JPS62150524A - 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. 0.5-5at% Nd 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 layer 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 with the same sputtering vessel immediately after the formation of the layer 3. The Co-30at%Ni alloy contg. 2.8at% Nd 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 [Field of the Invention] 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, magnetic recording media such as magnetic disks used in magnetic recording devices have tended to have higher and higher recording densities, and with this trend, the thickness of the magnetic layer of magnetic recording media has been reduced from the conventional process of about 1 μm to less than 0.1 μm. <C7. 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. In addition, the magnetic layer of conventional iron oxide such as r-Fe 203 has a small magnetic property, especially a residual magnetic flux density, and a low output. Magnetic thin films of alloys such as cobalt-nickel (Ni) alloys have come into use. The Ni content of this alloy ranges from 20 to 30a.
It is known that t% is good.

FIG. 5 shows a cross-sectional view of the structure of a disk-shaped magnetic recording medium provided with a magnetic layer of, for example, a Co--Ni alloy magnetic thin film.

The magnetic recording medium shown in FIG. 5 has a non-magnetic base layer 2 on an alloy substrate 1.
A magnetic layer 4 of a Co--Ni alloy thin film is coated on the non-magnetic base layer 2 with a non-magnetic metal underlayer 3a interposed therebetween.
7, a protective layer 5a is formed on the magnetic layer la, and a lubricating layer 5b is formed thereon.

Aluminum alloy is often used for the alloy substrate IK 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 non-magnetic base layer 2 is preferably one obtained by electroless plating of a nickel-phosphorus (Ni-P) alloy, or one obtained by alumite treatment of the substrate 1. Both require a certain hardness, and the surface is A mirror finish is achieved by mechanical polishing. The non-magnetic metal underlayer i3a is usually mainly composed of chromium (Cr).
) etc. are formed by sputtering or the like to a film thickness of about 3000'A.

As magnetic N4a 7, Co -20・-30at%N
Co-Ni alloy thin films are effective in that magnetic recording media formed by sputtering exhibit good magnetic properties, but as further research has progressed on this Co-Ni alloy thin film, it has become clear that the initial magnetic properties are not excellent. However, due to the insufficient corrosion resistance of the thin magnetic layer itself, it was found that depending on the environment in which the magnetic recording medium is used, the magnetic properties may eventually deteriorate17.As a result of intensive research, the present inventors have found that C020 containing neodymium (Nd) has overcome the problems of magnetic properties and corrosion resistance, which were considered to be in a contradictory relationship.
It has been discovered that a ~30 at% Ni alloy has both magnetic properties and corrosion resistance in the magnetic layers 4a and t2, and this magnetic recording medium has been proposed by the same applicant.

On the magnetic layer 4a, C [or Cr oxide (Cr2
A protective layer 5a such as 03) and a lubricating layer 5b such as carbon or silicon dioxide (5iOz) are successively provided by sputtering. Depending on the medium, @
j @ 5 Don't make it a two-way between a and the lubricating layer 5b (
In some cases, a thin film of carbon or 5i02 is formed as a purulent lubricant layer, but a Cr or Cr oxide layer is provided in consideration of the corrosion resistance of the magnetic layer 4.

Here, the nonmagnetic metal underlayer 3a 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 is in a region where the coercive force of the magnetic layer 4a is saturated as the 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.
After forming a Co-Ni alloy thin film containing d by sputtering, a protective layer 5a such as Cri or Cr2O3 and a lubricating layer 5b such as carbon or 8102 are continuously coated by sputtering.
Since 4a has good magnetic properties and corrosion resistance, and the protective layer 5a is provided, the -)91 corrosion resistance is enhanced and excellent.

