JPH0460917A - Perpendicular magnetic recording medium - Google Patents

Abstract

PURPOSE:To remove diamagnetizing field and to increase reproducing output by forming a specified base layer thin film on a polymer film and then forming a perpendicular recording layer comprising a CoCr alloy thin film or CoCr alloy with addition of Ti, Ta, Pt, B, etc., as th third element. CONSTITUTION:A base layer thin film 2 having the compsn. of (Co82.5Cr17.5)100-xNix, wherein 2<=x<=50 (wt.%), and thickness (d) satisfying 200<=d<=1,000 (Angstrom ) is formed on a polymer film 1. Then a perpendicular recording layer 3 comprising a CoCr alloy thin film or CoCr alloy with addition of Ti, Ta, Pt, B, etc., as the third element is formed on the base layer 2. By this method, the base layer comprising an CoCrNi alloy having the axis of easy magnetization parallel to the film plane is provided under the CoCr alloy layer, and thereby, the reproducing output can be improved.

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, and increasing the linear recording density by decreasing the track pitch and track width.
There are two ways to increase the track density by increasing the number of tracks per disk.

Among these, in order 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 compared to media using the conventional longitudinal recording method.

In principle, there is no demagnetizing field, so the higher the recording density, the more stable the magnetization becomes, making it easier to record at a density several times higher than in the past.

Here, in order to further improve the linear recording density, a CoCr film or a CoCr film that does not contain a non-magnetic material such as a binder is added.
Ti, Ta, Pt, B, etc. were added as a third element. Perpendicular magnetic recording media using metal thin films are being studied.

On the other hand, the increase in track density is about 100% compared to the conventional one.
[Approximately twice the TPI] When the TPI exceeds 200, servo control of the head is required on the floppy disk driver side, and development for this purpose is underway.

400 to 500 [TPI] using this servo control method
] is being put into practical use in longitudinal recording systems, and floppy disk-type magnetic recording devices with a storage capacity about five times that of conventional ones have appeared.

Therefore, by using a perpendicular magnetic recording medium made of a metal thin film,
If we can increase linear recording density and track density,
- 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 dramatic high-density recording becomes possible, it will become technically possible for high-definition VTRs, which are currently only commercially available, and for consumer use.

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

On the other hand, regarding tape media such as VTR,
When attempting to take advantage of the high density recording of perpendicular magnetic recording media, high output is required in order to maintain S/N of 11llll, since recording and reproducing are performed at frequencies over a wide band.

[Problem to be solved by the invention] However, since the reproduction output of a perpendicular magnetic recording medium made of a conventional CoCr alloy thin film is only about 40% of the reproduction output of a conventional coated medium made of metal magnetic powder, a new method is proposed. This required the development of low-noise reproduction amplifiers and signal processing circuits, which was a major obstacle to practical application.

In view of the above drawbacks, one technical object of the present invention is to provide a CoCr perpendicular magnetic recording medium with significantly increased reproduction output.

[Means for Solving the Problems] According to the present invention, in a magnetic recording medium in which a magnetic thin film is formed on a polymer film, the polymer film has a composition (COs2.s"Cr+75) too-x"N.
ix: 2≦X≦50 [vL%], and the film thickness d is.

200≦d≦1000 [people] A thin underlayer film is formed on the thin underlayer film.

The present invention is characterized in that a perpendicular recording layer is formed by adding a third element such as Ti, Ta, Pt, or B to a CoCr alloy thin film or a CoCr alloy. A perpendicular magnetic recording medium is obtained.

That is, the present invention uses carbon having an easy axis of magnetization in the in-plane direction parallel to the film surface under the CoCr alloy layer.

The reproduction output is improved by providing a base layer made of a CrNi alloy.

[Operations] It is known that one method for improving the reproduction output of a magnetic recording medium is to reduce the magnetic resistance on the magnetic circuit.

For example, in a CoCr alloy thin film, as shown in FIG. 2, magnetization occurs on the opposite side of the magnetic head to generate a demagnetizing field, increasing magnetic resistance and lowering one reproduction output.

Therefore, the underlayer with an easy axis of magnetization in one in-plane direction is made of CoCr.
By forming it between the layer and the base film, one demagnetizing field can be removed and the reproduction output can be increased.

On the other hand, there is a problem with the crystal lattice spacing in the conditions necessary for the underlayer in the thin film formation method.

That is, the perpendicular orientation of the magnetization of the CoCr film is l + c p
This is due to the crystal magnetic anisotropy due to the structure.

If a material with a lattice spacing significantly different from that of the CoCr film is selected as the underlayer, the vertical alignment of the CoCr film will be inhibited, the magnetic properties will deteriorate, and the electromagnetic conversion properties will deteriorate.

Therefore, as the second underlayer, it is desirable to use a thin film made of a CoCr alloy to which a third element is added and which has an axis of easy magnetization in one in-plane direction.

In response to the above points, the present inventor has made the following findings after extensive study.

