JPS6243832A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance of a magnetic layer by forming the magnetic layer of a Co alloy contg. Ni, Cr and Mo. CONSTITUTION:A substrate surface layer 2 is coated on a nonmagnetic substrate 1 and further the magnetic layer 4 is coated via a nonmagnetic metallic underlying layer 3 on the substrate surface layer. A thin cobalt-nickel alloy magnetic film 4 contg. chromium and molybdenum is sued as the magnetic layer. A protective lubricating layer 5 is further coated on the thin magnetic film. The magnetic layer formed by continuous sputtering via the underlying layer has itself the excellent magnetic characteristics and corrosion resistance and therefore the magnetic recording medium having the durability and excellent magnetic characteristics is obtd.

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, which has a magnetic layer made of a Co alloy on a nonmagnetic substrate and is used in a magnetic recording device or the like.

[Prior art and its problems]

With the increase in the recording density of magnetic recording media used in magnetic disk devices, etc., the magnetic layer of magnetic recording media has been thinned from about 1-tna to 0.1 tna or less, and the coercive force (llc) has also increased. Need to improve. At the same time, sputtering and plating methods, which can easily form thin films, are attracting attention in place of spin-coding methods for forming magnetic layers, and Co-based alloys are being used instead of conventional iron oxides as materials for magnetic thin films. . However, as alloy magnetic thin films have been researched, although they have excellent magnetic properties, corrosion resistance has become a problem. Currently, it is not put into practical use because its magnetic properties deteriorate. In terms of corrosion resistance, iron oxide magnetic thin films formed by sputtering are excellent, but their magnetic properties, especially the low residual magnetic flux density Br, and the complexity of this manufacturing method, especially the sputtering conditions and heat treatment, etc. It has drawbacks such as problems. Therefore, it is desired to compensate for the lack of corrosion resistance of the Co alloy magnetic layer. For this purpose, a method is used in which a protective film is formed on the surface □ to protect the magnetic layer. However, it is also necessary to consider the lubricity with the magnetic head and the hardness and density of the thin film for protection, and a protective film that satisfies both of these requirements has not yet been found. Therefore, chromium is added to Co alloy to improve corrosion resistance.
When used in combination with a protective film, magnetic recording media with excellent magnetic properties and Ni7 erodibility are being developed. - Generally, adding Cr to improve corrosion resistance is often done in the field of metals, but Cr alone improves corrosion resistance by 1 to 1, but causes deterioration of magnetic properties. Easy to invite.

[[Target] of the invention]

An object of the present invention is to improve the corrosion resistance of a Co alloy magnetic layer without lowering its magnetism, thereby providing a recording medium that is used in combination with a protective film and has excellent corrosion resistance and magnetic properties. .