Based on the above, this magnetic recording medium is expected to have the effect of the gorge layer 5a, stably maintain magnetic properties, and retain the underlying layer 1.
There is a possibility that the sputtering time can be shortened by making the layer 3a as thin as possible. Therefore, Cr, which conventionally formed the base layer 3a with a thickness of about 3000
Instead, it is necessary to select a material for an underlayer with an even thinner film thickness, and to increase the Nd content added to the magnetic layer Co-Ni alloy that exhibits optimal magnetic properties in combination with this underlayer. By determining the range of , it is possible to obtain a magnetic recording medium with high manufacturing efficiency and good magnetic properties and corrosion resistance.

[Object of the Invention] The present invention has been made in view of the above points, and its object is to provide a nonmagnetic metal underlayer and a Co-Ni alloy thin film magnetic layer containing Nd on a nonmagnetic base coated on a substrate.

The protective layer and lubricant layer are sputtered and laminated in this order.
7, 1t under thin non-magnetic metal! ! Increase and appropriate amount of N
An object of the present invention is to provide a magnetic recording medium having good magnetic properties and corrosion resistance in combination with a Co--Ni alloy thin film magnetic layer containing d.

[The point of invention]

The present invention deals with N on an aluminum substrate in an inert gas atmosphere.
1-A base layer formed by continuous svantering on the P layer,
The base layer of the laminated thin film consisting of the magnetic layer, circulation dovetail and lubricating layer is a W film with a film thickness of approximately 500'h, and the magnetic layer is a NdO,5
This can be achieved by using a Co--Ni alloy group containing ~5 at%.

[Embodiments of the invention]

The present invention will be explained below based on examples.

FIG. 1 shows a cross section of a main part of a magnetic recording medium obtained according to the present invention, and parts common to those in FIG. 5 are denoted by the same reference numerals. The basic structure of FIG. 1 is the same as that of FIG. 5, but the difference between FIG. 1 and FIG. The point is that the Co--Ni alloy has a Nd content that provides good magnetic properties.

First, as the non-magnetic alloy substrate 1, a disc-shaped aluminum plate finished with sufficiently small waviness, that is, a surface of 20ρ or less in both the circumferential and radial directions, is used by lathe processing and pressure annealing. 'About 3 minutes of drunken menki
The plating film is coated to a thickness of 0 μm and has an average surface roughness of 0.
．． The non-magnetic substrate 2 is formed by performing mirror finishing to a thickness of 0.2 μm and a thickness of 15 μm. Next, a nonmagnetic metal underlayer 3 is formed on the nonmagnetic substrate 2 by sputtering W in the present invention, but the thickness of the underlayer 3 affects the magnetic properties of the magnetic layer 4 as described above. To find out how thin it can be, the thickness was varied from 0.05 μm to 0.3 μm at intervals of 0.1 μm. Forming the W base layer 3,
Immediately thereafter, a magnetic layer 4 with a thickness of approximately 500K was formed on the W underlayer 3 by sputtering in the same sputtering bath. N is used as the magnetic layer 4 to determine the thickness of the W film.
A Co-30 at% Ni alloy containing 2.8 at% of d 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 FIG. 2, the horizontal axis shows the thickness of the W film scaled at 0.05 μm intervals, and the vertical axis shows the Hc of the magnetic layer 4. Two other comparative examples are also shown in FIG. The effectiveness of the present invention is clearly demonstrated by comparing the present invention with the conventional example. The manufacturing method of the magnetic recording medium of Comparative Example 1 was the same as that of this example, except that the magnetic layer was a thin film made of Co alone, and in Comparative Example 2, the magnetic layer was similarly made of Co-30at%Ni. Thin film and L Nd
It is not added.

