JPH0580805B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a magnetic storage body used in magnetic storage devices (magnetic disk devices, magnetic drum devices, etc.). Most of the magnetic storage bodies currently in practical use have discontinuous media. This discontinuous magnetic storage medium is made of r-Fe ₂ O ₃ , CrO ₂ , Fe, Fe-Co
Magnetic storage media are manufactured by mixing and dispersing magnetic particles such as in a binder made of organic resin, coating it on a substrate, drying it, and baking it, so magnetic storage media are discontinuous at the level of the size of the magnetic particles. . However, in recent years, due to the demand for higher recording densities in magnetic storage media, research and development of magnetic storage media consisting of continuous thin film media has been actively conducted. This continuous thin film medium mainly consists of metal thin films made by methods such as plating, vacuum evaporation, sputtering, and ion blating, and Fe ₃ O ₄ or R films made by methods such as vacuum evaporation, sputtering, and ion blating. -Those made of metal oxide thin films such as Fe ₂ O ₃ are known. Magnetic recording media made of metal thin films (hereinafter referred to as metal thin film media) are prone to corrosion in poor atmospheres such as high temperature and high humidity, and metal thin film media with sufficient corrosion resistance are not yet known. SUMMARY OF THE INVENTION In view of the above-mentioned current situation, an object of the present invention is to provide a magnetic memory having a metal thin film medium having excellent magnetic properties and extremely excellent corrosion resistance. That is, in the magnetic storage body of the present invention, a metal disk is coated with a non-magnetic metal layer or a non-magnetic metal oxide layer, and a layer is coated on the non-magnetic metal or non-magnetic metal oxide layer.
An alloy consisting of ~25 atomic percent vanadium, 20-32 atomic percent platinum, and the balance cobalt,
or 1 to 15 atomic percent tungsten and 20
A thin metal film medium of an alloy consisting of ~32 atomic percent platinum and the balance cobalt is coated, and a protective film is coated on the medium. Next, the present invention will be explained in detail with reference to the drawings.
FIG. 1 is a partial cross-sectional view of the magnetic storage body of the present invention. In FIG. 1, aluminum alloy is most often used as the metal disk 1 of the magnetic storage body because it is light, has good workability, and is inexpensive, but titanium alloy may be used in some cases. The surface of the base is machined to create small waviness (less than 50μm in the circumferential direction,
100μm or less in the radial direction). Next, a non-magnetic metal layer 2 of nickel-phosphorus alloy or aluminum oxide is coated on this base 1 by plating, and the surface of this base body 2 is mechanically polished to a mirror finish with a maximum surface roughness of 0.03 μm or less. . Next, a metal thin film medium made of vanadium or cobalt containing tungsten and platinum is coated as a metal magnetic medium 3 on the mirror-polished surface of the base body 2 by high-frequency sputtering. Next, a protective film 4 typified by S _i O ₂ is placed on the metal thin film medium 3.
is coated by high frequency sputtering method. Metal thin film media has a coercive force (He) of 500 to 1200 Oe (Oersted), a saturation magnetic flux density (Bs) of 10000 G (Gauss) or less, a squareness ratio (Br/Bs) of 0.7 to 0.9, a coercive force squareness ratio (S ^* ) of 0.7 to 0.9. It exhibits excellent hysteresis characteristics as a magnetic recording medium. Here, the squareness ratio S is a value obtained by dividing the residual magnetic flux density B _r by the saturation magnetic flux density Bs. The above properties are highly dependent on the amount of vanadium or tungsten in the metal thin film medium. Figure 2,
Figure 3 shows the changes in residual magnetic flux density Br, coercive force Hc, and squareness ratio depending on the atomic percentage of vanadium or tungsten in the metal thin film medium.
