JPH04141817A - Perpendicular magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve C/N by first forming a thin film specified in compsn. and film thickness as an underlying layer on a film and forming a CoCr alloy thin film or a perpendicular recording layer formed by adding Ti, etc., as 3rd elements to the CoCr alloy thereon. CONSTITUTION:The thin film 2 which consists of the compsn. contg. 5 to 20wt.% Cr, 3 to 20wt.% Ni, 3 to 15wt.% Nb and the balance Co and has 200<=d<=1000[A] film thickness d is first formed on the film 1. The perpendicular recording layer 3 formed by adding the Ti, Ta, B, etc., as the 3rd elements to the CoCr alloy is formed thereon. Magnetization remains in a magnetic domain unit if magnetization inversion is recorded on the CoCr layer and, therefore, the magnetization inverted parts are not linear but zigzag. Medium noises are generated in the zigzag parts and if the width thereof is large, the noises increases and, therefore, the CoCrNiNb alloy formed by adding Nb to CoCrNi is adopted as the underlying layer t. The medium noises of the perpendicular magnetic recording medium by the CoCr alloy thin film are decreased in this way and the C/N is improved.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to perpendicular magnetic recording media.

[Prior Art] In recent years, with the demand for smaller size and larger capacity of external storage devices used in personal computers, laptop computers, etc., floppy disk type magnetic recording devices are becoming more densely packed.

This method of increasing density can be roughly divided into increasing the linear recording density by increasing the recording frequency and increasing the recording amount per track, and increasing the linear recording density by decreasing the track pitch and drag width.
There are two ways to increase the track density by increasing the number of tracks per disk.

Among these, to increase linear recording density, the use of perpendicular magnetic recording media is being considered.Compared to conventional longitudinal magnetic recording media, this medium has no demagnetizing field in principle, so the higher the density recording, the more stable the magnetization becomes. .

A feature of this method is that it can easily achieve high-density recording several times that of conventional methods.

In particular, a CoCr film that does not contain a non-magnetic material such as a binder or a CoCr film containing Ti as a third element.

Perpendicular magnetic recording media using metal thin films doped with TaPt, B, etc. are being studied.

On the other hand, the increase in track density is about 100% compared to the conventional one.
When the floppy disk driver exceeds 200 [TPI], which is about twice that of [TP1], servo control of the head is required on the floppy disk driver side. 500
Devices with [TPI] are being put into practical use in the longitudinal magnetic recording system, and floppy disk-type magnetic recording devices with a storage capacity of about 5' times that of conventional ones have appeared.

Therefore, if it is possible to increase the linear recording density and track density by using a perpendicular magnetic recording medium made of a thin metal film, a floppy disk type magnetic recording device with a storage capacity several tens of times larger can be obtained.

It is known that the relationship between track width and playback output is almost proportional, and when the track width is narrowed to increase track density, the playback output decreases. Therefore, in order to improve the track density of a floppy disk, it is necessary to increase the output to compensate for the decrease in reproduction output due to the reduction in track width.

However, the re-output power of a perpendicular magnetic recording medium made of a CoCr alloy thin film is only about 2 dB higher than that of a conventional metal-coated medium.

Therefore, an underlayer having an axis of easy magnetization in the in-plane direction is formed between the CoCr layer and the base film.

The demagnetizing field is removed and the magnetic path between the recording layer and the underlayer becomes a so-called horseshoe-shaped closed magnetic path, improving the recording and reproducing efficiency and increasing the reproducing output.

In particular, it has been previously discovered that the reproduction output can be improved to about 8 dB by providing an underlayer made of a CoCrNi alloy.

[Problem to be Solved by the Invention] However, although the effect of the CoCrNi underlayer increases the output greatly, the medium noise also increases at the same time.

The amount of increase in media noise is about 6 dB, and the increase in C/N is only 2 dB at most. This large medium noise has been an obstacle to practical application.

Therefore, in view of the above drawbacks, the technical problem of the present invention is to
An object of the present invention is to provide a CoCr perpendicular magnetic recording medium with a large N content.

[Means for Solving the Problems] According to the present invention, in a magnetic recording medium in which a dimagnetic thin film is formed on a polymer film, first, a base layer is formed on the film with two compositions: 5 to 20 wt% Cr, N. i 3
~20wt%, Nb3~15wt%CO remaining, a thin film with a thin thickness d of 200≦d≦1000 [A] is formed, and a CoCr alloy thin film or a CoCr alloy with Tl as a third element is formed thereon.

