JPH02187916A - Perpendicular magnetic recording medium and production thereof - Google Patents

Abstract

PURPOSE:To increase the thickness of a target and duration for sputtering by using such a target comprising specific metal and specific metal oxide. CONSTITUTION:The perpendicular magnetic anisotropic film of this medium consists of partially oxidized Co or partially oxidized Fe-Co. This film is formed by using a target comprising one or more material selected from Co, mixture of Fe and Co and Fe-Co alloy and one or more material from Fe oxide or Co oxide, by high frequency magnetron sputtering method. Oxides of Co or Fe (e.g. FeO powder) are preferably used for the target. This target requires no frequent change, which reduces the cost for the target.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a perpendicular magnetic recording medium capable of high-density recording and a method for manufacturing the same. More specifically, the present invention relates to a perpendicular magnetic recording medium suitable for flexible disks, magnetic tapes, and hard disks, and a method for manufacturing the same.

[Conventional technology]

Conventionally, Co partial oxide thin films, Fe--Co alloy partial oxide thin films, and the like have been proposed as perpendicular magnetic recording media capable of high-density magnetic recording. The image area oxide thin film has a large perpendicular magnetic anisotropy, allowing high-density recording, and since it is composed of oxide, it is hard and exhibits excellent wear resistance against head sliding.

These partial oxide thin films can be produced by vacuum evaporation in an oxygen atmosphere or reactive sputtering in an oxygen atmosphere.

[Problem to be solved by the invention 3. In the case of reactive sputtering, there is a problem that distribution of magnetic properties and film thickness tends to occur. 6. In reactive sputtering, the deposition of the film and the reaction with oxygen compete with each other. It is absolutely necessary that the deposition rate be uniform. If oxygen supply is uniform over the substrate surface, the oxidation rate will be high in areas where the deposition rate is slow. In the case of a partially oxidized perpendicular magnetization film, the oxidation rate has a large effect on the magnetic properties, and if the oxidation rate is non-uniform, a uniform magnetic film cannot be obtained. Therefore, it is recommended to shield the parts with a slow deposition rate with a shield plate, etc.
However, if the target is shielded, the effective utilization rate of the target will be greatly reduced. Furthermore, it is quite difficult to uniformly supply oxygen to a wide substrate.

Therefore, the magnetic film made by reactive sputtering is
Generally, there is a distribution in magnetic properties and film thickness, and from the viewpoint of the recording medium, this leads to undesirable conditions such as variations in reproduction output.

In addition, in the sputtering method, it is common to use the magnetron sputtering method to increase the deposition rate, but metal targets such as Fe-Co alloy and Co have large saturation magnetization and magnetic flux is absorbed into the target. and the leakage magnetic field necessary to maintain the magnetron discharge is insufficient. Therefore, a strong magnet must be used and the target must be thin. However, there is a limit to increasing the strength of the magnet, and thinning the target shortens its duration, making it necessary to replace the target frequently, which increases the cost of the target and reduces productivity. There is a problem.

[Means for solving problems]

In view of the above-mentioned circumstances, the present inventors have conducted intensive research to solve the above-mentioned problems, and as a result, have arrived at the present invention.

That is, the first aspect of the present invention is to provide, on a substrate, at least one metal selected from cobalt, a mixture of iron and cobalt, and an iron-cobalt alloy, and an oxide of iron and an oxide of cobalt. A magnetic recording medium is provided with a perpendicular magnetic anisotropic film made of a cobalt partial oxide or an iron-cobalt partial oxide formed by a sputtering method using a target made of at least one metal oxide. The second aspect of the present invention is that when producing a perpendicular magnetic recording medium made of cobalt partial oxide or iron-cobalt partial oxide, at least one metal selected from cobalt, a mixture of iron and cobalt, and an iron-cobalt alloy is used. and at least I selected from oxides of iron and oxides of cobalt.
, fffi metal oxide, and a method for manufacturing a perpendicular magnetic recording medium characterized in that the recording medium is manufactured by a sputtering method using a target composed of metal oxides of , and fffi.

The magnetic recording medium of the present invention is manufactured by a sputtering method, and it does not matter whether the method is a direct current method or a high frequency method.

