JPH0460918A - Perpendicular magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a medium having stable reproducing output with food reproducibility be forming a base layer comprising Cr under a CoCrNi alloy layer. CONSTITUTION:A Cr film is formed as the first layer 3 to thickness d1 satisfying 0.1<=d1<=0.3 (mum). A CoCrNi film having the compsn. (Co82.5Cr17.5)100-xNix, wherein 2<=x<=50 (wt.%), is formed as the second layer 2 to the thickness d2 satisfying 200<=d2<=1,000 (Angstrom ), and a perpendicular recording layer comprising a CoCr alloy thin film or CoCr alloy with addition of Ti, Ta, Pt, B, etc., as the third element is formed to thickness d3 of 0.01<=d3<=0.5 (mum) as the third layer 1. Thereby, the CoCr perpendicular magnetic recording medium with higher reproducing output can be stably formed.

Description

[Detailed Description of the Invention] [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., high-density floppy disk type magnetic recording devices have been developed. is being developed.

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;
There are two ways to increase the track density by narrowing the track pitch and track width to increase the number of tracks per disk.

Among these, to increase the linear recording density, the use of perpendicular magnetic recording media has been considered, and some coated disks made of barium ferrite have been put into practical use.

This is because, compared to conventional longitudinal recording media, there is no demagnetizing field in principle, so the higher the recording density, the more stable the magnetization becomes, and the higher the density recording, the higher the recording density than in the past.

In order to further improve the linear recording density, a perpendicular magnetic recording medium using a CoCr film or a metal thin film in which Ti, Ta, PtB, etc. are added as a third element to CoCr, which does not contain a non-magnetic material such as a binder, is being considered. It is progressing.

1/,',I- Regarding the increase in rack density, the increase in rack density is about 2 (10 [TP
I], servo control of the head is required on the driver side of the floppy disk, and development for this is progressing, and those with a TPI of 400 to 500 that adopt this servo control system are the longitudinal recording system. A floppy disk-type magnetic recording device with a storage capacity about five times that of the conventional device has appeared.

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

On the other hand, regarding tape media such as VTR,
If dramatically high-density recording becomes possible, high-definition VTRs, which are currently only commercially available, will become technically viable for consumer use.

It is known that the relationship between track width and reproduction output is almost proportional, and if the track width is narrowed to increase track density, the reproduction output will decrease. Therefore,
In order to improve the track density of a floppy disk, it is necessary to increase the output to compensate for the 1'1' decrease in reproduction output caused by the reduction in track width.

On the other hand, regarding tape media such as VTR,
When attempting to utilize the advantage of perpendicular magnetic recording media, which allows high-density recording, recording and reproduction are performed over a wide band of frequencies, so high output is required to ensure S/N.

[Problem to be solved by the invention] However, because the reproduction output of a perpendicular magnetic recording medium made of two series of CoCr alloy thin films is only about 2 dB higher than that of a coated medium made of conventional metal magnetic powder. This required the development of a new low-noise reproduction amplifier and signal processing circuit, which was a major obstacle to practical application.

For this reason, the inventor previously proposed that C.
It has been found that by providing the oCrNi underlayer, the reproduction output can be increased by approximately 6 dB due to the vertical alignment layer and the underlying in-plane orientation layer.

This takes advantage of the fact that the axis of easy magnetization of the CoCrNi film is in the in-plane direction, and the recorded magnetization becomes horseshoe-shaped, resulting in a reduction in magnetic resistance and an increase in the recorded magnetic energy. be.

At this time, the direction of the magnetization container axis of the CoCrTi layer is closely related to the Ni content, and as shown in FIG. 3, as the Ni content increases, the squareness ratio in the in-plane direction becomes more opposite.

As shown in FIG. 4, the medium noise during 1/J% reproduction increases as the Nl content increases.

Therefore, if the Ni content in the CoCrNi layer is too high, it will increase the medium noise, and if it is too low, it will not have an axis of easy magnetization in the in-plane direction, which will reduce the reproduction output.

That is, since the C/N ratio changes greatly due to slight changes in the Ni layer of the CoCrNi layer produced, there is a drawback that stable media production is difficult.

SUMMARY OF THE INVENTION In view of the above drawbacks, the technical object of the present invention is to provide a C0Cr perpendicular magnetic recording medium that can significantly increase the reproduction output.

[Means for solving the problem] According to the present invention, in a magnetic recording medium in which a magnetic thin film is formed on a polymer film, the first layer has a thickness do of 0.1≦d1≦0.3 ( μl11) A Cr film is formed as the second layer, the film thickness d2 is in the range of 200≦d2≦1000 [people], and the composition is (CO825' Cr 1t, ++) ton-
x −N ix : 2≦X≦50 [wt
%], and as the third layer, a CoCr alloy thin film or CoCr alloy with a thickness d3 of 0.01≦d3≦0.5 (μl11) was added with Ti, Ta5PtSB, etc. as a third element. A perpendicular magnetic recording medium characterized in that a perpendicular recording layer is formed is obtained.

In order to solve the above problems, the present inventors have discovered that by further providing a base layer made of Cr under the CoCrNi alloy layer, a medium with stable reproduction output can be produced with good reproducibility.

