JPH04206018A - Perpendicular magnetic recording medium - Google Patents

Abstract

PURPOSE:To increase the regenerative output of a perpendicular magnetic recording medium by a CoCr alloy thin-film by adopting Ni as a third element to a CoCr alloy as a foundation layer and using Ni in a large quantity in a lower layer and in a very small quantity in an upper layer at the composition ratio. CONSTITUTION:A Co, Cr, Ni thin-film, which contains 15-20wt.% Cr, 3-10wt.% Ni and Co as the remainder and in which Ni concentration is reduced extending over an upper layer from a lower layer, Ni concentration is substantially 0wt.% in an uppermost section and film thickness (d) satisfies 200<=d<=1000 [angstroms], is formed onto a film 4 as a foundation layer 3, and a perpendicular recording layer 2, in which Ti, Ta, Pt, B, etc., are added to a CoCr alloy thin-film or a CoCr alloy as a third element, is formed onto the Co, Cr, Ni thin-film. Accordingly, a regenerative output can be improved.

Description

[Detailed description of the invention] [Industrial application fields] 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., the density of floppy disk type magnetic recording devices has been increased.

This method of increasing density can be broadly divided into methods for increasing linear recording density, which increases the recording frequency and increasing the amount of recording per track;
There are two methods: one is to increase the track density, and the other is to increase the number of tracks per disk by narrowing the track pitch and track width.

Among these, as a method for increasing 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, in principle, there is no demagnetizing field, so the higher the recording density, the more stable the magnetization becomes, and the higher the recording density, the easier it is to achieve recording at a density several times that of a medium using the longitudinal recording method.

In order to further improve the linear recording density, a CoCr film or CoCr that does not contain a non-magnetic material such as a binder,
Ti, Ta, and Pt as third elements.

Perpendicular magnetic recording media using metal thin films doped with B or the like 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 approximately twice that of [TPI], servo control of the head is required on the floppy disk driver side. 500
Devices with [TPI] are 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, 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.

Incidentally, 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 enough to compensate for the decrease in reproduction output due to 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.

[Problems to be Solved by the Invention] However, the reproduction output of the perpendicular magnetic recording medium made of this CoCr alloy thin film is only about 2 dB higher than that of the conventional coated medium made of metal magnetic powder.
This required the development of low-noise reproduction amplifiers and signal processing circuits, which was a major obstacle to practical application.

Therefore, one technical object of the present invention is to obtain a perpendicular magnetic recording medium that can improve 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, a CoCrNi layer is formed as an underlayer on the film, and the CoCrNi layer has the following features:
Cr: 15-20wt%, Ni 3-10wt%
, the remainder contains Co, and the Ni concentration decreases from the lower layer to the upper layer, and the Ni concentration is substantially 0 wt% at the top layer.
and the film thickness d is.

200≦d≦1ooo [A thin film of Ongsotromco is formed, and a CoCr alloy thin film or CoCr
Ti and Ta as alloying third elements.

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

The inventor of the present application formed a CocrNi alloy having an easy magnetization axis component in the in-plane direction parallel to the film surface under the CoCr alloy, and provided an underlayer with a N1 concentration gradient from the lower layer to the upper layer. It has been found that the playback output can be improved by

[Example] 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 an oCr 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 reducing reproduction output.

Therefore, as shown in FIG. 3, by forming an underlayer having an easy axis of magnetization in one in-plane direction between the CoCr 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 magnetization in the CoCr film is due to magnetocrystalline anisotropy due to the hCp 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 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.

Furthermore, it does not interfere with the vertical alignment of the CoCr layer.

It is desirable that no interface be formed at the boundary between the CoCr layer and the underlying layer.

This is the result of intensive study by the inventors regarding the above points.

By adopting Ni as the third element and making its composition ratio large in the lower layer and extremely small in the upper layer.

It has been found that the reproduction output of a perpendicular magnetic recording medium using a CoCr alloy thin film can be increased.

Comparative Examples and Examples 1 to 5 will be described in detail below.

FIG. 4 shows a sputtering apparatus used in comparative examples and examples of the present invention.

Two target electrodes facing the center of a rotating disk-shaped substrate holder 10 are installed, and a CoCr alloy target 12 is placed on one side.

A CoCrNi alloy target 13 is attached to the other side.

(Comparative Example) A CoCr thin film with a thickness of 0.3 μl was formed on a polyimide film with a thickness of 30 μl by an RF magnetron method. At this time, the sputtering pressure was 0.1 Pa. The RF power density is 2.74 [W/c-co.

In addition, the CoCr target composition is 17.5vt%:Cr
And so.

(Example 1) In a comparative example, referring to FIG. 1, before forming a CoCr layer, a CoCrNi alloy target 13 and a Co
By Cr target 12, C.

A base layer 3 of CrNi alloy was formed.

