JPS62150521A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve magnetic characteristics and corrosion resistance by consisting a magnetic layer of a Co-Ni alloy contg. 2.5-11.5at% La and consisting of a nonmagnetic metallic underlying layer of W. CONSTITUTION:A nonmagnetic substrate 2 is formed by using a disk-shaped aluminum plate finished to <=20mum surface in both circumferential and radial directions, forming an electroless plating film of the Ni-P alloy thereon to about 30mum thickness and finishing the plating film to a specular surface up to 0.02mum average surface roughness and 15mum thickness. The nonmagnetic metallic underlying layr 3 is then formed on the substrate 2 by sputtering W. The magnetic layer 4 is formed by sputtering onto the W underlying layer 3 to about 500Angstrom thickness within the same sputtering vessel immediately after the formation of the layer 3. The Co-30at%Ni alloy contg. 5at% La is used as the magnetic layer to determine the thickness of the W film. The time for sputtering is thus shortened by using the thin W film for the nonmagnetic metal lic underlying layer and the magnetic layer made of the compsn. exhibiting the good magnetic characteristics is obtd. Excellent corrosion resistance is obtd. as well.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a magnetic recording medium such as a magnetic disk used in a magnetic recording device.

[Prior art and its problems]

In recent years, there has been a trend toward higher and higher recording densities in magnetic recording media such as magnetic disks used in magnetic recording devices. .Thin comb down to 1μm or less.

It is also necessary to increase the coercive force (Hc). For this reason, sputtering and plating methods, which can easily form a uniform thin film, are attracting attention as a manufacturing method for magnetic recording media, as they can easily form a uniform thin film, instead of the spin code method, which results in non-uniform magnetic layer thickness on the submicron order. Along with.

A conventional magnetic layer of iron oxide, e.g. r-Fe 203, is
Because of its magnetic properties, especially its small residual magnetic flux density and low output, a magnetic thin film of a cobalt (Co) alloy (for example, a cobalt-nickel (Ni) alloy) formed by sputtering is used as the magnetic layer. It became so. It is known that the Ni content range of this alloy is preferably 20 to 30 at%.

FIG. 5 shows a sectional view of the lower part of a disk-shaped magnetic recording medium including a magnetic layer of a Co--Ni alloy magnetic thin film, for example.

The magnetic recording medium shown in FIG. 5 has a non-magnetic base layer 2 on an alloy substrate 1.
A magnetic layer 4a of a CoJJi alloy thin film is further coated on the nonmagnetic substrate N2 via a nonmagnetic metal underlayer 3a, and a protective layer 5a is formed on the magnetic layer 4;I and a lubricating layer 5b is formed thereon. was formed.

Aluminum alloy is often used for the alloy substrate 1 of the magnetic recording medium constructed in this way, but plastic may also be used in some cases, and the substrate is finished to a predetermined surface roughness, parallelism, and flatness.

The nonmagnetic base layer 2 is preferably obtained by electroless plating of a nickel-phosphorus (Ni-P) alloy, or by alumite treatment of the substrate 1 itself. Both require a certain hardness, and the surface is mechanically coated. Polish to a mirror finish. The nonmagnetic metal underlayer 3a is usually made of chromium (Cr) or the like, and is formed to a thickness of about 3000 Å by sputtering or the like.

The magnetic layer 4a and the shite are made of Co-20~30;lt%N
C. is effective in that a magnetic recording medium in which an i-alloy thin film is formed by sputtering exhibits good magnetic properties.

-As research progressed on Ni alloy thin films, it was discovered that although the initial magnetic properties were excellent, the corrosion resistance of the thin magnetic layer itself was insufficient, and the magnetic properties could eventually deteriorate depending on the environment in which the magnetic recording medium was used. As a result of intensive research, the inventors of the present invention overcame the problem of magnetic properties and corrosion resistance, which had been considered to be in a contradictory relationship.

Co 20 to 30 at% including Uypn (La)
It has been discovered that Ni alloy has both magnetic properties and corrosion resistance as a magnetic J-4A, and this magnetic recording medium has been proposed by the same applicant.

Cr or Cr oxide (Cr20
A protective layer 5a such as 3) and a lubricating layer 5b such as carbon or silicon dioxide (8i02) are both successively provided by sputtering. Depending on the medium, protective layer 5
In some cases, a thin film of carbon or 8i0□ is formed as an fI lubricating layer without forming two layers, ie, a and a lubricating layer 5b, but the reason why a Cr or Cr oxide layer is provided is to improve the corrosion resistance of the magnetic layer 4. This is because they take into consideration the following.

