JPH0513332B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application] The present invention relates to a magnetic recording medium,
More specifically, the present invention relates to a metal thin film type magnetic recording medium whose main component is a ferromagnetic metal with excellent wear resistance. [Prior art] In recent years, the demand for high-density recording has become higher and higher.
It has been proposed to use a ferromagnetic metal layer as a magnetic recording layer, and furthermore, to use a cobalt alloy layer having perpendicular magnetic anisotropy as disclosed in Japanese Patent Publication No. 1983-91. However, in the case of a thin film type magnetic recording medium using such a metal thin film as a magnetic recording layer, there is a drawback that it is susceptible to wear and damage and lacks durability because of the large frictional resistance with the magnetic recording head. For this reason, various proposals have been made in the past in which a protective layer of organic polymer, high hardness metal, ceramics, etc. is further provided on a ferromagnetic metal thin film. However, the abrasion resistance of the thin film type magnetic recording medium, that is, the life span of the magnetic recording medium when the magnetic recording medium is repeatedly run on a magnetic recording head, is inferior to that of conventional coated magnetic recording media, and is not practical. However, the situation is still not satisfactory. [Object of the Invention] The present invention was made in view of the current situation, and is aimed at a thin-film magnetic recording medium having a recording layer made of a highly durable metal thin film mainly composed of a ferromagnetic metal. be. [Structure and operation of the invention] That is, the present invention provides a magnetic recording medium in which a recording layer made of a ferromagnetic metal thin film is formed on a substrate,
This magnetic recording medium is characterized in that a protective layer made of cobalt oxide containing Co ₃ O ₄ as a main component and having a columnar structure is provided on the recording layer. The present invention described above provides a protective layer of cobalt oxide, thereby making it possible to use a floppy disk for a magnetic head with a slider made of barium titanate, alumina ketane carbide (AlTiC), or the like.
It was discovered that it has a durability of more than 3 million cycles, which is the JIS standard. Therefore, the cobalt oxide of the present invention is Co ₃ O ₄
It is a cobalt oxide that has a columnar structure as its main component. Cobalt oxide with a columnar structure means that when a magnetic recording medium is cut into ultra-thin sections and observed with a transmission electron microscope, the side cross section of the cobalt oxide layer as shown in Figure 2. A pattern in which a vertical stripe pattern is observed in the direction perpendicular to the surface of the layer. In the figure, the lower layer is a magnetic layer, and the upper layer is a cobalt oxide layer, which is a protective layer. Moreover, it is analyzed by Auger electron spectroscopy (AES) that the main component is Co ₃ O ₄ . As is well known, the stoichiometry of a thin film may vary slightly, and when the cobalt oxide layer of the present invention is analyzed by the above-mentioned AES method, the stoichiometry is maintained in the film thickness direction even if the surface layer of several Å is excluded. A slight fluctuation was observed. Therefore, the protective layer was evaluated based on the AES analysis results at the center of the film thickness, specifically, from 50 to 200 Å from the surface, and was determined to have Co ₃ O ₄ as the main component as described above. Furthermore, this cobalt oxide was subjected to IRE analysis using the FT-IR-ATR method (ATR method using a Fourier transform infrared spectrometer (FT-IR) JIR-40X manufactured by JEOL Ltd.).
When surface analysis was performed using KRS-5 to remove the background of the substrate and magnetic layer by difference spectroscopy, it was found that 680 cm ^-1 in the range of 800 cm ^-1 to 400 cm ^-1
A spectral distribution was observed with the highest intensity absorption peak near 610 cm ^-1 and the second highest absorption peak near 610 cm -1 . The protective layer of cobalt oxide is formed by vacuum evaporation, sputtering, etc. in an oxidizing gas atmosphere using cobalt metal as an evaporation source and target, or by using a powder target of cobalt oxide such as _{Co3O4 .} Formed by RF sputtering. It is preferable to use a sputtering method. The present invention is applied to a known magnetic recording medium in which the recording layer is made of a ferromagnetic metal thin film. Specifically, a ferromagnetic metal thin film layer for in-plane recording made of metals such as iron, cobalt, nickel, or alloys thereof is provided on a substrate, a cobalt-based alloy thin film having perpendicular magnetic anisotropy, etc. with a ferromagnetic metal thin film layer for perpendicular recording, or iron, permalloy,
Known thin-film magnetic recording for in-plane or perpendicular recording, such as a metal layer with high magnetic permeability such as a cobalt-niobium-zircon alloy, followed by the above-mentioned metal thin film layer for perpendicular recording. There is a medium. Among these, it is more preferably applied to perpendicular magnetic recording media than the alloy thin film mainly composed of cobalt-chromium shown in the embodiment. The substrate may be a polymer film such as polyester or polyimide, a glass plate,
Aluminum alloy plates, etc. are used, and magnetic tape,
Floppy disks, magnetic disks, etc. are selected depending on the application. The present invention has the above-mentioned columnar visible structure.
By providing a protective layer made of cobalt oxide containing Co ₃ O ₄ as a main component on the recording layer, it was possible to greatly improve the durability of the recording layer. Examples of the present invention are shown below. [Embodiment] FIG. 1 shows an example of the structure of the present invention, which is a flexible double-sided perpendicular magnetic recording medium for a floppy disk. A polyethylene terephthalate film with a thickness of 50 μm is used as the base 1, and a 0.4 μm film is applied on both sides.
A thin metal layer 2 with high magnetic permeability made of a nickel-iron alloy of 0.4 μm and cobalt chromium (chromium) of 0.4 μm.
20Wt%) perpendicular magnetic recording layer 3 made of an alloy thin film
Using the opposed target sputtering device disclosed in JP-A-59-193526, these were sequentially laminated in the same manner as in Example 1, and then reactivity was applied in an oxidizing gas atmosphere using cobalt metal as a target. A protective layer 4 having a thickness of 320 Å was laminated by a sputtering method to produce a magnetic recording medium of the example. A transmission electron micrograph of the formed protective layer 4 is shown in FIG. The figure was taken at a magnification of 100,000 times, and in the figure, the upper layer is the protective layer 4 and the lower layer is the perpendicular magnetic recording layer 3. It can be seen from the figure that the protective layer 4 of this example exhibits a columnar pattern in a direction perpendicular to the layer surface, and has the visible columnar structure of the present invention.
In addition, as mentioned above, the fact that the protective layer 4 of this example is made of cobalt oxide whose main component is Co ₃ O ₄ can be confirmed by the AES method,
Confirmed by FT-IR-ATR method. A disk with a diameter of 5.25 inches was punched out from the magnetic recording medium of the example obtained as described above, and evaluated using an evaluation device using a commercially available floppy disk drive device. The results are shown in the table. The table shows glass (BK7) (Example 1), barium titanate (Example 2), and alumina titanium carbide (AlTiC) for the sliding part (head slider part).
The surface roughness of the sample was evaluated as follows after being rotated for 3 million passes at 300 rpm using an evaluation device using a dummy head (Example 3). In other words, for durability evaluation, the surface roughness of the sample before and after the sliding test was determined as the center line average roughness CLA using a surface roughness meter (SURFCOM, manufactured by Tokyo Seimitsu Co., Ltd.), and the CLA value after the sliding test was calculated. This was done by calculating the relative surface roughness divided by the CLA value before sliding. For comparison, the results of evaluation of perpendicular magnetic recording media having the same structure as in the above-mentioned example except that no protective layer was provided are shown as Comparative Examples 1, 2, and 3.