In the range of 1 to 15 atomic %, a coercive force of 500 Oe or more and a squareness ratio of 0.9 to 0.7 can be obtained as shown in FIGS. 2 and 3. FIG. 4 shows the rate of change in saturation magnetic flux density (ratio to the initial saturation magnetic flux density) due to corrosion when immersed in water. Storage media containing 20 atomic % or more of Pt (examples of the present invention) can be used as magnetic storage media without any change, but those containing 9 atomic % of Pt (Comparative Example 2) or those containing no Pt (Comparative Example 1) However, corrosion rapidly increases and it cannot be used as a magnetic storage medium. In addition, the coercive force and saturation magnetic flux density do not change significantly when the Pt content is less than 32 atomic %, but when it exceeds 37 atomic %, the magnetic properties deteriorate and it is difficult to use it as a magnetic storage medium. Therefore, the optimum range for Pt is 20 to 32 atom %. As described above, the cobalt alloy film containing vanadium or tungsten and platinum in the composition ratio of the present invention is excellent as a magnetic storage medium. The protective film coated on the metal thin film medium 3 is preferably hard, and is made of metals such as osmium, ruthenium, iridium, manganese, tungsten, or oxides, nitrides, or carbides of silicon, titanium, tantalum, or hafnium, or boron. , carbon or an alloy of boron and carbon, or polysilicic acid. Polysilicic acid is an oxide of silicon, and it can be converted into tetrahydroxysilane (Si
It is formed by thermal decomposition of (OH) ₄ ) at 200-300℃. Si(OH) ₄ →SiO ₂ +2H ₂ O Further, on top of the protective film 4, R-G (R is C number 10 to 40)
The saturated or unsaturated hydrocarbons or fluorinated hydrocarbons G are COOH, OH, NH ₂ , COOR ¹ , Si(oR ¹ ) ₃ ,
It is also possible to apply a lubricant consisting of a functional group such as CONH ₂ or a lubricant such as fluorinated alkyl polyether or polytetrafluoroethylene telomer. Next, the present invention will be explained by giving some examples. Example 1 Specific magnetic alloy 2 is placed on a disc-shaped aluminum alloy disc 1 which has been finished with sufficiently small waviness (50 μm or less in the circumferential direction and 10 μm or less in the radial direction) by lathe processing and thermal straightening. A nickel-phosphorus alloy was plated to a thickness of approximately 50 μm, and the nickel-phosphorus plated film was mirror-polished to a maximum surface roughness of 0.02 μm and a thickness of 30 μm. Next, on this nickel-phosphorus plating film, argon pressure was applied as a metal magnetic medium 3 using a high frequency sputtering method.
A cobalt alloy thin film containing 9 atomic percent vanadium and 20 atomic percent platinum was coated with a film thickness of 500 A at 4X10 ^-2 torr and a power density of 1 W/cm ² . Further, this metal magnetic medium 3 was coated with SiO ₂ to a thickness of 200 Å by high frequency sputtering to produce a magnetic disk. Coercive force Hc, residual magnetic flux density Br, squareness ratio S, and coercive force squareness ratio S ^* are 960oe, 6500G, respectively.