A perpendicular magnetic recording medium characterized by forming a perpendicular recording layer doped with Ta, Pt, B, etc. is obtained.

In the present invention, by adding Nb to CoCrNi,
The magnetic domain is smaller than that of CoCrNi, reducing media noise. [Function] When magnetization reversal is recorded in the CoCr layer, magnetization remains in each magnetic domain, so as shown in Figure 2, the magnetization reversal part It will not be a straight line but a zigzag pattern. Media noise occurs in this jagged portion, and the larger the width, the larger the noise. Therefore, the larger the magnetic domain of the CoCr layer, the wider the width and the greater the medium noise.

Since CoCr is epitaxially grown on the CoCrNi underlayer, the size of the magnetic domain of CoCr depends on the size of the magnetic domain of the CoCrNi layer. This CoCr
This is because the magnetic domain of Ni is large.

Media noise was getting louder.

Therefore, if a material with a small magnetic domain is used as the underlayer, medium noise can be reduced.

As a result of intensive studies regarding the above points, the present inventor has found that CocrN
It has been found that by employing a CoCrNiNb alloy in which Nb is added to i as the underlayer, it is possible to reduce the medium noise of a perpendicular magnetic recording medium using a CoCr alloy thin film.

Comparative Examples and Examples will be described in detail below. [Comparative Example] C was coated with a thickness of 500 [A] on a polyimide film with a thickness of 30 μm by an RF magnetron method.

A CrNi underlayer was formed, and a 0.3 μm CoCr thin film was further formed thereon. At this time, the sputtering pressure for both types of thin films was 0.1 [Pa], and the RF power density was 2.74 [W/c].

Also.

CoCr target composition is 17.5wt%:Cr.

What is the composition of the CoCrNi target?

Cr: 10wt%, Ni: 10wt% And so.

[Example 1] In a comparative example, CoCrNi underlayer was replaced with Co
With a target made of CrNiNb alloy, 500
[A CoCrNiNb underlayer having a thickness of A was formed, and then a CoCr film was formed in the same manner as in the comparative example. Co at this time
The target composition of the CrNiNb underlayer is Cr: lQwi%, Ni: 10wt%.

Nb: 3wt% And so.

[Example 2 In Example 1, the composition of the CoCrNiNb underlayer was Cr: 10wt%, Ni: 10wt%.

Nb: 5wt% 2 were made as follows.

[Example 3 In Example 1, the composition of the CoCrNiNb underlayer was Cr: 10wt%, Ni: 10wt%.

Nb: 10wt% One was made as follows.

[Example 4] In Example 1, the composition of the CoCrNiNb underlayer was Cr: 10wt%, Ni: 10wt%.

Nb: 15wt% One was made as follows.

[Example 5] In Example 1, the composition of the CoCrNiNb underlayer was Cr: 10wt%, Ni: 10wt%.

Nb: 20wt% 2 were made as follows.

For the above comparative examples and examples, a carbon protective film with a thickness of 100 [A] was formed and punched into a 2-inch size to form a 2-inch data disk, and the electromagnetic conversion characteristics were evaluated.

The head at this time was an MIG type bulk head with a gap length of 0.15 μm, and the measurement was performed at a radius of 20+++ m.

Figure 3 shows a commercially available metal coating medium (VF-1 Hitachi Maxell ■
C/N of 10 MHz in Comparative Example and Example 3
shows. Figure 4 shows 10 [M
Relationship of playback output in Hzl and 11[
The relationship between media noise in MHzl is shown. However, the output or noise of a commercially available metal coating medium was expressed as OdB.

Over the examples, the output was larger than that of commercially available metal coating media, especially for examples 3 to 15 [wt%].
In the case of rNi underlayer (Nb content 0wt%), the relative noise level is about 4 to 5 dB lower, and compared to commercially available metal coating media, it is only about 1 to 3 dB higher, so the C/N is Increases by 4-6dB.

We also investigated changes in reproduction output and media noise with respect to the Ni and Cr contents of the CoCrNiNb underlayer.

[Example 6 In Example 1, the composition of the CoCrNiNb underlayer was Cr: 10wt%, Ni: 3wt% Nb: 10wt% One was made as follows.

[Example 7] In Example 1, the composition of the CoCrNiNb underlayer was Cr: 10wt%, Ni: 5wt%.

Nb: 10wt% It was created as

[Example 8] In Example 1, the composition of the CoCrNiNb underlayer was Cr: 10wt%, Ni: 20wt%.

