realizes

The magnetic recording medium according to the present invention is a magnetic recording medium having a non-magnetic substrate, a Co-based alloy magnetic layer (ML), and a non-magnetic underlayer containing Cr as a main component between the magnetic layer and the substrate. , Between the magnetic layer and the non-magnetic underlayer, h
The product (BsML) of the saturation magnetic flux density (BsML) and the magnetic layer thickness (tML) of the Co-based alloy which has the intermediate layer (IL) made of the Co-based alloy having the cp structure and which constitutes the magnetic layer.
The ratio of the product (BsIL · tIL) of the saturation magnetic flux density (BsIL) of the Co-based alloy constituting the intermediate layer to the intermediate layer thickness (tIL) with respect to tML) R = (BsIL · tIL) / (BsML · tML) ) Is 0.2 or less, the magnetic recording medium.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the non-magnetic substrate is usually made of Ni formed by electroless plating.
An aluminum alloy plate or a glass substrate provided with a -P layer is used, but in addition, a ceramic substrate, a carbon substrate, Si
Any non-magnetic substrate such as a substrate and various resin substrates can be used.

As the non-magnetic underlayer containing Cr as a main component formed on such a non-magnetic substrate, elements other than Cr,
For example, one kind or two kinds or more of Si, Ti, V, Mo, W and the like may be contained in the range of about 30 atomic% or less. The thickness of this non-magnetic underlayer is usually 100 to 20.
A range of 00Å, preferably 200Å or more is adopted.
If the underlayer is too thin, it will cause a large decrease in coercive force.

The Co-based alloy intermediate layer formed on such an underlayer has a close-packed hexagonal (hcp) crystal structure and the saturation of the Co-based alloy magnetic layer formed on this intermediate layer. Magnetic flux density (BsML) and Co-based alloy magnetic layer film thickness (t
ML) product BsML · tML, product BsI of the saturation magnetic flux density (BsIL) of the intermediate layer and the intermediate layer film thickness (tIL)
The L / tIL ratio is 0.2 or less, that is, it is a nonmagnetic or weakly magnetic intermediate layer satisfying the following formula (I). R = (BsML * tML) / (BsIL * tIL) <= 0.2 (I)

The product Bs · t of the saturation magnetic flux density Bs and the film thickness t represents the amount of saturation magnetization per unit area of the magnetic layer, and the value of Bs · t (BsIL · tI) in the intermediate layer of the present invention.
L is the value of Bs · t of the Co-based alloy magnetic layer (BsML ·
tML) is 20% or less, preferably 10% or less, and more preferably 0. If the ratio R of the two exceeds 0.2, the magnetic properties are deteriorated, such as a decrease in coercive force.

In the present invention, the provision of the intermediate layer means that C
The main purpose is to improve the characteristics of the initial growth layer of the o-based alloy magnetic layer. Therefore, it is desirable that the intermediate layer itself does not magnetically operate. The saturation magnetic flux density of the intermediate layer is set to such a small value as to satisfy the above formula (I), especially 0 Ga.
By setting uss (R = 0), the magnetic influence of the intermediate layer on the magnetic recording medium can be completely eliminated.

The material for the intermediate layer in the present invention is Cr, T
at least one of a, Ti, W, V, Mo and Si and Co
Alloys with are preferred. The content of these elements M in the intermediate layer material may be appropriately selected and is not particularly limited.
It is about 20 to 50 atom%. Further, in this case, a part of Co can be replaced with a magnetic element such as Ni. At this time, the intermediate layer is preferably non-magnetic, and for example, C
In the o-Cr based intermediate layer, the content of Cr is 34 to 45.
Atomic% means that the saturation magnetic flux density is 0 and the crystal is h
It is preferable because it has a cp structure.

The material alloy for the intermediate layer may contain other elements such as Ge, Cu, Zn, nitrogen, oxygen and hydrogen, as long as the performance as the intermediate layer is not impaired, as long as it is about several atomic% or less. . Further, other elements may be added to adjust the crystal lattice constant with the Co-based alloy magnetic layer. The thickness of such an intermediate layer is 10 to 100.
It is preferably 0Å, particularly 50 to 500Å.

As the Co-based alloy for the Co-based alloy magnetic layer formed on such an intermediate layer, CoCr-based alloy and Co-based alloy are usually used.
NiCr-based, CoPt-based alloys or the like are used, and these may further contain elements such as Ni, Cr, Pt, Ta, and B. Specific Co-based alloys for the Co-based alloy magnetic layer include CoCrTa alloys, CoNiCrBTa alloys, and Co.
PtCrTa alloy is mentioned. The thickness of the magnetic layer is not particularly limited, but it is usually formed to a thickness of 100 to 800 Å.