At this time, the power applied to each target 12, 13 is changed as shown in FIG.

That is, the initially set power is applied to the CoCrNi target 13 and is lowered after 2 hours. On the other hand, C
The power applied to the oCr target 12 is increased in proportion to the elapsed time from the start of sputtering to form a CoCrNi underlayer 3 having a Ni concentration gradient. After this, C was applied similarly to the comparative example.

Form a Cr layer.

Here, the composition of the CoCrNi target 13 is as follows.

The ratio of Co and Cr in the CoCr target 12 was kept constant, and the amount of Ni was varied. Namely.

(COs2,5Cr 17.5) roo-1N
Lz: X-5[wt% co,
Cr: 18.8wt%, Ni+5vt
%.

Co: Remaining.

The thickness was set to 200 [people].

Further, the sputtering pressure of the base layer 3 was 0.1 [Pa], and the total RF power density applied to the two targets 12.13 was always 2.74 [W/cj].

(Example 2) In Example 1, the composition of the CoCrNi target 13 was as follows: Co: 17.0wt%, Ni: 3vt%,
CO: One was produced as the remainder.

(Example 3) In Example 1, the composition of the CoCrNi target 13 was as follows: Cr: 15.0 wt%, Ni:
10vt%.

Co: 1 was produced as the remainder.

(Example 4) In Example 1, the thickness of the CoCrNi underlayer 3 was set to 50
0 [I thought it was human.

(Example 5) In Example 1, the thickness of the CoCrNi underlayer 3 was changed to 10
00[It was set as A.

FIG. 6 shows the results of measuring composition changes in the depth direction of the medium in Example 1 using Auger spectroscopy.

It can be seen that the interface between the CoCr layer and the CoCrNi layer is not clear, and the amount of Ni gradually increases in the base layer 3, and that the composition ratio is the same as that of the CoCrNi target 13 at the beginning of the formation of the base layer, which is the expected result. is obtained.

Further, for Comparative Examples and Examples, a carbon protective film with a thickness of 100 [A] was formed, and a 2-inch size was punched out to form a 2-inch data disk.

The reproduction output was evaluated when the recording frequency was 9 MHz.

The head used at this time was a MIG type bulk head with a gap length of 0.15 .mu.m, and measurements were taken at a radius of 20 m.

FIG. 7 is a graph showing the relationship between the Ni concentration of the CoCrNi target 13 and the reproduction output for Comparative Examples and Examples 1 to 3.

If the Ni composition ratio is between 3 and 10[vt%], 5[
dB].

Further, for Examples 1 and 4 to 5, the relationship between the thickness of the underlayer and the reproduction output was measured and the results are shown in FIG.

In this example. In the range of 200 to 1000 people, approximately the same reproduction output can be obtained regardless of the film thickness.

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.

[Effects of the Invention] As described above, according to the present invention, a perpendicular magnetic recording medium with significantly increased reproducing force can be produced.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the perpendicular magnetic recording medium of the present invention, FIGS. 2 and 3 are schematic diagrams showing the function of the underlayer 6 in FIG. 1, and FIG. FIG. 2 is a schematic diagram of a sputtering apparatus used in one example. 5 is a diagram showing the formation of the base layer 3 in the embodiment shown in FIG. 1, FIG. 6 is a diagram showing the results of compositional analysis of the embodiment shown in FIG. 1, and FIGS. The figure is a diagram showing the reproduction output of the embodiment shown in FIG. 1. 1...Protective/lubricating oil, 2...Perpendicular recording layer, 3...
Underlayer, 4... Base film, 5... Magnetic head, 6... Magnetic charge, 7... Magnetization, 8... Demagnetizing field, 9...
...Vacuum container, 10...Substrate holder, 1
1... Base film, 12-CoCr target,
13-CoCrNi target, 14.15... sputtering power supply. 16...Matching box. Sputtering time (1) Fig. 5 & I ratio Fig. 6 Bidirectional output [dB] 81111 degrees [wt%] Fig. 7 Reproduction output [dB] 2go400 600 8011 1000 Base layer thickness [1>29 am] Figure 8

Claims (1)

[Claims] 1. A magnetic recording medium in which a magnetic thin film is formed on a polymer film, in which CoCr is used as an underlayer on the film.
A Ni layer is formed, and the CoCrNi layer has Cr:15-2.
0 wt%, Ni: 3 to 10 wt%, balance Co, the Ni concentration decreases from the lower layer to the upper layer, the Ni concentration is substantially 0 wt% at the top layer, and the film thickness d is 200≦d≦ A perpendicular recording layer characterized by forming a thin film of 1000 angstroms, and forming thereon a CoCr alloy thin film or a perpendicular recording layer to which Ti, Ta, Pt, B, etc. are added as a third element of the CoCr alloy. magnetic recording medium.