JPS58200513A - Magnetic memory medium - Google Patents

Abstract

PURPOSE:To obtain a metal thin film medium having a high residual magnetic flux density and excellent corrosion proof characteristic by forming a metal thin film medium with cobalt alloy containing platinum of a particular atom percent. CONSTITUTION:A metal thin film medium shows an excellent hysteresis characteristic as a magnetic recording medium with degaussing force (Hc) of 300-2,000 Oe, saturated magnetic flux density (Bs) of 8,500-1,400 G, squareness ratio (Br/ Bs) of 0.7-0.9, squareness of coersive force (S*) of 0.7-0.9. This characteristic depends largely on amount of platinum in cobalt and film thickness. When change of anti-magnetic force due to atom percent of platinum is considered, it can be used as a magnetic recording medium which assures high recording density can be used within the 7-40 atom percent of platinum.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic storage medium, and more particularly to a magnetic alloy comprising a thin metal film.

The mainstream of magnetic storage media currently in practical use is discontinuous media. This discontinuous medium magnetic storage medium is a-
Fe, 03. Magnetic storage media are manufactured by mixing and dispersing magnetic particles such as Cry, Fe, and Fe-Co in a binder made of organic resin, coating the mixture on a substrate, drying it, and baking it. It is discontinuous in the level of strength.

However, in recent years, the key to increasing the recording density of magnetic storage media is
Recently, research and development of magnetic storage media made of continuous thin film media has been actively conducted. This continuous thin film medium is mainly composed of gold film made by methods such as plating, vacuum evaporation, sputtering, and ion blating, and Fe, O. Alternatively, those made of metal oxide thin films such as α-Fe, O, etc. are known. The metal oxide thin film has a small residual magnetic flux density, so it is difficult to obtain a large playback output and is limited in terms of high recording density. On the other hand, magnetic storage media made of metal thin films (hereinafter referred to as metal thin film media) have a large t-X residual magnetic flux density and are promising, but they tend to corrode in poor atmospheres such as high temperature and high humidity, and metals with sufficient corrosion resistance are Thin film media are not yet known.

In view of the above-mentioned current situation, an object of the present invention is to provide a metal thin film medium having a large residual magnetic flux density and extremely excellent corrosion resistance.

That is, the metal thin film medium of the present invention is comprised of a cobalt alloy containing 7 to 40 atomic percent platinum.

The metal thin film medium of the present invention has a coercive force (He) of 300 to 200.
0 ce (engineered), saturation magnetic flux density (Bs)
8.500-14,000 G (Gauss), squareness ratio (
Br/Bs)0.7-0.9. Coercive force squareness ratio (S”) 0
．． It exhibits excellent steresis properties as a magnetic recording medium in the range of 7 to 0.9.

The above characteristics largely depend on the amount of platinum in cobalt and the film thickness.

FIG. 1 shows the change in coercive force depending on the atomic percent of platinum in cobalt, so it can be used as a magnetic storage medium capable of high recording density in the range of 7 to 40 atomic percent of platinum.

FIG. 2 shows the change in saturation magnetic flux density depending on the atomic percent of platinum in cobalt, and a large value of 9,800 to 14,000 G (Gauss) is obtained in the range of 7 to 40 atomic percent of platinum.

FIG. 3 shows the change in coercive force depending on the film thickness, and the thinner the film thickness, the higher Hc becomes, and characteristics suitable for a higher density fK can be obtained.

As described above, it has been found that the metal thin film of the present invention made of a cobalt alloy containing 7 to 40 atomic percent of platinum is excellent as a magnetic recording medium.

Platinum-cobalt magnets, which are generally used as permanent magnets, have a composition of 42 to 73 atomic percent platinum in cobalt (generally 50 atomic percent), so they are excellent metal thin film media in the range of 7 to 40 atomic percent platinum. It is a shame that this is achieved.

Next, the present invention will be explained by giving some examples.

Example 1 5m x 4s on a Co target with a diameter of 100u and a thickness of 1cm
m thickness 0.1 wx-f) Pt piece with area ratio Co/P
It is arranged so that i=4.5 and is installed in a sputtering apparatus. Next, after setting up the CD substrate at a distance of 4.5 mm from the target, sputtering was performed in an argon atmosphere of 2 x 10-torr at an anode voltage of 2.2 KV% and a town voltage of 300 W for 10 seconds, 1 minute, 3 minutes, and 6 minutes, respectively. A sample was prepared by depositing a cobalt alloy thin film containing 20 atomic percent platinum on a vtJ substrate by sputtering at room temperature for 10 minutes. The film thickness of each sample is sou, 'aooλ, tao
The oA, tsoou, and aooo are large, and the hysteresis characteristics are coercivity of 2000ae, 1700ae, and 11, respectively.
The sizes are 10oe, 850ae, and 700ae, the squareness ratio (Br/Bs) is 0.9 to 0.7, and the saturation magnetic flux density f is 11400 Gauss.

Example 2 Same as Example 1 except that the area ratio of Co and Pt is Co/P.
With i = 2.68, cobalt alloy thin films containing platinum for 30s are 50^, 300A, 90GA, 1800A, 30
Make a sample by depositing each with a film thickness of 00A.9.