Such a magnetic recording medium of the present invention is manufactured by sequentially forming an underlayer, an intermediate layer and a magnetic layer on a non-magnetic substrate. At that time, the film is exposed to the atmosphere during the film formation. Instead, it is desirable to continuously and sequentially form films in a vacuum atmosphere.

The film forming method may be either a direct current or a high frequency magnetron sputtering method, and there are no particular restrictions on the sputtering conditions during film forming, and the bias voltage, substrate temperature, sputtering gas pressure, vacuum degree, etc. It is appropriately determined depending on the sputtering material. Normally, the bias voltage (absolute value) is 50 to 500 V, the substrate temperature is room temperature to 300 ° C., and the sputtering gas pressure is 1 × 10 −3 to 20 × 10 −3 Tor.
r, the degree of vacuum is 1 × 10 −6 Torr or less.
The magnetic recording medium of the present invention has a laminated structure in which the same intermediate layer and magnetic layer are further provided on the Co-based alloy magnetic layer as long as the above-mentioned combination of the intermediate layer and the Co-based alloy magnetic layer is satisfied. It may be.

That is, the magnetic recording medium of the present invention is characterized in that a Co-based non-magnetic (or weakly magnetic) intermediate layer is provided between the magnetic layer as the recording layer and the underlayer. For example, a non-magnetic substrate. A metal coating layer between the underlayer and the underlayer, a magnetic layer having a laminated structure of two or more Co alloy layers, a nonmagnetic intermediate layer provided on the magnetic layer, or a magnetic layer. In addition, if necessary, a protective layer of carbonaceous material and / or a lubricating layer made of a lubricant usually used may be formed.

[0019]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless it exceeds the gist. As shown in Tables 1 to 8, Examples and Comparative Examples were carried out under various conditions. In the present invention, the residual magnetic flux density (Br), the saturation magnetic flux density (Bs) and the coercive force (Hc) are VSM.
(Vibration Sample Magnetometer: VSM-3S type manufactured by Toei Industry Co., Ltd.) MH loop (hyster
The value was calculated based on the (esis loop). The conditions at the time of measurement are as follows. Maximum applied magnetic field 5000 (Oe) Sample size (length x width) 8 mm x 8 mm The film composition of the magnetic layer was analyzed by fluorescent X-ray analysis.

Examples 1 to 19 and Comparative Examples 1 to 4 (Examples 1 to 5) A nonmagnetic Ni-P layer having a thickness of 25 μm is formed on the surface of an aluminum alloy disk substrate having an inner diameter of 25 mm and an outer diameter of 95 mm by electroless plating. A film was formed, and the surface thereof was mirror-polished to obtain Ra (center line average roughness) of 20 to 30 Å.

This non-magnetic substrate is subjected to high frequency (13.56MH
z) Mounted on a magnetron sputtering device, 3 × 10 ^-6 T
After vacuum evacuation to orr, the substrate temperature is raised to 250 ° C., a partial pressure of argon is 5 × 10 ⁻³ Torr, and a bias voltage of DC-100 V is applied to the substrate, while the Cr underlayer is about 600 Å thick. It was formed into a film.

Then, after forming a CoCr film having a composition of Co63 atomic% -Cr37 atomic% to a thickness of 100 Å as an intermediate layer, Co80 atomic% -Cr14 atomic%-
By forming a magnetic film having a composition of Ta 6 atomic% in the range of 150 to 400Å, Br · t, which is the product of the residual magnetic flux density and the film thickness, can be obtained.
Of 60 to 180 gauss · μm were prepared (Examples 1 to 5).

The intermediate layer of Co63 atomic% -Cr37
The CoCr film having an atomic% composition is a non-magnetic material with Bs = 0Gauss and has an hcp structure. The relationship between Bs · t and Hc of the obtained sample is shown in FIG.

(Examples 6 to 9) Samples were prepared in the same manner as in Examples 1 to 5, except that Co 62 atom% -Cr 37 atom% -Ta 1 atom% was used as the intermediate layer. The relationship between Bs · t and Hc of the obtained sample is shown in FIG.

(Examples 10 to 14) Co6 as an intermediate layer
Samples were prepared in the same manner as in Examples 1 to 5 except that 0.5 atom% -Cr 36 atom% -Ti 3.5 atom% was used. The relationship between Bs · t and Hc of the obtained sample is shown in FIG.

