JPS62149024A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve corrosion resistance without spoiling the magnetic characteristics of a Co alloy by adding La to the Co-Ni alloy of a magnetic layer. CONSTITUTION:Electroless plating of an Ni-P alloy is coated on a nonmagnetic substrate 1 for which a disk-shaped aluminum plate is used to form a nonmagnetic base body 2. Cr is sputtered on the base body 2 to form a nonmagnetic metallic underlying layer 3 and in succession, the magnetic layer 4 consisting of the Co-Ni alloy contg. 0.5-12.5at% La is provided thereon within the same sputtering vessel. Then the underlying layer 3 acts effectively to improve the Hc of the magnetic layer 4 and at the same time, the corrosion resistance of the magnetic layer 4 itself is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field 71) 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, magnetic recording media such as magnetic disks used in magnetic recording devices are becoming more and more densely packed.
Accordingly, it is necessary to reduce the thickness of the magnetic layer of a magnetic recording medium from about 1 jqiV & the conventional approximately 1 μm to 0.1 μm or more, and to increase the coercive force (He). Therefore, in the manufacturing method of magnetic recording media, in the submicron order, instead of the spin code method in which the thickness of the magnetic layer is non-uniform, sputtering method or plating method, which is difficult to easily form a uniform thin film, is used. As well as attracting attention, conventional iron oxides such as 1-F
Ezes magnetic 1'lE't! For example, cobalt l- (Co
Magnetic thin films of cobalt-nickel (Ni) alloys, such as cobalt-nickel (Ni) alloys, have come into use. Size range H2 including N1
It is known that 0 to 3 oat X is good.

Figure 6 shows, for example, a Co-Ni alloy (Shigeru: ' also shows the magnetic properties of a thin film.
1 is a sectional view showing a main part configuration of a disk-shaped magnetic recording medium equipped with a disk-shaped magnetic recording medium.

The magnetic recording medium shown in FIG. 6 has a non-magnetic base layer 2 on an alloy substrate 1.
On this non-magnetic base layer 2, a magnetic layer 4a of a Co--Ni alloy thin film is further formed via a non-magnetic metal underlayer 3.
The J1 lubricating film 5 is coated on the magnetic layer 4a.

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.

Is the nonmagnetic base layer 2 free of nickel-phosphorus (Ni-P) alloy? ! It is preferable to use a screen-plated one or one obtained by alumite treatment of the substrate 1 itself. Both require a certain hardness, and the surface is mirror-finished by mechanical polishing and calendering. The nonmagnetic metal underlayer 3 is generally formed using chromium (Cr) by sputtering or the like. This base layer 3 is C
It has the effect of estimating the coercive force (Hc) of the o-Ni alloy thin film magnetic layer 4a, and the coercive force of the magnetic layer 4a also changes depending on the thickness of the underlayer 3. The underlayer 3 tends to saturate the coercive force of the magnetic primary layer 4a as the magnetic flux increases, and the thickness of the underlayer 3 that saturates the coercive force varies widely depending on the material. Therefore, when manufacturing a practical magnetic recording medium, the film thickness of the underlayer 3 should not be made too large by 1$, and the thin film formation time should be shortened to maintain an appropriate coercive force in the magnetic layer 4.
I am trying to give it to a. Magnetic layer 4a on base No. 3
After forming by sputtering, a moisturizing film 5 of carbon or silicon dioxide (SiO2) or the like is continuously coated.

A magnetic recording medium having a magnetic layer formed by sputtering a Co--Ni alloy thin film obtained as described above is effective in that it exhibits good magnetic properties. However, as further research progressed on this Co-Ni alloy thin film, it became clear that although its initial magnetic properties were excellent,
It has been found that because the thin film magnetic layer itself does not have sufficient corrosion resistance, the magnetic properties may eventually deteriorate depending on the environment in which it is used.

Various countermeasures against this problem have been attempted. One of them is that from the point of view of corrosion resistance, iron oxide is stable in the surrounding environment, so it is better to make a thin film of γ-Fe2O3 by sputtering, for example, but on the other hand, as mentioned above, iron oxide film is The magnetic properties, particularly the residual magnetic flux density, are low, and forming iron oxide as a thin film by sputtering requires complicated procedures such as sputtering conditions and heat treatment, which is undesirable because there are many hidden spots. The second countermeasure, for example, is to use a method that is often used in the field of metal materials to completely improve corrosion resistance by adding chromium (Cr) to CO-based alloys. Even if it is added, the corrosion resistance will improve, but on the other hand, it is not possible to avoid a low F of the magnetic special order. As a third measure, Co −
It seems to be effective to form a protective film on the surface of the Ni alloy thin film that can completely block out the effects of the surrounding environment, but there are issues with the lubricity with the magnetic head, the hardness and e-tightness required for the thin protective film. No protective film has yet been found that satisfies the requirements of preserving livability.

For these reasons, a magnetic layer formed by sputtering on a magnetic recording medium is expected to have a vaguely auxiliary effect, and is an excellent material that combines magnetic properties and corrosion resistance, which were previously considered to be contradictory. It is necessary to develop something new.