[Table] As is clear from the table, in the examples using the protective layer made of cobalt oxide of the present invention, there was little change in the surface roughness of the media before and after the sliding test, which was better than any of the comparative examples. The results showed high durability. Furthermore, it has become clear that alumina titanium carbide (AlTiC) is the best material for the head slider material to be combined with this protective layer. The present invention described above is not limited to the floppy disks and perpendicular magnetic recording media shown in the examples, but can be applied to so-called hard disks such as alumina disks subjected to alumina oxidation treatment, and magnetic tapes. Needless to say, it is possible. Further, as for the manufacturing method of the recording layer and the protective layer, other known film forming means other than those in the examples can be applied.

[Brief explanation of the drawing]

FIG. 1 is a partial side cross-sectional view showing the structure of an embodiment of the present invention, and FIG. 2 is an electron micrograph (100,000x magnification) of a cobalt oxide having a columnar structure according to an embodiment of the present invention. . 1: Substrate, 2: High magnetic permeability metal thin film layer, 3: Cobalt-chromium alloy thin film layer, 4: Cobalt oxide protective layer.

Claims (1)

[Scope of Claims] 1. In a magnetic recording medium in which a recording layer made of a ferromagnetic metal thin film is formed on a substrate, a cobalt oxide mainly composed of Co ₃ O ₄ having a columnar-looking structure on the recording layer is used. A magnetic recording medium characterized by being provided with a protective layer. 2. The magnetic recording medium according to claim 1, wherein the recording layer is a perpendicular magnetic recording layer. 3. Claim 2, wherein the perpendicular magnetic recording layer is made of an alloy thin film containing cobalt-chromium as a main component.
Magnetic recording medium described in Section 1.