(Examples 15 to 19) Co5 as an intermediate layer
Samples were prepared in the same manner as in Examples 1 to 5 except that 9.5 atom% -Cr36 atom% -V4.5 atom% was used. The relationship between Bs · t and Hc of the obtained sample is shown in FIG.

Comparative Examples 1 to 4 Samples were prepared under the same conditions as in Examples 1 to 5, except that the CoCr intermediate layer was not provided. The relationship between Bs · t and Hc of the obtained sample is shown in FIG.

[0028]

[Table 1]

As is clear from Table 1 and FIGS. 1 and 2, Hc of 400 was obtained by forming the Co type intermediate layer.
It can be seen that the temperature has risen by ~ 800 Oe.

Examples 20 to 23, Comparative Examples 5 to 8 With respect to each magnetic recording medium prepared in the same manner as Examples 1 to 5 or Comparative Examples 1 to 4, each magnetic recording medium was further formed on the magnetic layer with a thickness of 150 Å. A C (carbon) protective film was formed by a sputtering method, and an F (fluorine) -based lubricant was applied thereon to a thickness of about 30Å, and the electromagnetic conversion characteristics of each of the obtained magnetic recording media were measured. .

The electromagnetic conversion characteristics were measured by using an MR (magnetoresistive effect) head for a hard disk. The specifications of the head used and the measurement conditions are shown below. Head flying height 750Å Recording gap length 0.78 μm Playback shield width 0.22 μm Playback track width 4.2 μm Disc rotation speed 3,600 rpm Measuring radius 23 mm Recording frequency 20.1 MHz

Table 2 shows the measurement results of the electromagnetic conversion characteristics. FIG. 3 shows the relationship between the reproduction output and the S / N ratio of the magnetic recording medium, and FIG. 4 shows the relationship between the reproduction output and the half-value width (PW5) of the isolated reproduction waveform.
0) and the relationship with each.

[0033]

[Table 2]

From Table 2, FIG. 3 and FIG. 4, from CoCr
It is recognized that the magnetic recording medium provided with the intermediate layer is superior in both S / N characteristics and resolution.

Examples 24 to 28, Comparative Examples 9 to 10 (Examples 24 to 28) Similar to Examples 1 to 5 except that the Cr content of the CoCr intermediate layer was changed from about 29 atom% to 44 atom%. Then, a sample was prepared.

(Comparative Example 9) The procedure of Examples 1 to 5 was repeated except that the Cr content of the CoCr intermediate layer was changed to 24 atomic%.
A sample was prepared.

(Comparative Example 10) A sample was prepared in the same manner as in Examples 1 to 5, except that the Cr content in the CoCr intermediate layer was 54 atomic%. The Co-based intermediate layers used in each example except Comparative Example 10 have an hcp structure. Also,
The Bs (ML) of Co (80) Cr (14) Ta (6) was 5,500 (Gauss).

For the samples obtained in Examples 24 to 28 and Comparative Examples 9 and 10, the relationship between the Cr content of the CoCr intermediate layer and the coercive force Hc is shown in FIG. 5, and the Cr content of the CoCr intermediate layer and saturation. FIG. 6 shows the relationship between the magnetic flux density and the product Bs · t of the film thickness.

[0039]

[Table 3]

As is clear from Table 3 and FIGS. 5 and 6, it has an hcp structure and has a Bs.t (ML) /Bs.t (IL) of 0.20.
In the range of less than 0, especially less than 0.015, a remarkable effect of increasing the coercive force Hc is obtained. Also, this condition is Co
It can also be seen that in the Cr alloy, the Cr content is in the range of 27 to 52 atomic%, and particularly the effect is high in the Cr content of 34 to 47 atomic%.

Here, only in Comparative Example 10, CoCr
The intermediate layer does not have an hcp structure, and it is clear that it is important in the present invention that the intermediate layer has an hcp structure. Further, as is clear from Table 3, the CoCr intermediate layer is non-magnetic (Bs = 0) particularly in Examples 27 and 28 having high coercive force, so that the intermediate layer is preferably non-magnetic.

Examples 29 to 34, Comparative Examples 11 to 15 (Examples 29 to 34) Under the manufacturing conditions of Examples 1 to 5, the magnetic layer was made of Co70 atomic% -Cr21 atomic% -Pt9.
A sample was prepared in the same manner except that the CoCrPt magnetic layer having a composition of atomic% was changed, and the other conditions were changed.