[Purpose of the invention]

The present invention has been made in view of the above points, and its purpose is to provide a magnetic recording medium in which a thin film magnetic layer is formed that has improved corrosion resistance without impairing the magnetic properties of a CO-based alloy. .

[Key points of the invention]

The present invention deals with N on an aluminum substrate in an inert gas atmosphere.
1-A do layer formed by continuous sputtering on the P layer,
This is achieved by forming a Co--Ni alloy magnetic thin film containing lanthanum (La) as a thin film magnetic layer consisting of a magnetic layer and a layer of lubrication.

[Embodiments of the invention]

Hereinafter, the F$ invention will be explained based on examples.

FIG. 1 is a cross-sectional view of the essential parts of the iia=;d recording medium obtained by the present invention, and the same reference numerals as in FIG. 61 are used to indicate the same parts. Figure @1 has the same basic configuration as Figure @6, but the difference between Figure 1 and Figure 6 is that the magnetic layer 4 has C.
o -Ni-La alloy thin film is used.

First, as the non-magnetic alloy substrate 1, a disk-shaped aluminum plate which has been lathe-processed and pressure-sintered and finished with sufficiently small waviness, that is, 20 μm or less in both the circumferential and radial directions, is used. The non-magnetic substrate 2 is formed by applying electroless plating of an alloy to a thickness of about 30 μm and finishing the plating film to an average surface roughness of 02 μm and a thickness of 15 μm. Next, Cr is sputtered to form a non-magnetic metal underlayer 3 on the non-magnetic substrate 2, but the thickness of the Cr film affects the magnetic properties of the magnetic III 4 as described above, so it is formed at intervals of 0.1 μm. The thickness was changed to .8 μm. After forming the underlayer 3, I [sequentially in the same sputtering bath as the magnetic layer 4, Co-
Underlayer 3 of 30 at% Ni-La alloy is sputtered.
A thickness of 50 OA was provided on top of the . In order to clarify the effect of adding La to this magnetic alloy thin film, films were prepared in which the La content was changed every 5 atX up to 15 at%. At this time, if the magnetic +44 is sputtered after the underlayer 3, if it is left in the sputtering chamber for too long or exposed to the atmosphere, the effect of the underlayer 3 will not be exhibited and the magnetic +44 will be sputtered. The large coercive force required by the magnetic field cannot be obtained. For example, if the underlayer 3 is formed and then the magnetic layer 4 is formed thereon by exposing it to the atmosphere, the coercive force of the magnetic layer 4 will be only 2000e. This is the same result when left in the sputter tank for a long time.
After forming the underlayer 3, the magnetic layer 4 must be sputtered immediately. Finally, carbon was sputtered to form a surface protective lubricant film 5 to a thickness of 500 Å, thereby producing this magnetic recording medium.

Next, various properties of the magnetic recording medium obtained as described above will be described.

FIGS. 2(a) to 2(d) show Co − provided as the magnetic layer 4.
It is a diagram showing the relationship with magnetic properties when changing the La content of a 30at% Ni-La alloy, in which the horizontal axis is plotted as La content at 5at% intervals, and the vertical axis is plotted as magnetic properties. It is something. In other words, Fig. 2 (a) shows the coercive force, Fig. 2 (b) shows the squareness ratio (S), coercive force squareness ratio (S"), and the difference in relation to the La content; Fig. 2 (C) shows the residual magnetic flux. Density (Br product of Pg thickness (δ), Figure 2 (d
) is a relationship diagram of the product of saturation magnetic flux density (Bs) and film thickness (δ). However, at this time, all other conditions d are set to be the same, and in all cases, an RF sputtering device/cliff is used, and the output is sooo w and the total gas pressure is 4. Ox 10 Torr
, the substrate temperature is room temperature. Note that the Cr film thickness of the underlayer 3 was all 300 OA.

As can be seen from Fig. 2 (a) to (d), the magnetic properties that change the most with respect to La-containing tt are He (Fig. The range of
at 9f;

Regarding the La content in this range, Br・
δ.

Bs and δ in the figure (d) are both in the direction of decrease. However, this degree of decrease does not pose any particular problem in terms of magnetic properties.

Next, the change in HC of the magnetic layer 4 with respect to the thickness of the Cr film provided as the underlayer 3 is shown in the diagram of FIG. In this case, the magnetic layer 4 is made of Co-3 based on the results shown in FIG. 2(a).
0at' However, in FIG. 3, two other comparative examples are also shown to compare the present invention and the conventional example to clarify the effectiveness of the present invention.

The manufacturing method of the magnetic recording medium of Comparative Example 1 is exactly the same as that of the above-mentioned Examples, 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.
It is a thin film of 30at Ni and does not contain La.

Co-30at%Ni-5a, which explains the present invention from Fig. 3
The magnetic la of the koto La has a remarkable effect of increasing He due to the underlying Cr liquid film, and Cr ii lotus, IV 0, 3
It can be seen that Hc reaches saturation at a large value above μm. The result is clear. ``Furthermore, Bi can be used instead of Cr for the base layer 3, but if 1 g of Bj film is
By setting it to about A, the same effect as in the case of Cr can be obtained.