Nb: 10wt% One was made as follows.

[Example 9 In Example 1, the composition of the CoCrNiNb underlayer was Cr: 10wt%, Ni: 30wt%.

Nb: 10wt% One was made as follows.

[Example 10] In Example 1, the composition of the CoCrNiNb underlayer was Cr: 5wt%, Ni: 1Qwt% Nb: lQwt% It was created as

[Example 11] In Example 1, the composition of the CoCrNiNb underlayer was Cr: 15wt%, Ni: 10wt%.

Nb: 10wt% One was made as follows.

[Example 12] In Example 1, the composition of the CoCrNiNb underlayer was Cr: 20wt%, Ni: 10wt%.

Nb: 10wt% One was made as follows.

[Example 13] In Example 1, the composition of the C0CrNiNb underlayer was Cr: 25 wt%, Ni: 10 wt%.

Nb: 10wt% One was made as follows.

Similar to FIG. 4, the relationship between Ni content or Cr content, reproduction output, and medium noise is shown in FIGS. 5 and 6, respectively.

It can be seen that when the Ni content is 3 to 20 wt% and the Cr content is 5 to 20 wt%, the reproduction output is large and the difference in medium noise from the metal coated medium is also small.

From the above examples, the composition of the CoCrNiNb underlayer is as follows.

Cr 5-20 wt%, Ni 3-20 wt%.

It can be seen that when Nb3 to 15 wt% Co remains, the medium noise can be reduced by about 3 to 5 dB compared to the case of the CoCrNi underlayer, and the C/N increases by 5 to 7 dB compared to the metal coated medium.

On the other hand, changes in reproduction output with respect to the thickness of the CoCrNiNb underlayer were also investigated.

[Example 14] In Example 3, the thickness of the CoCrNiNb underlayer was 1
00[It was set as A.

[Example 15] In Example 3, the thickness of the CoCrNiNb underlayer was changed to 2.
00[It was set as A.

[Example 16] In Example 3, the thickness of the (0(rNiNb underlayer) was
00 [A].

[Example 17] In Example 3, the thickness of the CoCrNiNb underlayer was changed to 4
00 [A].

[Example 18] In Example 3, the thickness of the CoCrNiNb underlayer was 8
00 [A].

[Example 19] In Example 3, the thickness of the CoCrNiNb underlayer was 1
000[A co.

[Example 20] In Example 3, the thickness of the CoCrNiNb underlayer was 1
500 [A co.

Regarding Example 3 and Examples 14 to 20 above.

FIG. 7 is a graph showing the relationship between the thickness of the C0CrNiNb underlayer, reproduction output, and medium noise.

It can be seen that the medium noise gradually increases as the thickness increases, but it shows a nearly constant value when the reproduction output is between 200 and 1000[A], and the C/N is also large.

Here, in the second embodiment of the present invention, a 2-inch data floppy disk has been described, but floppy disks of other sizes may be used, and the same effect can be obtained even with a tape. The invention is not limited to the embodiments.

[Effects of the Invention] As described above, according to the present invention, a CoCr perpendicular magnetic recording medium with low medium noise and high C/N can be manufactured.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the present invention. Figure 2 is. FIG. 2 is a schematic diagram illustrating the magnitude of medium noise. Figure 3 is 1
Examples and comparative examples of the present invention, C/ of commercially available metal coating media
It is N. FIG. 4 shows the relationship between Nb content, reproduction output, and medium noise in one embodiment of the present invention. Figure 5 is 2
In the present invention, there is a relationship between Nl content, reproduction output, and medium noise. FIG. 6 shows the relationship between Cr content, reproduction output, and medium noise in one embodiment of the present invention. Figure 7 is. In the embodiment of the present invention, there is a relationship between the CoCrNiNb film thickness, reproduction output, and medium noise. 1...Base film, 2...CoCrN13...
- Perpendicular recording layer, 4...protective/lubricant layer. Nb layer. 1tff people

Claims (1)

[Claims] 1. In a magnetic recording medium in which a magnetic thin film is formed on a polymer film, an underlayer is first formed on the film with the following compositions: 5 to 20 wt% Cr, 3 to 20 wt% Ni, and 3 to 1 Nb.
Form a thin film with 5 wt% Co remaining and a thickness d of 200≦d≦1000 [A], and add Ti, Ta, Pt, B, etc. as a third element to the CoCr alloy thin film or CoCr alloy on top of it. 1. A perpendicular magnetic recording medium characterized by forming a perpendicular recording layer.