By adopting Ni as the third element, CoCr
We have found that the reproduction output of perpendicular magnetic recording media can be increased by using alloy thin films.

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

[Comparative Example] A CoCr thin film with a thickness of 0.3 μm was formed on a polyimide film with a thickness of 30 μm by an RF magnetron method. The sputtering pressure at this time was 0.1 [Pa], and R
The F power density is 2.74 [W/cJ].

In addition, the CoCr target composition is 17.5wt%C
It was set as r.

[In Example 1 and Comparative Example, CoCrN was added before forming the CoCr layer.
A CoCrNi underlayer with a thickness of 500 mm was formed using a target made of i alloy.

Thereafter, a CoCr film was formed in the same manner as in the comparative example. The target composition of the CoCrNi underlayer at this time was (CO82,
5Cr 17.5) +00-X'Nix:
X=2 [wt%].

Also, the sputtering pressure of the base layer was 0.1. [Pa], and the RF power density is 2.74 [W/c♂].

[Example 2 In Example 1, the composition of the CoCrNi underlayer was (CO82,5Cr+7,) +oo-x ・
Nix: 1 was prepared as X-5 [wt%].

[Example 3 In Example 1, the composition of the CoCrNi underlayer was changed to (Cosz, Cr+7,) +00-X −
One was prepared as INiX:X-10 [wt%].

[Example 4 In Example 1, the composition of the CoCrNi underlayer is as follows.

(CO82,5Cr17.5) +00-X 6 N
ix: Produced as X=20[νt%].

[Example 5] In Example 1, the composition of the CoCrNi underlayer is as follows.

(C082,5Cr 17.5) +00-X”N
One was prepared with I x .X=30 [vt%].

[Example 6] In Example 1, the composition of the CoCrNi underlayer is as follows.

(COs25Cr+7.5) 100-X “Nix
:X-40 [wL%].

[Example 7] In Example 1, the composition of the CoCrNi underlayer is as follows.

(C082,5Cr 17.5) +00-X'N
ix: 2 were prepared as X-50 [wt%].

For the above comparative examples and examples, a carbon protective film with a thickness of 100[cm] was formed, and a 2-inch size was punched out to form a 2-inch data disk.

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+ nm.

Figure 3 shows a commercially available metal medium (VF-1 manufactured by Hitachi Maxell ■)
FIG. 4 shows the recording frequency characteristics of Comparative Example and Example 2 as a function of the Ni content of the underlayer.
], and the reproduction output of the coating medium using metal magnetic powder.

-・9 1.0 All of Examples 2 to 50 [Wt96] had reproduction outputs equal to or higher than the coating media made of metal magnetic powder, especially 2
It can be seen that in the range of ~30 [wt%], there is more than twice the reproduction output.

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

[Example 8] In Example 2, the thickness of the base layer of r Co Cr N was set to 100 mm.

[Example 9] In Example 2, the thickness of the CoCrNi underlayer was 200%.
[person].

[Example 10] In Example 2, the thickness of the CoCrNi underlayer was 300 mm.
[8].

[Example 11 In Example 2, the thickness of the CoCrNi underlayer was 400 mm.
Kuchito].

[Example 12] In Example 2, the thickness of the CoCrNi underlayer was 800 mm.
[person].

[Example 13] In Example 2, the thickness of the CoCrNi underlayer was set to 100
0 [I felt depressed.

[Example 14] In Example 2, the thickness of the CoCrNi underlayer was set to 1.5
00[I made a human.

Regarding Example 2 and Examples 8 to 14 above, CoCr
FIG. 5 is a graph showing the relationship between the thickness of the Ni underlayer and the reproduction output.

It can be seen that the value is almost constant between 200[A] and 1000[A].

[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 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 an i''A tape, so the shape of the medium The present invention is not limited to the embodiments.

FIG. 1 is a schematic diagram of the invention.

FIG. 2 is a schematic diagram showing the magnetization that generates the demagnetizing field.

FIG. 3 shows the recording frequency characteristics of the present invention.

FIG. 4 shows the relationship between Ni content and reproduction output in an example of the present invention.

FIG. 5 shows the relationship between CoCrNi film thickness regeneration specific force in an example of the present invention.

DESCRIPTION OF SYMBOLS 1... Base film, 2... CO.Cr-N1 layer 3... Perpendicular recording layer, 4... Protective lubricating layer, 5... Magnetic head, 6... Magnetic charge.

Figure 3 playback output [Relative value] Recording frequency (Hz) Figure 4 playback output O Contains Yes Amount (wt%)

Claims (1)

[Claims] 1) In a magnetic recording medium in which a magnetic thin film is formed on a polymer film, the composition on the polymer film is ▲There are mathematical formulas, chemical formulas, tables, etc.▼, and the film thickness d is A thin underlayer film with the following relationship: 200≦d≦1000 [Å] is formed, and on the thin underlayer film, CoC
Ti as a third element in r alloy thin film or CoCr alloy,
A perpendicular magnetic recording medium comprising a perpendicular recording layer doped with Ta, Pt, B, etc.