Furthermore, the corrosion resistance of the magnetic layer of the magnetic recording medium of the present invention will be mentioned.

Figure 4 shows Co-30at%Ni-5atcXLa exposed to an atmosphere at a temperature of 40°C and a relative humidity of 80%.
FIG. 5 is a diagram showing changes in the magnetic properties of a cQ magnetic recording medium, and FIG. In the case of FIG. 4 and FIG. 5, Comparative Example 1 and Comparative Example 2, which are the same as in FIG. 3, are also shown for comparison.

Figure 4 shows the changes in Br, δ and Hc of the magnetic layer with respect to the radiation f11 period of the magnetic recording medium.It is a circle.Although the initial values of the magnetic properties are different, the rate of change with the elapse of the standing time is about 1. It doesn't change. However, as shown in FIG. 5, the number of errors in the recording medium of the present invention is 12 w.
While the number of errors is only slightly counted after the eeks are left alone, the number of errors in Comparative Example 1 and Comparative Example 2 increases rapidly within a short period of time, making them unusable. This means that although the magnetic rotation of the entire magnetic layer does not show large changes over a relatively long period of time depending on environmental conditions, when exposed to an atmosphere such as humidity, conventional magnetic layers are This is due to subsequent corrosion and deterioration. On the other hand, it can be seen from FIG. 5 that the magnetic recording medium of the present invention having a magnetic layer to which a suitable amount of La is added also has excellent corrosion resistance. Although not shown in Fig. 5, 0.5
Similar results can be obtained when La is added in the range of ~12.5 at%.

Furthermore, as a result of conducting a C8S test using the magnetic recording medium of the present invention inserted into a magnetic recording device KMi, no scratches occurred on the surface of the recording medium even after 20,000 contact starts and stops, and the reproduction output was almost constant. It was found that it had sufficient durability without any deterioration.

As explained above, the magnetic recording medium of the present invention can be said to have both excellent magnetic properties and corrosion resistance.

〔Effect of the invention〕

In magnetic recording media such as magnetic disks, the thickness of the magnetic layer is increased to increase the recording density, and sputtered Co-Ni alloy thin films are used to improve magnetic properties. This magnetic layer has a drawback that the corrosion resistance in the usage environment is inferior to, for example, an iron oxide film in a Co-Ni alloy, whereas the present invention has a Co-Ni alloy with a magnetic layer of 0.5 to 12.5 at%. A magnetic recording medium is constructed in the same manner as before, using a magnetic layer containing h, and a non-magnetic base layer, an underlayer, a vi magnetic layer, and a protective lubricant film are deposited on a substrate. By adding La to the Co-Ni alloy of the magnetic layer, the Cr lower layer effectively works to increase He in the magnetic layer, while at the same time significantly improving the corrosion resistance of the magnetic layer itself. , the problems of magnetic properties and corrosion resistance, which have conventionally been contradictory, can be solved all at once, and both of these can be achieved in a single recording medium.Moreover, the recording medium of the present invention has good manufacturing efficiency and can achieve the output of a single recording medium. It has many great advantages in that it is durable and has a long service life.

[Brief explanation of drawings]

Figure 1 is a sectional view of the main part of the magnetic recording medium of the present invention;
The figure is a diagram showing the relationship between the La content and magnetic properties of the magnetic layer, Figure 3 is a diagram showing the change in Ha of the magnetic layer with respect to the thickness of the underlayer, and Figure 4 is a diagram showing the change in Ha of the magnetic layer with respect to the thickness of the underlayer. Figure 5 is a diagram showing changes in the magnetic properties of a magnetic recording medium exposed to an atmosphere of 80%. Figure 5 is a diagram showing changes in the number of errors.
The figure is a cross-sectional view of the main part of a conventional magnetic recording medium. DESCRIPTION OF SYMBOLS 1...Alloy substrate, 2...Nonmagnetic base layer, 3...Nonmagnetic metal base layer, 4.4&...Magnetic layer, 5...Protective lubricant film. ,・1.・6, :\ Figure 1 (a) (b) (c) (d) Figure 4 Figure 5 Figure 6

Claims (1)

[Scope of Claims] 1) A magnetic recording medium in which a nonmagnetic metal underlayer, a magnetic layer, and a protective lubricant film are successively laminated in this order on a nonmagnetic base coated with the main surface of a substrate. A magnetic recording medium characterized in that the magnetic layer is made of a Co-Ni alloy containing 0.5 to 12.5 at% of La. 2) A magnetic recording medium according to claim 1, wherein the magnetic layer has a La content of 2 to 11 at%. 3) A magnetic recording medium according to claim 1 or 2, characterized in that Cr is used as the non-magnetic metal sublayer. 4) A magnetic recording medium according to claim 1 or 2, characterized in that Bi is used as the nonmagnetic metal underlayer.