It was 0.85, 0.85. Example 2 A magnetic disk was fabricated in the same manner as in Example 1 except that the metal magnetic medium 3 was coated with a cobalt alloy thin film containing 6 atomic percent of tungsten and 32 atomic percent of platinum to a thickness of 800 Å. Hc, Br, S
and S ^* were 950oe, 4500G, 0.8, and 0.8, respectively. Example 3 A magnetic disk was fabricated in the same manner as in Example 1 except that the metal magnetic medium 3 was coated with a cobalt alloy thin film containing 3 atomic percent of tungsten and 32 atomic percent of platinum to a thickness of 500 Å. Hc, Br, S, S ^* are respectively 1200oe, 5900G,
It was 0.85, 0.85. Example 4 A magnetic disk was fabricated in the same manner as in Example 1, except that the metal magnetic medium 3 was coated with a cobalt alloy thin film containing 2 atomic percent vanadium and 20 atomic percent platinum to a thickness of 300 Å. Hc, Br, S, S ^*
were 1100oe, 9600G, 0.85, and 0.85, respectively. Example 5 A magnetic disk was fabricated in the same manner as in Example 1 except that the metal magnetic medium 3 was coated with a cobalt alloy thin film containing 10 atomic percent of tungsten and 32 atomic percent of platinum to a thickness of 1500 Å. Hc,Br,S,
S ^* were 600oe, 3200G, 0.80, and 0.80, respectively. Example 6 A magnetic disk was fabricated in the same manner as in Example 1 except that the metal magnetic medium 3 was coated with a cobalt alloy thin film containing 13 atomic percent vanadium and 20 atomic percent platinum to a thickness of 800 Å. Hc, Br, S, S ^*
were 900oe, 5000G, 0.85, and 0.85, respectively. Example 7 A magnetic disk was fabricated in the same manner as in Example 1, except that the metal magnetic medium 3 was coated with a cobalt alloy thin film containing 10 atomic percent of tungsten and 20 atomic percent of platinum to a thickness of 2000 Å. Hc,Br,S,
S ^* were 800oe, 3200G, 0.80, and 0.80, respectively. Example 8 A magnetic disk was fabricated in the same manner as in Example 1, except that the metal magnetic medium 3 was coated with a cobalt alloy thin film containing 25 atomic percent vanadium and 20 atomic percent platinum to a thickness of 500 Å. Hc, Br, S, S ^*
were 700oe, 2000G, 0.80, and 0.80, respectively. Example 9 A magnetic disk was fabricated in the same manner as in Example 1, except that the metal magnetic medium 3 was coated with a cobalt alloy thin film containing 15 atomic percent of tungsten and 20 atomic percent of platinum to a thickness of 500 Å. Hc,Br,S,
S ^* were 550oe, 2000G, 0.80, and 0.80, respectively. Example 10 Same as Example 1, but with argon pressure 4×
A magnetic disk was made at 10 ^-2 _tprr and a power density of 15W/cm ² . Example 11 Same as Example 1, but with argon pressure
A magnetic disk was made with 8X10 ^-3 _tprr and a power density of 15W/cm ² . Example 12 Same as Example 2, but with argon pressure
A magnetic disk was made with 4X10 ^-2 _tprr and a power density of 15W/cm ² . Example 13 Same as Example 2, but with argon pressure
A magnetic disk was made with 8X10 ^-3 _tprr and a power density of 15W/cm ² . Example 14 Same as Example 1 or 2, except that the surface of the aluminum alloy disk 1 was coated with aluminum oxide as a non-magnetic metal oxide layer by anodizing as a non-magnetic alloy layer, and the aluminum oxide was coated with a maximum surface roughness of 0.02 μm. I polished it to a mirror finish and made a magnetic disk. Example 15 Magnetic disks were prepared in the same manner as in Example 1 or 2 except that the following materials were coated as protective films to a thickness of 800 Å by sputtering.

[Table] When polysilicic acid is used for the protective film, it is necessary to form up to the metal magnetic medium in the same way as in the previous example, apply a solution of tetrahydroxysilane in isopropyl alcohol thereon, and bake it at 300°C for 1 hour. A protective film of polysilicate with a thickness of 800 Å was formed using the following steps. Comparative Example 1 A magnetic disk was fabricated in the same manner as in Example 1, except that a nickel-phosphorus plated film was coated with cobalt as a metal magnetic medium 3 to a thickness of 500 Å via a 1 μm thick chromium film. Coercive force Hc, residual magnetic flux density Br,
Squareness ratio S and coercive force squareness ratio S ^* are each 600Oe,
It was 13600G, 0.8, 0.8. Comparative Example 2 A magnetic disk was fabricated in the same manner as in Example 1 by coating a cobalt alloy thin film of 9 at% platinum and the balance cobalt to a thickness of 500 Å. The coercive force Hc, residual magnetic flux density Br, squareness ratio S, and coercive force squareness ratio S ^* were 800 Oe, 11000 G, 0.80, and 0.80, respectively. Using the magnetic disks shown in Examples 1 to 15 and Comparative Examples 1 and 2 above, electromagnetic conversion characteristics, head wear tests, environmental tests, and water immersion corrosion tests were conducted, and the following characteristics were obtained. Regarding the electromagnetic conversion characteristics, regarding the disks of Examples 1 to 15
A recording density of 40,000 to 80,000 FRPI was obtained, but a recording density of only 20,000 FRPI was obtained in the disks of Comparative Examples 1 and 2. As for the abrasion test with the head, no scratches were observed on the disk surface after 20,000 contact start-stop tests.