The target used in the present invention is composed of a mixture of metal and oxide. At least one metal is selected from Co, a mixture of Fe and Co, and a Fe-Co alloy. As the oxide, an oxide of Fe and an oxide of Co are used, and more specifically, Fed, Fe2O3,
At least one kind is selected from iron oxides such as FeJa and cobalt oxides such as COO and CO104. In particular, Co
and FeO, Co and CoO, Co--Fe alloy and FeO, etc. are typical preferred combinations. Since a magnetic film with a composition extremely close to the target composition can be obtained by sputtering, the mixing ratio of metal and oxide is an important factor in determining magnetic properties, especially saturation magnetization. The target is manufactured by mixing the two powders and molding them under pressure.

A target made of such a partial oxide is naturally conductive and can be used not only for high frequency sputtering but also for direct current sputtering. Also, compared to the ferromagnetic metal target used in reactive sputtering, the
There are great advantages in that the magnetic flux is small, the leakage magnetic field from the lower magnet is strong during magnetron sputtering, and therefore a thick target, for example 5 dragons or more, can be used.

Regarding the sputtering conditions, there is no difference from ordinary, for example, reactive sputtering using a metal target. The substrate has a thickness of 5 μm to several cranes,
An organic polymer type plate, sheet or film such as polyester or polyimide, a metal plate such as aluminum or stainless steel, a glass plate, etc. can be used.

Regarding the manufacturing method of the Pe-Co alloy or Co partial oxide perpendicular magnetization film, the substrate temperature is 0 to 200°C, the argon gas pressure is 1 to 10 mTorr, and the film forming rate is 100 to 100 mTorr.
It is suitably produced under conditions of 0.00 people/minute. Fe-Co-0
In the production of perpendicular magnetization films, Fe and C are used.

When the composition is 30 to 70 atomic percent Co, a medium with large perpendicular magnetic anisotropy and high read sensitivity when recorded and read using a ring head can be obtained. There is a nearly linear relationship between the oxygen content and the saturation magnetization of the resulting magnetic film. Therefore, the saturation magnetization is determined by the mixing ratio of the target metal and oxide. Saturation magnetization is 300 to 950 emu
/cJ shows large perpendicular magnetic anisotropy, high reproduction output, and high recording density characteristics. Especially from 500
A region of 900 emu/c+J is preferable. If the saturation magnetization is lower than this value, the reproduction output will decrease, and if it is higher than this value, the recording density will decrease.
7kOe, vertical coercive force (He) 200-10000e
A perpendicularly magnetized film is obtained.

Note that even when performing sputtering using a partial oxide target, it is possible to further introduce oxygen gas. By introducing #I elementary gas, the oxygen content can be increased and the saturation magnetization can be lowered. Even in this case, the advantages provided by using a partial oxide target are maintained.

The thickness of the Fe-Co-0 or Co-0 perpendicular magnetic anisotropic film is preferably 500 to 6,000, particularly 700 to 3,000. If the thickness is less than this, both the reproduction output voltage and the recording density will decrease, and if it is more than this, the reproduction output voltage and recording density will decrease. That would be uneconomical.

In sputtering a partial oxide target, a film with a composition equal to that of the target is obtained, and the escape of oxygen bones is small. Therefore, the oxygen content is constant throughout the substrate, and the uniformity of the magnetic properties is extremely good. This point is superior to reactive sputtering, in which the oxidation rate differs due to the difference in deposition rate, and the magnetic properties exhibit a wide distribution.

Ni+ Cr, AI+ Z in partial oxide target
10% by weight of third elements such as r, Nb, and their oxides
It is not a problem to include the following, but it is preferable to improve the corrosion resistance of the medium.

(Examples) Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited by these in any way.

Example 1 Fe0 powder and Co powder were mixed at a molar ratio of 4:6, and a target having a diameter of 6 inches and a thickness of 5 mm was prepared by pressure molding, and the target was attached to a copper banking plate using solder.

An Fe-Co-0 perpendicular magnetization film was fabricated on a polyimide film having a thickness of 50 μm by high-frequency magnetron sputtering. The polyimide film was attached to the substrate holder with enough tension to prevent the film from sagging. It is a sputter-up method.

The distance between target substrates is 72 cranes. Ultimate vacuum level 7
X 10-'Torr of fulbone gas at 10C
CI11 was introduced, the valve opening was adjusted to 2III Torr, and sputtering was performed at 900 W for 2 minutes. At that time, the substrate holder was water-cooled.