(Comparative Examples 11 to 15) Samples were prepared under exactly the same conditions as described above except that the CoCr intermediate layer was not provided. Table 4 shows the constitution, coercive force, and manufacturing conditions of each sample, and FIG. 7 shows the relationship between the coercive force Hc and Bs · t.

[0044]

[Table 4]

From Table 1 and FIG. 7, it is clear that the effect of the Co type intermediate layer can be obtained even if the magnetic layer does not contain Ta.

Examples 35 to 37, Comparative Examples 16 to 18 (Examples 35 to 37) Under the manufacturing conditions of Examples 1 to 5, the high frequency sputtering method was a DC sputtering method, the bias voltage was -100 V to -500 V, and The CoCr intermediate layer thickness was changed from 100Å to 50Å, and the CoCrTa magnetic layer was changed to C
o56.5 atomic% -Ni30 atomic% -Cr7.5 atomic%
-B3 atomic% -Ta3 atomic% composition CoNiCrBT
Samples were prepared in the same manner except that the magnetic film was changed to a.

(Comparative Examples 16 to 18) Samples were prepared under exactly the same conditions as described above except that the CoCr intermediate layer was not provided. Table 5 shows the constitution, coercive force and manufacturing conditions of each sample, and FIG. 8 shows the relationship between the coercive force Hc and Bs · t.

[0048]

[Table 5]

From Table 5 and FIG. 8, it is clear that the effect of the Co-based intermediate layer can be obtained even if the sputtering method, bias voltage, and type of magnetic layer are changed.

Examples 38 to 41, Comparative Examples 19 to 22 (Examples 38 to 41) Under the manufacturing conditions of Examples 1 to 5, the high frequency sputtering method was a DC sputtering method, the bias voltage was -100V to -300V, and Cr underlayer thickness 6
From 00Å to 850Å, CoCr intermediate layer thickness is 100Å
To 170 Å, the CoCrTa magnetic layer was further changed to a CoCrPtTa magnetic film having a composition of Co 80 atomic% -Cr 12 atomic% -Pt 6 atomic% -Ta 2 atomic%, and other conditions were similarly used to prepare samples.

(Comparative Examples 19 to 22) Further, samples were prepared under the same conditions as above except that the CoCr intermediate layer was not provided. Table 6 shows the constitution, characteristics and manufacturing conditions of these samples.

[0052]

[Table 6]

The relationship between the magnetic force Hc and Bs · t is shown in FIG. From Table 6 and FIG. 9, it is clear that the effects of the present invention can be obtained also in the Co-based alloy magnetic layer containing Pt.

Examples 42 to 45, Comparative Example 23 (Examples 42 to 45) Under the manufacturing conditions of Examples 1 to 5, the magnetic layer was made of Co 78 atomic% -Cr17 having a thickness of 250 Å.
Atomic% -Ta5 atomic% was changed, and the other conditions were the same, and the thickness of the CoCr intermediate layer was 50Å to 50%.
A sample was prepared by changing it to 0Å.

(Comparative Example 23) A sample was prepared under exactly the same conditions as described above except that the CoCr intermediate layer was not provided. Table 7 shows the constitutions, characteristics and manufacturing conditions of these samples, and the coercive force Hc and Bs · t of each obtained magnetic recording medium.
The relationship with is shown in FIG.

[0056]

[Table 7]

It can be seen from Table 7 and FIG. 10 that the coercive force tends to decrease as the thickness of the intermediate layer increases.
It seems that an appropriate thickness of the intermediate layer is 500 Å or less.

Examples 46 to 49, Comparative Examples 24 to 26 (Examples 46 to 49) Under the manufacturing conditions of Examples 42 to 45, the thickness of the CoCr intermediate layer was 100 Å, and the other conditions were the same. Chromium underlayer thickness is 100-6
Samples having a variation of 00Å were prepared.

(Comparative Examples 24 to 26) Further, samples were prepared under exactly the same conditions as described above, except that the CoCr intermediate layer was not provided. Table 8 shows the constitution, characteristics and manufacturing conditions of these samples, and the coercive force Hc and B of each obtained magnetic recording medium.
The relationship with s · t is shown in FIG. 11.

[0060]

[Table 8]

It can be seen from Table 8 and FIG. 11 that the coercive force tends to decrease as the thickness of the intermediate layer increases.
It seems that 1000 liters or less is suitable for the thickness of the intermediate layer.

As described above, according to the magnetic recording medium of the present invention, a magnetic recording medium exhibiting a remarkably high coercive force and excellent electromagnetic conversion characteristics as compared with the conventional magnetic recording medium is provided, which is extremely suitable for high density recording. To be done.

