JPS6136290B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic disk device, and particularly to a magnetic disk and a method for manufacturing the same.

At present, rapid progress is being made in improving the recording density and writing/reading speed of magnetic disk devices. In order to achieve high-density recording, it is necessary to improve bit density (BPI) and track density (TPI), and the following related technologies have been improved. Namely, (1) the magnetic properties of the recording medium, (2) the write/read characteristics of the magnetic head, and (3)
These include technology for maintaining a minute gap between the recording medium and the magnetic head, (4) technology for accurately positioning the magnetic head on the recording track, and (5) write/read circuits including recording and reproducing methods.

In a magnetic disk, the disk rotates at high speed and a slider (magnetic head) floats due to the surface flow of air on the disk plate. Since the circumferential speed on the outside of the disk plate is faster than on the inside, the floating gap of the magnetic head is also larger. For example, the relationship between the circumferential speed and the flying height of the head is as shown in FIG. 1. Therefore, the write current applied to the magnetic head must be large on the outside of the disk and small on the inside. Furthermore, since recording is performed on the magnetic head at the same frequency, the recording density on the inner side is inevitably higher than on the outer side. The relationship between write current and output using recording density as a parameter is as shown in Figure 2, and the higher the recording density, the more optimal write current value Im.
tends to become smaller. Therefore, it is necessary to make the current smaller inside the disk than required from the relationship of the flying height. Furthermore, with a constant write current, the O/W characteristics (Over/Write characteristics, overwrite characteristics) change depending on the position of the disk, as shown in FIG. 3, and are worse on the outside of the disk than on the inside. Therefore, in conventional magnetic disk devices, the write current is changed at appropriate positions on the disk so that it is larger on the outside than on the inside. For this reason, the write circuit system has become complicated, and the output on the inside of the disk is even smaller than that on the outside due to the ratio of peripheral speed.

It is an object of the present invention to provide a magnetic disk in which the write current can be the same on the inside and outside of the disk, thereby simplifying the write circuitry.

Another object of the present invention is to relatively increase the internal output compared to conventional magnetic disks.

The above purpose is to provide a magnetic disk in which the Co content of the Co-containing iron oxide film of the magnetic recording medium decreases from the inside to the outside in the radial direction of the magnetic disk.
This is achieved by a magnetic disk characterized in that the coercive force of the magnetic recording medium on the inner side of the disk is larger than the coercive force of the magnetic recording medium on the outer side of the disk.

By increasing the coercive force of the inner magnetic recording medium of the disk according to the present invention, it is possible to increase the recording density (BPI) of the inner portion and to increase the write current, thereby increasing the output.

It is preferable that the magnetic recording medium described above is a Co-containing Fe ₃ O ₄ film or γFe ₂ O ₃ film. γFe ₂ O ₃ films generally have lower coercive force than Fe ₃ O ₄ films, but higher mechanical strength.

Further, the coercive force of a magnetic recording medium changes as shown in FIG. 4 depending on the Co content in its oxide film.
That is, as the Co content increases, the coercive force also increases. Therefore, by increasing the Co content in the magnetic medium on the inside of the magnetic disk compared to the magnetic medium on the outside, it is possible to increase the coercive force on the inside.

Another object of the present invention is to provide a method for manufacturing the magnetic disk of the present invention, in which the coercive force of the magnetic recording medium differs in the radial direction of the disk.

This objective is achieved by the following manufacturing method. That is, an αFe ₂ O ₃ film is formed on the disk substrate by sputtering an Fe target,
Next, reduce the αFe ₂ O ₃ film to form a Fe ₃ O ₄ film,
According to the present invention, in the method for manufacturing a magnetic disk in which the Fe ₃ O ₄ film is oxidized to form a γFe ₂ O ₃ film if necessary, the Fe target described above is replaced with a plurality of Fe targets having different Co contents or a plurality of Co-containing Fe targets. locally varying amounts of Fe target, and
Sputtering using Fe target, reduction,
If necessary, oxidize to remove Co in the radial direction of the disk.
This is a method for manufacturing a magnetic disk characterized by forming Fe ₃ O ₄ films or γFe ₂ O ₃ films having different contents.

It is impossible in principle to change the coercive force of a magnetic recording medium on the same disk using the film coating method or the electrodeposition method, but it becomes possible with the oxidized magnetic film using the sputtering method. This can be seen in the oxidized magnetic film that can be easily formed by changing the Co content in the Fe target used for sputtering.
This is because the coercive force can be changed by changing the Co content, and the Co content in the Fe target and the Co content in the formed oxide film are completely proportional as shown in FIG.

For example, the present applicant has disclosed Japanese Patent Applications No. 52-085571 and No.
- There is a sputtering device proposed in 085572. It is also possible to selectively form an αFe ₂ O ₃ film or a Fe ₃ O ₄ film using these devices.

The present invention will be further explained below with reference to Examples.