Here, the nonmagnetic metal underlayer 38 will be described again.

The non-magnetic metal underlayer 3a is a Co-Ni alloy thin film magnetic layer 4a.
This has the effect of increasing the coercive force (Hc) of the magnetic layer 4a, and the coercive force of the magnetic layer 4a also changes depending on the thickness of the underlayer 3a. The underlayer 3a tends to saturate the coercive force of the magnetic layer 4a as its thickness increases, and the thickness of the underlayer 3a that saturates the coercive force varies greatly depending on the material. Further, as shown in FIG. 5, the above-mentioned La
A magnetic recording medium is constructed by forming a Co-Ni alloy thin film containing Crj or Cr2O3 by sputtering, and then successively sputtering a protective layer 5a such as Crj or Cr2O3 and a lubricating layer 5b such as carbon or SiO□. 4a has good magnetic customization and corrosion resistance, and the protective layer 5a
Therefore, this magnetic recording medium is expected to have the effect of the protective layer 5a, and the underlayer 3a is coated with the underlayer 3a while maintaining the magnetic properties stably. It has the potential to be made as thin as possible and to shorten sputtering time. Therefore, instead of Cr, etc., which conventionally formed the base layer 3a with a thickness of about 3000A, 7! Furthermore, we selected a material for a thinner underlayer, and determined the range of La content to be added to the magnetic layer Co-Ni alloy that exhibits optimal magnetic properties in combination with this underlayer. From Do K,
A magnetic recording medium with high manufacturing efficiency and good magnetic properties and corrosion resistance can be obtained.

[Purpose of the invention]

The present invention has been made in view of the above points.

The purpose is to coat a nonmagnetic substrate with a nonmagnetic metal underlayer and a Co-Ni alloy thin film magnetic layer containing La.

A protective layer and a lubricant layer are sputtered and laminated in this order, and it has good magnetic properties and corrosion resistance due to the combination of a particularly thin non-magnetic metal underlayer and a co-Ni alloy thin film magnetic layer containing an appropriate amount of La. The object of the present invention is to provide a magnetic recording medium that has the following characteristics.

[Key points of the invention]

The present invention deals with N on an aluminum substrate in an inert gas atmosphere.
1-A base layer formed by continuous sputtering on the P layer,
The base layer of the laminated thin film consisting of the magnetic layer, protective layer and lubricating layer is a W film with a film thickness of approximately 500^, and the peak layer is a W film with a thickness of La 2.5 to 1.
This can be achieved by using a Co--Ni alloy model containing 15at.

[Embodiments of the invention]

The present invention will be explained below based on examples.

FIG. 1 shows a cross section of the main part of a magnetic recording medium obtained according to the present invention, and the dust passage portions are designated by the same reference numerals as in FIG. 5. The basic configuration of FIG. 1 is the same as that of FIG. 5, but there are differences between FIG. 1 and FIG. 5.

The non-magnetic metal underlayer 3 is a W film, and the magnetic layer 4 is a C film with a La content that provides better magnetic properties than the W underlayer.
The point is that it is an o-Ni alloy.

First, as the non-magnetic alloy substrate 1, a disc-shaped aluminum plate finished with sufficiently small waviness, that is, 20 μm or less in both the circumferential and radial directions, is used by lathe processing and pressure annealing. Approximately 30 electrolytic plating
The plating film is coated to a thickness of μm and has an average surface roughness of 0.0.
The non-magnetic substrate 2 is formed by mirror finishing with a thickness of 2 .mu.m and a thickness of 15 .mu.m. Next, in the present invention, W is sputtered to form a non-magnetic metal base layer 3 on the non-magnetic substrate 2, but the thickness of the base layer 3 is as described above.
Since this affects the magnetic properties of
．． The thickness was varied up to 3 μm. Immediately after forming the W underlayer 3, a magnetic layer 4 was sputtered to a thickness of approximately 50 mm on the W underlayer 3 in the same sputtering tank. The magnetic layer 4 for determining the thickness of the W film contains 5 at% of La.
('o-3Qat%Ni alloy was used.

FIG. 2 is a diagram showing the change in Hc of the magnetic layer 4 with respect to the thickness of the W film provided as the underlayer 3. In Figure 2, the thickness of the W film is scaled on the horizontal axis at 0.05 μm intervals.