[0063]

According to the present invention, C having an hcp structure
By providing an o-based non-magnetic or weakly magnetic intermediate layer, the magnetic effect of the intermediate layer is completely eliminated or significantly reduced, and the characteristics of the initial growth layer of the Co-based alloy magnetic layer to be the recording layer are improved. The coercive force and electromagnetic conversion characteristics of the magnetic recording medium are significantly improved.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between a product Bs · t of a saturation magnetic flux density and a film thickness and a coercive force Hc obtained in Examples 1 to 5 and Comparative Examples 1 to 4.

FIG. 2 is obtained in Examples 6 to 19 and Comparative Examples 5 to 7,
6 is a graph showing the relationship between the product Bs · t of the saturation magnetic flux density and the film thickness and the coercive force Hc.

FIG. 3 is a graph showing the relationship between reproduction output and S / N ratio obtained in Examples 11 to 14 and Comparative Examples 8 to 11.

FIG. 4 is a graph showing the relationship between the reproduction output and the half-value width PW50 of the isolated reproduction waveform obtained in Examples 11 to 14 and Comparative Examples 8 to 11.

5 is a graph showing the relationship between the Cr content and the coercive force Hc of the CoCr intermediate layers obtained in Examples 24 to 28 and Comparative Examples 9 and 10. FIG.

FIG. 6 is a graph showing the relationship between the Cr content of CoCr intermediate layers and the product Bs · t of the saturation magnetic flux density and the film thickness obtained in Examples 24 to 28 and Comparative Examples 9 and 10.

FIG. 7 is a graph showing the relationship between the product Bs · t of the saturation magnetic flux density and the film thickness and the coercive force Hc obtained in Examples 29 to 34 and Comparative Examples 11 to 15.

FIG. 8 is a graph showing the relationship between the product Bs · t of the saturation magnetic flux density and the film thickness and the coercive force Hc obtained in Examples 35 to 37 and Comparative Examples 16 to 18.

FIG. 9 is a graph showing the relationship between the product Bs · t of the saturation magnetic flux density and the film thickness and the coercive force Hc obtained in Examples 38 to 41 and Comparative Examples 19 to 22.

10 is a graph showing the relationship between CoCr intermediate layer thickness and coercive force Hc obtained in Examples 42 to 45 and Comparative Example 23. FIG.

FIG. 11 is a graph showing the relationship between the Cr underlayer thickness and the coercive force Hc obtained in Examples 46 to 49 and Comparative Examples 24 to 26.

Claims (10)

[Claims] 1. A non-magnetic substrate and a Co-based alloy magnetic layer (M
L) and a non-magnetic underlayer containing Cr as a main component between the magnetic layer and the substrate, wherein a Co-based alloy having an hcp structure is provided between the magnetic layer and the non-magnetic underlayer. The intermediate layer (IL) is formed, and the intermediate layer is formed with respect to the product (BsML · tML) of the saturation magnetic flux density (BsML) of the Co-based alloy forming the magnetic layer and the magnetic layer film thickness (tML). The product of the saturation magnetic flux density (BsIL) of the Co-based alloy and the film thickness of the intermediate layer (tIL) (BsIL ·
A magnetic recording medium characterized in that the ratio R = (BsIL · tIL) / (BsML · tML) of tIL) is 0.2 or less. 2. The intermediate layer is a Co-M alloy thin film layer (where M is one or more elements selected from the group consisting of Cr, Ti, W, V, Mo and Si). The magnetic recording medium according to claim 1, which is characterized in that: 3. M is Cr and Cr content is 27-5.
The magnetic recording medium according to claim 2, wherein the content is 2 atomic%. 4. The magnetic recording medium according to claim 1, wherein the intermediate layer has a thickness of 10 to 1000 Å. 5. The underlayer has a thickness of 100 to 1000Å
The magnetic recording medium according to claim 1, wherein 6. The magnetic recording medium according to claim 1, wherein the non-magnetic underlayer, the intermediate layer, and the magnetic layer are sequentially deposited in a vacuum atmosphere without being exposed to the air. 7. The Co-based alloy magnetic layer is CoCr-based or Co-based.
A NiCr-based or CoPt-based alloy magnetic layer.
The magnetic recording medium described. 8. The magnetic recording medium according to claim 1, further comprising a metal coating layer between the non-magnetic substrate and the underlayer. 9. The magnetic layer has a multi-layer structure.
The magnetic recording medium described. 10. The magnetic recording medium according to claim 1, further comprising a carbonaceous protective layer and / or a fluorine-based lubricating layer on the magnetic layer.