The hysteresis characteristic of each sample is a coercivity of 1400G! .

1100ae, 700ce, 550@, 550o
e and the squareness ratio (Br/Bs) is 110.9 to 0
．． 7 The saturation magnetic flux density f was 9900 Gauss. Example 3 The same pressure as in Example 1 was applied, except that the area ratio of Co and Pi was αzoPI
-1,72 is a cobalt alloy thin film containing 40 pieces of platinum, 50^, 300 large, 900λ, 1soof, 3o
Samples were prepared by depositing each film with a film thickness of ooA.

The hysteresis characteristic of each sample has a coercivity of 550Q! .

45G@, 450oe, 340ae, 300oe, 28
0oe, and the squareness ratio (Br/Bs) is 0.8 to 0.
．． 6 The saturation magnetic flux density is $500 Gauas.

Example 4 Same as Example 1 except that the area ratio of CO and Pt is Co/P.
i-IQ, 33, a cobalt alloy thin film containing 10- platinum is sou, 300μ, 900^, 1800λ, 30
Samples were prepared by depositing each film with a film thickness of 00A.

The hysteresis characteristic of each sample has a coercivity of 1000 oe.

850@, (iQQoe, 550c*, 520oe, and the squareness ratio (Br/as) was 0.9 to 0.7. The saturation magnetic flux density was 13500 Gauss.

Example 5 Same as Example fi11 except that the area ratio Co of CO and Pt
/Pt=15.24, the cobalt alloy thin film containing 7% platinum was
Samples were prepared by depositing each film with a film thickness of 0A. The hysteresis characteristic of each sample is an anti-magnetic wheel of 500 oe.

400w, 320ae, 300oe, 300oe)
Squareization (Br/Bs) was between 0.8 and 0.6. The saturation magnetic flux density was 14,000 Gauss.

Comparative Example 1 Same as Example 1 except that the area ratio of Co and Pt was changed to CO/P.
Cobalt alloy thin film containing platinum 591 as i-21,79, 501.300, 5ooi, xsooA, 300
Samples were prepared by depositing each film with a film thickness of 0. The hysteresis characteristic of each sample has an exit rate of 200 ae.

150cm, 120ω, 120mm, 120cm, and the squareness ratio (Br/Bs) is 0.6 to 0.゛5 The saturation magnetic flux density is 14200 Gauss.

Comparative Example 2 Same as Example 1 except that the area ratio of CO and Pt was changed to Co/P.
With t=1.15, 50% of cobalt alloy thin film containing 50% of platinum! , 300 large, 900X, tsoo large, 3000
Samples were made by depositing each film with a film thickness of 100%.

Hysteresis of each sample: Characteristics are 200 gloss.

150 ae, 120 oe, 120 ce,
120 ae and saturation magnetic flux density is 7500 Gauss
It was s.

Comparative Example 3 Same as Example 1 except that the area ratio of CO and pt was changed to Co/P.
Assuming t=0.76, the cobalt alloy thin film containing 60 platinum is 50, 300, 900! , 1800 large, 3000
Samples were made by depositing each with a film thickness of ＾. The hysteresis characteristic of each sample was 200 oe.

150th, 120th, 120th, and 120th, and the saturation magnetic flux density was 6300 Gauss.

From the above results, it was found that a cobalt alloy thin film containing 7 to 40 atomic percent of platinum can be used as a magnetic storage medium. In addition, the samples of Examples 1 to 5 and Comparative Examples 1 to 3 were crushed in 23° C. ion-exchanged water to examine the state of corrosion. Figure 4 shows the rate of change in saturation magnetic flux density with immersion time.

Samples with a platinum content of 7 atomic percent or more begin to show improvement in corrosion resistance, and from 10 atomic percent to 20 atomic percent, a considerable improvement in corrosion resistance is observed. It was found that cormorant erosion does not occur at all when the concentration is 25 atomic percent or more.

As described above, it has been found that a cobalt alloy thin film containing 7 to 40% platinum has excellent magnetic properties and corrosion resistance as a magnetic storage medium.

As a result of the composition analysis of the above-mentioned sample XMA, it was found that the composition was completely consistent with the 9 composition calculated from the target area ratio, and that the composition was sufficiently uniform.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the change in coercive force depending on the atomic percentage of platinum in cobalt in a magnetic storage medium. FIG. 2 is an explanatory diagram showing the change in saturation magnetic flux density depending on the atomic percentage of platinum in cobalt in a magnetic storage medium. FIG. 3 is an explanatory diagram showing a change in coercive force depending on the film thickness of a cobalt-platinum alloy in a magnetic storage medium. FIG. 4 is an explanatory diagram showing the rate of change in saturation magnetic flux density of a magnetic storage medium made of a cobalt-platinum alloy depending on the immersion time in water. Dirt l mouth Pt gong tr %) oath yg faded one act

Claims (1)

[Claims] 1. A magnetic storage medium comprising a metal thin film, characterized in that the metal thin film contains 7 to 40 atomic percent of platinum, with the remainder being cobalt.