The distribution of magnetic properties in the radial direction of the obtained recording medium was measured. The results are shown in Table 1.

Table 1 From Table 1, it is known that when a partial oxide target is used, although there is a thickness distribution in the radial direction, there is almost no distribution of magnetic properties.

Furthermore, floppy disks were cut out and the recording resuscitation durability was measured. The head used was a Mn--Zn ferrite ring head used in video tape recorders.

The measurement was performed at a gap length of 0.35 microns, a trunk width of 30 microns, a coil winding number of 20 turns, and a running speed of 2 m/s. Normalized playback output 30 μ at a radius of 4.2 cm
■. -p /mm/(m/5e-c)/1urns The recording density is such that the playback output is halved.

is 79kFCI (Flux Change per
Inch).

Comparative Example 1 Sputtering was attempted under the same conditions using the same equipment as in Example 1, except that a target of 6 inches in diameter and 2 mm in thickness made of Fe-Co alloy with a molar ratio of 4:6 was used. , the leakage magnetic field was small and sputtering could not be performed.

Comparative Example 2 A polyimide film was sputtered using a target with a diameter of 6 inches and a thickness of 1 mm made of a Pe--Co alloy with a molar ratio of 4:6. Argon gas was introduced at 10ccm and the valve opening was adjusted to 2 mTorr.

Furthermore, 7.5 ccm of oxygen was introduced. Fe-Co was sputtered for 1.5 minutes at 900W in the same manner as in Example 1.
A -0 perpendicular magnetization film was produced. The results are shown in Table 2.

Table 2 From Table 2, it can be seen that the distribution of magnetic properties in the radial direction is larger than in Example 1.

Furthermore, recording and reproducing characteristics were measured in the same manner as in Example 1.

Normalized playback output at a radius of 3cm is 32μVo-a
/mm/(m/5ee)/1urn,, Dso is 78
It was kl'CI.

Example 2 Sputtering conditions were set in the same manner as in Example 1, except that a DC power source was used as the power source. That is, 560 ■ is 1.
Five people sputtered for 2 minutes.

The magnetic property at a position with a diameter of 5.5 cm is saturation magnetization of 64.0.
emu/cj, perpendicular anisotropic magnetic field 3.5 kOe, coercive force 3
000e, and the film thickness was 2570 people. As for the recording and playback characteristics, the normalized playback output is 28μVo-p/mm/(m
/5ec)/Lurn.

D. was 65kPCI.

Examples 3 to 5 Fe-Co-0 perpendicular magnetization films were obtained in the same manner as in Example 1 except that the sputtering power and time were changed. The feel of the obtained recording medium at radius 5 (J) is shown in Table 3.

It is known that the magnetic properties are almost constant regardless of the power. In the case of reactive sputtering, it is necessary to increase the amount of oxygen introduced as the power is increased.

Table 3 The spankling method for obtaining a partially oxidized perpendicular magnetic anisotropic medium using the partially oxidized target of the present invention uses a ferromagnetic metal target to produce a partially oxidized perpendicular magnetic anisotropic medium without introducing oxygen.
Compared to the reactive sputtering method to obtain a gas anisotropic medium, the target can be made thicker and last longer (which not only reduces target cost but also improves productivity). The medium has excellent uniformity of magnetic properties.

[Action/Effect]

Claims (3)

[Claims] 1. On the substrate, at least one metal selected from cobalt, a mixture of iron and cobalt, and an iron-cobalt alloy, and at least one metal oxide selected from iron oxide and cobalt oxide. 1. A magnetic recording medium provided with a perpendicular magnetic anisotropic film made of a cobalt partial oxide or an iron-cobalt partial oxide formed by a sputtering method using a target comprising: 2. 2. The magnetic recording medium according to claim 1, wherein the target is composed of cobalt and iron oxide. 3. In producing a perpendicular magnetic recording medium made of cobalt partial oxide or iron-cobalt partial oxide, at least one metal selected from cobalt, a mixture of iron and cobalt, and an iron-cobalt alloy, iron oxide and A method for manufacturing a perpendicular magnetic recording medium, characterized in that the recording medium is manufactured by a sputtering method using a target made of at least one metal oxide selected from cobalt oxides.