Example 1 As shown in Figure 6, Fe target A containing 1 at% Co, Fe target B containing 2 at% Co, and Fe target B containing 3 at%
A Co-containing Fe target C was placed on a 14-inch disk substrate 1. 50% Ar of 2×10 ^-2 Torr
- Fe while rotating substrate 1 in 50% O ₂ atmosphere.
Targets A, B, and C alternately for 10 minutes each.
Sputtering at 1kW 3 times (90 minutes in total),
αFe ₂ O ₃ film (shaded area in Figure 6) is placed on substrate 1.
It was formed with a thickness of 0.15 μm. The obtained αFe ₂ O ₃ film
A Fe ₃ O ₄ film was formed by reduction at 300° C. in a WetH ₂ atmosphere, and the Fe ₃ O ₄ film was further oxidized in air at 300° C. to form a γFe ₂ O ₃ film. FIG. 7 shows the relationship between the coercive force of the γFe ₂ O ₃ film thus obtained and the disk position. As is clear from the figure, the inside of the disk is higher than the outside. The O/W characteristics of the obtained γFe ₂ O ₃ film depend on the write current.
At 70mA, the result is as shown in Figure 8, and records can be written to the entire disk with a constant write current.

Example 2 Fe target A containing 1 at% Co as shown in Fig. 9
, 2at% Co-containing Fe target B, and 3at% Co-containing Fe target B.
An integrated Fe target 3 was made by welding Co-containing target C with an electron beam. 2×10 ^-2 Torr
The Fe target 3 was heated for 90 minutes while rotating the same substrate 1 as in Example 1 in a 50% Ar-50% O ₂ atmosphere.
Sputtering was performed at 1 kW to form an αFe ₂ O ₃ film (shaded area in FIG. 9) on the substrate 1 to a thickness of 0.15 μm.
The obtained αFe ₂ O ₃ film was reduced at 300 °C in WetH ₂ atmosphere and further oxidized at 300 °C in air to form γFe ₂ O _3.
A film was formed. γFe ₂ O ₃ obtained in this way
FIG. 10 shows the relationship between the coercive force of the film and the disk position. As in Example 1, the coercive force is higher on the inside of the disk than on the outside.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between the peripheral speed of rotation of a magnetic disk and the flying height of the head, and Figure 2 is a diagram showing the relationship between write current and output when recording density is taken as a parameter in a conventional magnetic disk. FIG. 3 is a diagram showing the O/W characteristics depending on the disk position in a conventional magnetic disk, and FIG. 4 is a diagram showing the relationship between the Co content of the recording medium oxide film and the coercive force. , and Fig. 5 shows Fe
FIG. 6 is a diagram showing the relationship between the Co content of the target and the Co content of the formed recording medium oxide film;
The figure shows the positional relationship between the Co-containing Fe target and the disk substrate in an embodiment of the magnetic disk manufacturing method according to the present invention, and FIG. 7 shows the coercive force of the recording medium of the magnetic disk according to the present invention. FIG. 8 is a diagram showing O/W characteristics of a recording medium of a magnetic disk according to the present invention,
FIG. 9 is a diagram showing the positional relationship between the Co-containing Fe target and the disk substrate in an embodiment of the magnetic disk manufacturing method according to the present invention, and FIG. 10 is a diagram showing the recording medium of the magnetic disk according to the present invention. FIG. A...Fe target containing 1at%Co, B...2at%Co
Containing Fe target, C...Fe target containing 3 at% Co, 1, 2... Disk substrate, 3... Fe target.

Claims (1)

[Claims] 1. In a magnetic disk, Co of the magnetic recording medium
The Co content of the iron oxide film decreases from the inside to the outside in the radial direction of the magnetic disk, and the coercive force of the inner magnetic recording medium is greater than the coercive force of the outer magnetic recording medium in the radial direction of the disk. A magnetic disk characterized by its large size. 2. The magnetic disk according to claim 1, wherein the magnetic recording medium is a Co-containing Fe ₃ O ₄ film. 3. The magnetic disk according to claim 1, wherein the magnetic recording medium is a Co-containing γFe ₂ O ₃ film. 4 Sputtering an Fe target to form an αFe ₂ O ₃ film on the disk substrate, and then sputtering the Fe ₂ O ₃
In a method for manufacturing a magnetic disk in which a Fe ₃ O ₄ film is formed by reducing a film, a plurality of Fe targets having different Co contents or Fe targets having locally different Co contents are prepared, and the Fe targets are The above-mentioned sputtering and reduction are performed using
A method for manufacturing a magnetic disk, comprising forming an Fe ₃ O ₄ film on the substrate. 5 Sputter the Fe target to form an αFe ₂ O ₃ film on the disk substrate, reduce the αFe ₂ O ₃ film to form an Fe ₃ O ₄ film, and then oxidize the Fe ₃ O ₄ film. In the method for manufacturing a magnetic disk in which a γFe ₂ O ₃ film is formed by forming a γFe 2 O 3 film, the Fe target is made into a plurality of Fe targets having different Co contents or Fe targets having locally different Co contents, and the Fe target is using the sputtering, reduction and oxidation in the disk radial direction.
A method for manufacturing a magnetic disk, characterized in that the γFe ₂ O ₃ films having different Co contents are formed on the substrate.