Although the vertical axis indicates Hc of the magnetic layer 4, two other comparative examples are also shown in FIG. 2, and the effectiveness of the present invention is clarified by comparing the present invention and the conventional example. The manufacturing method of the magnetic recording medium of Comparative Example 1 is the same as that of this example, except that the magnetic layer is a thin film made of CO alone, and in Comparative Example 2, the magnetic layer is similarly made of Co-3Qat%Ni. It is a thin film and does not contain La.

From FIG. 2, when W is used as the base layer 3 of the present invention,
The Co-Ni alloy of the magnetic layer 4 may contain La.

It can be seen that the effect of increasing the Hc of the magnetic layer 4 is remarkable, and moreover, when the W film thickness becomes approximately 0.05 μm or more, the Hc reaches saturation at a large value. This means that Co-3Qat%
When using a Ni-5at%La all-La film as the magnetic layer 4 in combination with the W underlayer 3, the thickness of the W film is #WY0.
This means that it is possible to reduce the thickness to 0.5 μm.

On the other hand, in Comparative Examples 1 and 2, even if the W film thickness was increased, the Hc of the magnetic layer did not increase so much, and the W underlayer N3 and L
It is clear from FIG. 2 that the effect of the combination with the Co--Ni alloy magnetic layer 4 containing a is clear. If the underlayer 3 is exposed to the atmosphere, the effect of the underlayer 3 cannot be exhibited, and the large coercive force required by the magnetic layer 4 cannot be obtained. For example, after forming the underlayer 3, the magnetic layer 4 is exposed to the atmosphere.
formed thereon, the coercive force of the magnetic layer 4 is only 20
00e L cannot be obtained. The same result occurs even when the magnetic layer 4 is left in the sputter curtain for a long time, so the magnetic layer 4 must be sputtered immediately after the underlayer 3 is formed.

Next, when the film thickness of the W underlayer 3 is constant at 500 people, La added to the co-Ni alloy magnetic layer provided thereon is
To determine the amount of Co-3Qat%N1 in the magnetic layer 4,
The magnetic properties of the -La alloys were investigated by changing the La content in the range of 0 to 15 at%. The results are shown in Figure 3(a)~
(d3 K is shown.) Figure 3 is a diagram in which the horizontal axis is the La content and the vertical axis is the magnetic property, and the average value of three points is plotted. In other words, Figure 3 (a) shows the coercive force, Figure 3 (
b) is the coercive force squareness ratio (Shu, Figure 3 (C) is the residual magnetic flux density (Br), all other conditions are the same, and both are RF sputtering equipment with an output of 500 W and a total gas pressure of 4. ．．
0X10-2 Torr, substrate temperature is room temperature, base layer 3
The film thickness of W in all cases was 500A as described above.

As can be seen from FIGS. 3(a) to 3(d), L of the magnetic layer 4
The magnetic property that changes the most with respect to a content is (a) Hc in the figure, and the range of La content that can be obtained at 9000e or higher, which is effective as a magnetic recording medium, is 2.5 to 11.5 at%.
, and the most preferable range exceeding 10,000e is 3.
It is 5 to 9 at%. Looking at the La content in this range, the values s in figure (b), Br and δ in figure (cj), and Bs and δ in figure (d) all tend to decrease as the La content increases. However, This degree of decline does not pose a particular problem in terms of magnetic properties.Thus, even if the magnetic recording medium of the present invention uses a W film as the underlayer 3 and the film thickness is reduced to 500, the thickness of the underlayer 3 can be reduced to 500. The magnetic layer 4 contains Co-3Qat%Ni-2,5~11.5a
Although good magnetic properties can be maintained by forming a t% La alloy thin film, Cr or Cr
A protective layer 5a of 2O3 and a lubricant layer 5b of carbon or Sr02 are formed by sputtering to a thickness of 500 mm, thereby providing excellent corrosion resistance.