[Summary of the Invention] According to the present invention, the magnetic layer contains NI+Cr, Mo. By forming the magnetic layer from an alloy, the corrosion resistance of the magnetic layer is improved and the object described in item L is achieved. It is desirable that such a magnetic layer be formed by a sputtering method continuously performed on a non-magnetic underlayer formed by a sputtering method on the magnetic substrate-I. DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a partial cross-sectional view of a magnetic recording medium according to the present invention. The magnetic recording medium according to the present invention has two
1 Body surface layer 2 is coated with IW tongue 1,) 1 (Body surface layer 1- is further coated with layer 4 through Jl[f-th 4 metal dome layer 3, 71 layer and L-C41 layer 1 light, and contains molybdenum = 1 pal 1;
A thin film 4 made of Noryl resin is used. More m!
'P+'! v1191 is coated with an EW retaining lubricant layer 5. ■ Non-Cfl property of recording medium), (+I
Aluminum, mini-J, and platinum substrates are often used as I, 1, but it is also possible to use S plates in some cases. This board is placed on a predetermined surface I.
11 After increasing parallelism and flatness, the substrate surface layer?
Cover. What is this layer? -No'y-Ruphorous alloy plating or alumite coating is desirable, and a certain level of hardness is required, and in Table 1fi, a mirror finish is achieved by mechanical polishing. Next, No. 1 (L of the body surface IM2 is a non-primitive metal represented by chromium. This underlayer 3 is used to protect the metal magnetic thin film 4 (,! Taka (II).
It has the effect of increasing O, and the thickness of this base layer 3 has a k
Even if = +, the coercive force of the magnetic layer 4 is saturated (in one direction,
The saturated thickness varies greatly depending on the material and other factors. For example, in the case of Cr, there are about 7,000 people, but in the case of Bl, there are 500 people.
It is about the size of a person. Next, a magnetic layer 4 made of Co containing Ni+Cr and Mo is formed on one part of the underlayer 3 by sputtering. Finally, carbon, 5
IOI, 513N4. Protective lubricant film such as SiC5
is coated by sputtering method. The magnetic properties of the Co-N1-Cr-Mo magnetic layer are determined by the coercive force (
llc) 300-10000s, residual magnetic flux density (Br)
450 (1~9500Gs. Coercive force squareness ratio (S") is in the range of 0.7~0.9, C
It varies greatly depending on the amount of r and Mo. A Co-Ni alloy magnetic thin film shows the maximum coercive force near about 30 atomic% Ni, and when Cr is added to a Co-30 atomic% Ni alloy magnetic thin film, it shows the largest coercive force near about 8 atomic% Cr. . Furthermore, by adding Mo to this alloy thin film, it shows the maximum coercive force around 4 atomic % Mo, and from this result, it can be used as a magnetic recording medium that can perform high-density recording in the range of 2 to 8 atomic % Mo. known to be usable. Examples and comparative examples will be given below, and their test results will be described. Example 1: As a non-magnetic substrate 1, a substrate surface was formed on a disk-shaped aluminum disk whose surface had sufficiently small waviness, that is, 20 nm or less in both the circumferential and radial directions, by lathe processing and pressure annealing. As layer 2, an N1-P alloy was formed to a thickness of about 30p by electroless plating, and then a N1-P plating film was formed with an average surface roughness of 0.02 square meters. A nonmagnetic substrate was prepared by mirror polishing to a thickness of 15 mm. After forming the underlayer 3 on this non-magnetic substrate,
Finally, a magnetic disk medium was fabricated by coating C as a surface protective lubricant layer to a thickness of 500 mm by sputtering. Coercive force Hc of magnetic properties. Residual magnetic flux density Br is 7000e and 9500G, respectively.
It was s. Example 2: After producing a non-magnetic substrate in the same manner as in Example 1, 500 pieces of Bi were added as an underlayer on the non-magnetic substrate, followed by Co-30%Ni-8%Cr-4 as a magnetic layer. %Mo-alloy to a thickness of 600mm, and finally S as a surface protective lubricating layer.
A magnetic disk medium was fabricated by continuously forming IO□ to a thickness of 500 mm using a sputtering method.
c and Br were 7000e and 9500Gs, respectively. Comparative Example 1: A magnetic disk medium was fabricated in the same manner as in Example 1, except that the thickness of the Cr layer 3 was 5000 mm, and the magnetic layer 4 was made of only Co, using a continuous sputtering method. llc
, Br were 6000e and 1100OGs, respectively. Comparative Example 2: Same as Example 1, except that the thickness of the Cr layer 3 was 2000 mm, and the magnetic M4 was a Co-30% N1 alloy by continuous sputtering method (an n-type disk medium was fabricated). lc and Br are 6500e and l100 respectively
They were OGs. Comparative Example 3: Same as Example 1, but the thickness of the Cr layer 3 was set to 1000, and the magnetic layer 4 was made of Co-30%N+-8%Cr.
A magnetic disk medium was fabricated using an alloy using a continuous sputtering method. Ilc and Br are each 7000e. It was 9500Gs. Comparative Example 4: Same as Example 1, but after forming Cr as the base N3, air was once introduced into the sputtering tank, the vacuum was drawn again, and the sputtering gas pressure was set to a predetermined level, and then the magnetic layer 4 was formed. A Go-30%N+-8%Cr4%Mo alloy was sputtered onto the base N3. Thereafter, air was again introduced into the sputtering tank and the tank was further evacuated to a predetermined sputtering gas pressure, and then a C film was sputtered as a protective lubricant layer 5 on the magnetic layer 4 to produce a magnetic disk medium. The thickness of each layer was the same as in Example 1. Hc and Br were 2000e and 8000Gs, respectively. As shown in Example 1 and Comparative Example 4, by exposing the underlayer to the atmosphere after sputtering the underlayer 3 and before sputtering the magnetic layer 4, the effect of the underlayer is weakened and the coercive force is 700 (l).
e to 200[1e. This is the same as when the base layer 3 is sputtered and then left in a sputtering bath for a long time without being exposed to the atmosphere. Figure 2 shows the change in coercive force when the thickness of the underlayer in Example 1 and Comparative Examples 1 to 3 is changed. is higher than that of the comparative example, which indicates that stable magnetic properties can be obtained by reducing the thickness of the underlayer and shortening the formation time to produce a magnetic recording medium. The magnetic recording media obtained in Examples and Comparative Examples were
When installed in an actual magnetic disk drive and subjected to a C8S test and an environmental test, the media of the example showed no scratches on the disk surface, and showed sufficient durability with little reduction in playback output. Understood. However, in the medium of Comparative Example 4, scratches occurred on the surface. In the environmental test, the magnetic disk medium was immersed in water at 25°C to observe the change in the number of errors.As shown in Figure 3, the medium of the embodiment of the present invention had sufficient corrosion resistance, judging from the number of errors that occurred. I found out something. Effects of the Invention The present invention provides a C
o-N1 alloy continuous thin film (N layer and a protective lubricant layer on top of it; in particular, the magnetic layer itself, which is formed by continuous sputtering through the underlayer, has excellent magnetic properties and corrosion resistance. Therefore, a magnetic recording medium that is durable and has excellent magnetic properties can be obtained.Furthermore, since the thickness of the underlayer can be kept thinner than before, it becomes possible to manufacture a magnetic recording medium at a lower cost.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional view of an example of the present invention, FIG. 2 is a diagram showing changes in coercive force depending on the thickness of the underlying layer of the magnetic r# film of the example of the present invention and a comparative example, and FIG. 3 1 is a diagram showing changes in the number of errors in environmental tests of Examples and Comparative Examples of the present invention. 1: Nonmagnetic substrate, 2: Substrate surface layer, 3: Nonmagnetic metal underlayer, 4: Co-N1-Cr-Mo alloy (supporting layer,
5: Protective lubricant layer. Quality Patent Attorney Kyo Yamaguchi

Claims (1)

[Scope of Claims] 1) A magnetic recording medium having a Co alloy magnetic layer covered with a protective film, characterized in that the magnetic layer is made of a Co alloy containing Ni, Cr, and Mo. 2) The medium according to claim 1, characterized in that the magnetic layer is formed by sputtering continuously on a non-magnetic underlayer formed by sputtering on a non-magnetic substrate. magnetic recording media.