From FIG. 2, when W is used as the base Ffi 3 of the present invention, the Co-Ni alloy of the magnetic layer 4 contains Nd.
It can be seen that the effect of increasing He in the magnetic layer 4 is remarkable, and moreover, when the W film thickness becomes approximately 0.05 μm or more, Hc reaches saturation at a large value. This means that Co-30at%
A Ni-2,8at%Nd alloy magnetic film is used as the magnetic layer 4, and W is used as the magnetic layer 4.
When used in combination with base layer 3, the thickness of the W film is approximately 0.
．． This means that it is possible to reduce the thickness to 0.5 μm. On the other hand, in Comparative Examples 1 and 2, the W film thickness was increased [
7, the Hc of the magnetic layer is not too thick (and the W underlayer 3
The effect of the combination with the Co--Ni alloy (magnetic) fi 4 containing Nd is clear from FIG.

Note that if the magnetic layer 4 is left in the sputtering bath for too long or exposed to the atmosphere before sputtering the magnetic layer 4 following the base layer 3, the effect of the base layer 3 will not be exhibited and the magnetic layer will deteriorate. The large coercive force required by 44 cannot be obtained. For example, if the underlayer 3 is formed and then exposed to the atmosphere and the magnetic layer 4 is formed thereon, the coercive force of the magnetic layer 4 will be violet 2000 et. The same result will occur even if the magnetic layer 4 is left in the sputtering bath 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'A,
In order to determine the amount of NdO added to the Co-Ni alloy magnetic layer provided thereon, the Co-30 at%
The Nd content of the N1-Nd alloy was varied in the range of O to 15 at%, and the magnetic properties were investigated. The results are shown in Figure 3 (
a) to (d) K is shown. FIG. 3 is a diagram in which the horizontal axis represents the Nd content, and the vertical axis represents the magnetic properties, plotting the average value of three points. In other words, Fig. 3(a) shows the coercive force,
Figure 3(b) shows the coercive force squareness ratio (S"), and Figure 3(c) shows the residual magnetic flux density and other conditions being the same. lol
, total gas pressure4. OX 1O-2 Torr, the substrate temperature is room temperature, and the W film thickness of the base layer 3 is all 5 as described above.
It was set to 0 Å.

As can be seen from FIGS. 3(a) to 3(d), N of the magnetic layer 4
The magnetic property that changes the most with respect to the d content is Hc in the figure (a), and the range of Nd content that can be obtained is 9000e or more, which is effective as a magnetic recording medium, is 0.5 to 5 at%, and 10000e or more. The most preferable range to exceed is 1.5
~4.5 at%. In this range of Nd content,
When I looked at it, I found that (S” in figure b1, Br-aw in figure (c)
(d) In both cases, Bs-δ tends to decrease as the Nd content increases. However, this degree of decrease does not pose any particular problem in terms of magnetic properties.

In this way, the magnetic recording medium of the present invention uses a W film as the underlayer 3 and has a film thickness of up to 500 hours. %
Although good magnetic properties can be maintained by forming a Nd alloy thin film, Cr or Cr2O3
Maintenance MJm5g and lubrication such as carbon or 5i02/
M5b is coated to a film thickness of 500 Å and has excellent corrosion resistance.

Figure 4 shows 1 exposed to an atmosphere with a temperature of 40°C and a relative humidity of 80%.
7. The magnetic recording medium of the present invention, that is, the underlayer 3 is a W film and the magnetic layer 4 is Co-30at%Ni-2, 8at%Nd.
FIG. 2 is a diagram showing changes in the number of errors with respect to an unused period when a recording device having the configuration shown in FIG. 1 is used. In the case of FIG. 4, Comparative Example 1 and Comparative Example 2, which are the same as those in FIG. 2, are also shown. As shown in FIG. 4, the number of errors in the magnetic recording medium of the present invention is only 7 after being left for 12 weeks, whereas the number of errors in the comparative example 1 is only 7. In Comparative Example 2, the number of errors increases rapidly within a short period of time, making it unusable. This means that the magnetic properties of the entire magnetic layer undergo large changes over a relatively long period of time depending on the environmental conditions. Even if there is no magnetic layer, when exposed to moisture, etc., conventional magnetic fM is corroded sequentially from minute local areas on the surface and deterioration progresses, whereas the present invention, which has a magnetic layer containing an appropriate amount of Nd, It can be seen from FIG. 84 that the magnetic recording medium has excellent corrosion resistance. Furthermore, the fourth
Although not shown in the figure, similar results can be obtained for any Co--Ni alloy magnetic layer containing Nd in the range of 0.5 to 5 at%.