FIG. 4 shows the magnetic recording medium of the present invention exposed to an atmosphere with a temperature of 409C and a relative humidity of 80C, that is, the underlayer 3 is a W film and the magnetic layer 4 is Co-30at%Ni-5at%L.
FIG. 2 is a diagram showing changes in the number of workpieces with respect to the neglect period when a recording device having the configuration shown in FIG. 1 is used as a recording device. In the case of FIG. 4, Comparative Example 1 and Comparative Example 2, which are the same as in FIG. 2, are also shown. As shown in FIG. 4, the magnetic recording medium of the present invention has only a small number of errors counted after being left for 12 weeks, whereas the magnetic recording medium of the comparative example 1. In Comparative Example 2, the number of errors increases rapidly within a short period of time, making it unusable. This means that even though the magnetic properties of the entire magnetic layer do not change significantly over a relatively long period of time depending on environmental conditions, conventional magnetic layers corrode sequentially starting from minute localized areas on the surface when exposed to moisture. On the other hand, it can be seen from FIG. 4 that the magnetic recording medium of the present invention having a magnetic layer containing an appropriate amount of La also has excellent corrosion resistance. Although not shown in FIG. 4, similar results can be obtained for any co-Ni alloy magnetic layer containing La in the range of 25 to 11.53 t%.

Furthermore, as a result of conducting a C8S test by incorporating the magnetic recording medium of the present invention into a magnetic recording device, no scratches occurred on the surface of the recording medium even after 20,000 contacts, starts, and stops, and the reproduction output hardly decreased. It has been demonstrated that it has sufficient durability without any damage.

As explained above, the magnetic recording medium of the present invention shortens the sputtering time by using a thin W film as a non-magnetic metal underlayer, and also has a magnetic layer having a composition that exhibits good magnetic properties corresponding to the W film. [Effects of the Invention] In order to increase the recording density of magnetic recording media such as magnetic disks, the thickness of the 1jIi layer is reduced to improve magnetic properties. In order to achieve this, Co-Ni alloy thin films formed by sputtering have come to be used, but on the other hand, Co-Ni alloy magnetic layers have the disadvantage that their corrosion resistance in the usage environment is inferior to, for example, iron oxide films. They determined the third element and the range of its addition to the Go-Ni alloy, which imparts corrosion resistance while retaining magnetic properties, and combined with the effect of the Cr protective layer provided on the magnetic layer, the underlayer As a result of repeated research on materials that can be made thinner, in the present invention, as explained in the examples, La is reduced to 2.5 to 11.5 at%.
By using a Co-Ni alloy thin film containing as a magnetic layer and a W film with a thickness reduced to approximately 500A as an underlayer,
The W underlayer acts effectively to increase the Hc of the magnetic layer, and at the same time improves the corrosion resistance of the magnetic layer itself.
A magnetic layer with a composition of −2,5 to 11,5 at% La and W
The combination with the underlayer solves the conventionally contradictory problems of magnetic properties and corrosion resistance, and makes it possible to combine these two characteristics into one recording medium. Since a W film whose film thickness can be reduced by approximately 50 times 1 is used, manufacturing efficiency is improved by shortening sputtering time. Therefore, the magnetic recording medium of the present invention has many advantages when used in a recording device, such as being able to provide sufficient output and stably maintain a long life.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the main part of the magnetic recording medium of the present invention, and FIG.
The figure is a diagram showing the change in He in the magnetic layer with respect to the thickness of the underlayer, Figure 3 is a diagram showing the relationship between the La content of the magnetic layer and magnetic properties, and Figure 4 is a diagram at a temperature of 40°C. A diagram showing the relationship between the storage period and the number of errors in a magnetic recording medium exposed to an atmosphere with a relative humidity of 80 degrees. FIG. 5 is a cross-sectional view of the main part of a conventional magnetic recording medium. 1... Alloy substrate, 2... Nonmagnetic body layer, 3, 3a
...Nonmagnetic metal underlayer, 4,4a...Magnetic layer, 5
a... Protective layer, 5b... Lubricating layer.・-Papa・・・・・,'J゛,-・, Fig. 1 0.1 0,2 0.3 W ring KC) Am) Fig. 2 (a) (b) Fig. 3, mlmgF, 8 (weeks) Figure 4 Figure 5 @

Claims (1)

[Claims] 1) A magnetic recording medium in which a nonmagnetic metal underlayer, a magnetic layer, a protective layer, and a lubricant layer are laminated in this order by successive sputtering on a nonmagnetic substrate that covers the main surface of a substrate. , the magnetic layer contains 2.5 to 11.5 at% of Co-N
1. A magnetic recording medium comprising an i alloy, wherein the nonmagnetic metal underlayer comprises W. 2) A magnetic recording medium according to claim 1, wherein the magnetic layer has a La content of 3.5 to 9 at%. 3) A magnetic recording medium according to claim 1 or 2, characterized in that the W film thickness is approximately 500 Å.