[Effects] Since the perpendicular orientation of the magnetization of the CoCr film is due to the magnetocrystalline anisotropy due to the hcp structure, CoCr is used as the underlayer.
By forming a CoCrNi film having approximately the same lattice spacing as the film, horseshoe-shaped magnetization can be formed without impairing the vertical orientation of the CoCr film.

Here, as a result of intensive study, the present inventor found that in order to reduce the amount of Ni in the CoCrNi film and ensure the inner orientation,
It has been found that it is sufficient to form a Cr film under the CoCrNi film.

That is, as shown in FIG. 1, the perpendicular magnetic recording medium has a structure in which a Cr film is formed as the first layer and a Cr film is formed as the second layer.
The structure is such that an in-plane alignment layer made of an oCrNi film is formed, and a perpendicular recording layer typified by CoCr is formed as a third layer.

[Embodiments] Next, embodiments of the present invention will be described with reference to the drawings.

[Comparative Example 1] A polyimide film with a thickness of 500 μm was coated with a target made of a CoCrNi alloy by the RF magnetron method.

A CrNi underlayer is formed, and then a 0.3μ thick Co
A Cr thin film was formed. The sputtering pressure at this time was 0.1
[Pa], and the RF power density is 2.74 [W
/c].

8.1 The target composition of the CoCrNi underlayer at this time is (C082,5Cr 17.5) +00-X N i
x: X=5[vt%]. Also, the CoCr target composition is 17.5wt
%: Cr.

[Comparative Example 2] A Cr thin film having a thickness of 2500 mm was formed on a base film, and a CoCr film was formed thereon.

This sputtering pressure is 0.1 for both Cr-CoCr.
[Pa], and the RF power density is 2.74 [W
/eJ].

[Example 1] In a comparative example, a C film having a thickness of 500 cm was formed under a CcjCrNi underlayer.

[Example 2] In Example 1, the film thickness of the Cr layer was set to 1000 [8].

[Example 3] In Example 1, the thickness of the Cr layer was set to 1500 [8].

[Example 4] In Example 1, the thickness of the Cr layer was set to 2000 [people].

[Example 5] In Example 1, the thickness of the Cr layer was set to 2500 mm.

[Example 6] In Example], the film thickness of the Cr layer was set to 3000 [Å].

[Example 7] In Example 5, the target composition of the CoCrNi layer was (Coll+25cr 17.5) too-X N
ix: X=10 [v1%].

[Example 8] In Example 5, the target composition of the CoCrNi layer was (C082,5Cr 17.5) +00-X N i
x: X=15 [νt%].

[Example 9] In Example 5, the target composition of the CoCrNi layer was (C082,5Cr 17.5) too-X N i
X: X=20 [wt%].

For the following Comparative Examples and Examples, a carbon protective film with a thickness of 100 [man] was formed and punched into 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+n.

FIG. 5 shows the relationship between reproduction output and medium noise (8MIIz) during 9Ml1z recording when the Cr film thickness was changed for Comparative Example 1 and Examples 1 to 6.

Since the noise level depends on the amount of Nl in the CoCrNi layer, it is unaffected by the thickness of the Cr layer and remains almost constant, but the reproduction output increases up to a Cr film thickness of 1000 mm and above that. is saturated, and the Cr layer thickness is 10
It can be seen that it is sufficient if the thickness is 00 Å or more.

Further, FIG. 6 shows the relationship between the reproduction output at 9 MHz and the medium noise at 8 MHz when the Ni concentration of the CoCrNi layer is changed for Comparative Examples 1 to 2 and Examples 5 and 7 to 9.

Here, the Ni concentration O [wL%] in Comparative Example 2 is
These are measurement results for a medium having a structure without a CoCrNi film.

It can be seen that by providing the Cr layer, high reproduction output and low medium noise can be achieved even at a low N i of 41 degrees.

[Effects of the Invention] As described above, according to the present invention, a CoCr perpendicular magnetic recording medium with significantly increased reproduction output can be stably manufactured.

Here, in the 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 present invention is not limited to this embodiment.

FIG. 1 is a schematic diagram of the invention.

FIG. 2 is a schematic diagram of a conventional example.

FIG. 3 is a graph showing the relationship between the amount of Ni in the CoCrNi layer and the squareness ratio/reproduction output in a conventional example.

FIG. 4 is a graph showing the relationship between the amount of Ni in the CoCrNi layer and the media noise in the conventional example.

5 and 6 are examples of the present invention.

DESCRIPTION OF SYMBOLS 1... Perpendicular recording layer, 2... In-plane alignment layer, 3... C
r base layer, 4... base film, 5... lines of magnetic force,
6...Magnetization.

Cause of size ■

Claims (1)

[Claims] 1) In a magnetic recording medium in which a magnetic thin film is formed on a polymer film, the thickness d_1 of the first layer is in the range of 0.1≦d_1≦0.3 (μm). A Cr film is formed, a CoCrNi film is formed as the second layer, the film thickness d_2 is in the range of 200≦d_2≦1000 [Å], and the composition is ▲numerical formula, chemical formula, table, etc.▼; A CoCr alloy thin film with a thickness d_3 of 0.01≦d_3≦0.5 (μm) or a perpendicular recording layer formed by adding a third element such as Ti, Ta, Pt, or B to a CoCr alloy is formed as a layer. Features of perpendicular magnetic recording media.