Furthermore, as a result of conducting a C8S test by incorporating the magnetic recording medium of the present invention into a magnetic recording medium, it was found that even after 20,000 contact starts and stops, no scratches occurred on the surface of the recording medium, and the playback output remained unchanged. It was demonstrated that it had sufficient durability with almost no deterioration.

As explained above, the magnetic recording body of the present invention uses a thin W film as a non-magnetic metal underlayer to shorten the time for stripping and unloading, and also exhibits good magnetic properties compatible with the W film. It can be said that it has a magnetic layer of the composition [7] and has excellent corrosion resistance.

〔Effect of the invention〕

In order to increase the recording density of magnetic recording media such as magnetic tape, the thickness of the magnetic layer is reduced to improve the magnetic properties.
A Co-Ni alloy thin film formed by sputtering has come to be used, but on the other hand, the Co-Ni alloy resuscitator layer has the disadvantage that its corrosion resistance in the usage environment is inferior to that of, for example, an iron oxide film. Many researchers have determined the third element and its addition amount range σ to the Co-Ni alloy that can impart corrosion resistance while retaining magnetic properties, and have also added Cr to the magnetic layer.
As a result of repeated research into a material that can make the base layer thinner in conjunction with the behavior of the protective layer, the present invention has developed
As explained in , C containing 0.5 to 5 at% Nd
o-Ni'.

By using a thin gold film as the magnetic layer and a W film with a thin film thickness of approximately 500X as the underlayer, the second W underlayer acts effectively to increase the Hc of the magnetic layer, and at the same time The corrosion resistance of Co-Ni-0,
The combination of a magnetic layer with a composition of 5~Sat%Nd and a W underlayer solves the conventionally contradictory problems of magnetic properties and corrosion resistance all at once, allowing a single recording medium to have these two properties. Moreover, since the base layer and the W film were used, which can reduce the film thickness to approximately 500 Å, manufacturing efficiency was achieved by shortening the spatter time. E 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, being stable, and having a long life.

[Brief explanation of drawings]

) Figure 1 shows a cross-section of the configuration of the magnetic recording medium of the present invention. Figure 2 shows the Hc of the magnetic layer relative to the thickness of the underlayer.
Q) A diagram showing the change in r. Figure 3 is a diagram showing the relationship between the Nd content of the magnetic layer and the magnetism. Figure 4 is a diagram showing the relationship between the Nd content of the magnetic layer and the magnetic properties. Figure 4 is a diagram showing the temperature at 40°C. r Exposure to an atmosphere of 80% relative humidity 1. FIG. 5 is a diagram showing the relationship between the storage period of a magnetic recording medium and the number of errors, and FIG. 5 is a cross-sectional view of the main part of a conventional magnetic recording medium. l...Alloy substrate, 2...Nonmagnetic base layer, 3, 3a.
...Nonmagnetic metal base layer, 4, 4a...Magnetic layer, 5a.
...Protective layer, 5b...Lubricating layer. 7・′. , -9-8, Nishiro bud 1 Fig. 1 W IL'4 (/-1m) Fig. 2 (α) (b) (c) (d) Fig. 3 Fig. 4 h Fig. 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. . A magnetic recording medium, wherein the magnetic layer is made of a Co--Ni alloy containing 0.5 to 5 at% of Nd, and the nonmagnetic metal underlayer is made of W. 2) A magnetic recording medium according to claim 1, wherein the magnetic layer has an Nd content of 1.5 to 4.5 at%. 3) A magnetic recording medium according to claim 1 or 2, characterized in that the W film thickness is approximately 500 Å.