In addition, when we conducted an environmental test in which the disk was left at a temperature of 80°C and a relative humidity of 90% for 6 months, the increase in the number of errors for Examples 1 to 15 and Comparative Example 2 was 0, but for the disk of Comparative Example 1. The error increased by a factor of 100. Finally, cut the disks of Examples 1 to 15 and Comparative Examples 1 and 2 to make sections of 15 mm x 15 mm.
When we investigated the change in saturation magnetic flux density Bs by immersing it in water at 25℃ for several months, we obtained the results shown in Figure 4. Figure 4 shows the rate of change in saturation magnetic flux density Bs (Bs/Bo, Bo
represents the change in the saturation magnetic flux density (before immersion) over time; the closer the value is to 1.0, the better the corrosion resistance. In other words, in Examples 1 to 15, there was no change in Bs at all after being immersed in water for one month, but in Comparative Example 1, it was 50%, and in Comparative Example 2.
Bs decreased by 25%. From the above results, it was found that the magnetic memory of the present invention has excellent corrosion resistance (environmental resistance), wear resistance, and high recording density characteristics.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional view of an embodiment of the magnetic storage body of the present invention. In the figure, 1 is a substrate, 2 is a non-magnetic alloy layer, 3
4 is a metal thin film medium, and 4 is a protective film. Figure 2 is a characteristic diagram showing the changes in residual magnetic flux density, coercive force, and squareness ratio of the metal thin film medium used in this magnetic storage body depending on the atomic percentage of vanadium in the metal thin film medium, and Figure 3 is a characteristic diagram showing the changes in the residual magnetic flux density, coercive force, and squareness ratio depending on the atomic percentage of vanadium in the metal thin film medium. FIG. 2 is a characteristic diagram showing changes in residual magnetic flux density, coercive force, and squareness ratio in a metal thin film medium used in a storage body depending on the atomic percent of tungsten in the metal thin film medium. FIG. 4 is a characteristic diagram showing the rate of change in saturation magnetic flux density of the metal thin film medium used in the present magnetic storage body depending on the water immersion time.

Claims (1)

[Claims] 1. A non-magnetic metal layer or a non-magnetic metal oxide layer is coated on a metal disk, and 1 to 25 atomic percent vanadium and 20 to 32 atoms are coated on the non-magnetic metal or non-magnetic metal oxide layer. An alloy thin film medium of an alloy consisting of 1% platinum and the balance cobalt, or an alloy consisting of 1 to 15 atomic percent tungsten and 20 to 32 atomic percent platinum, the balance cobalt is coated, and a protective film is coated on the alloy thin film medium. What is claimed is: 1. A magnetic storage body characterized by being constructed by being coated with. 2. The magnetic memory according to claim 1, wherein the nonmagnetic metal layer is nickel monophosphorus. 3. The magnetic memory according to claim 1, wherein the nonmagnetic oxide layer is aluminum oxide. 4. The magnetic storage body according to claim 1, wherein the protective film is made of osmium, ruthenium, iridium, manganese, or tungsten. 5. The magnetic memory according to claim 1, wherein the protective film is an oxide, nitride, or carbide of silicon, titanium, tantalum, or hafnium. 6. The magnetic memory according to claim 1, wherein the protective film is made of boron, carbon, or an alloy of boron and carbon. 7 Claim 1 in which the protective film is polysilicic acid
Magnetic storage medium described in Section 1.